An ultrashort pulse laser system with precisely controlled output-timing and carrier-envelope phase (CEP) is reported. Recently developed technology Ofl CEP control of a mode-locked laser not only introduced an optical frequency comh in frequency domain hut also gave us a way to generate optical pulses whose oscillating electric field is under a fixed phase relation with the intensity shape. Fortunately, recent advances on optical physics have also showed that sonic types of light-matter interactions become sensitive to the field shape when the pulse approaches a few cycles in duration and has a high peak intensity. Owing to those advances, field-controlled ultrashort pulse generation, based on suh-femtosecond resolution timing-control and sub-radian CEP control of femtosecond lasers, becomes an attractive challenge. Our final goal is to realize a shaped electric field within optical-cycle time scale br researches on light-matter interaction and other future application. CEP control Ofl a mode-locked Ti:sapphire laser is the first step of such a laser system. Trade-off between the accuracy and robustness of the control, and the monitoring technique of CEP br amplilication, will he discussed. Amplification of a CEP-controlled pulse, which is necessary for most of time-domain application, is successfully performed by the CEP monitoring technique. Our chirped-pulse amplifier, that includes a grating-based stretcher/compressor, has a potential to achieve higher-energy amplification of a fixed CEP pulse. Multichannel phase control of spectrally divided ultrashort pulses is applied to dynamic control of pulse-timing and CEP of amplifled pulses. Related results on short-pulse, sub-l3fs, generation by a chirped-pulse Ti:sapphire amplifier, and multicolor phase-coherent pulse sources will be also discussed briefly, showing our on-going efforts to approach the final goal.

High-power solid-state laser programs at China Academy of Engineering Physics have made great progresses in recent years. A three-stage Ti:sapphire laser system, SILEX-I, was completed early in 2004 which could deliver 26-fs pulses at 5TW, 30TW, and 300TW to the corresponding target chambers for diverse applications. SILEX-I has been working very stably since its completion for experiments, demonstrating that it is the most powerful femtosecond Ti:sapphire laser for exploring strong-field phenomena in the world. The SG-III Nd:glass laser facility has been under conceptual design to meet the requirements from laser fusion applications. The SG-III facility is planned to have sixty-four beamlines divided into eight bundles with an output energy more than 100kJ at 0.35μm for 3- to 5-ns pulses. The eight-beamline TIL (Technical Integration Line), the prototype of the SG-III laser facility, has been installed in the new laboratory in Mianyang. The commissioning experiments have been conducted and one of the eight beams has produced 1-ns pulses of 3.0kJ and 1.2kJ at 1.053μm and 0.35μm, respectively. All the eight beamlines will be activated by the end of 2005 and completed in 2006 for operation. Meanwhile, the eight-beam SG-II laser in Shanghai Institute of Optics and Fine Mechanics has been operated for the experiments since 2001 and an additional beam, built in 2004, has been used for plasma backlighting experiments.

Within the last years, modern ultra-short pulse lasers have successfully proven their potential for application in medical tissue treatment in many respects. In dentistry, overheating of the pulp and induction of micro cracks are usually among the most problematic issues which can be solved in this way. An additional benefit can be seen in the possibility of plasma emission spectroscopy as a means of feedback. Up till now it was shown by many authors that the application of picosecond or femtosecond pulses allows to perform ablation with very low damaging potential also fitting to the special physiological requirements. Beside the short interaction time with the irradiated biological matter, lateral scanning of ultra-short pulses following optimized algorithms turned out to be crucial for ablating cavities with the required quality and size, a finding which we also believe to be valid for dental restoration materials. Additionally, out of practical reasons, scanning is necessary to treat larger volumes than just the focal spots typically having dimensions on the order of more than 1 mm³, thereby allowing to realize an "optical drill".

Two independent femtosecond Ti:sapphire lasers are synchronized by using a new passive synchronization design. By enhancing the intracavity cross-phase modulation (XPM), stable synchronization operation of remaining for more than 24 hours with a timing jitter of 0.4fs was demonstrated; the tolerance of cavity length mismatch is larger than 10 micrometers.

We have constructed two kinds of table-top femtosecond terawatt (TW) Ti:sapphire laser systems based on the chirped-pulse amplification (CPA). With a compact design using only two-stage amplifiers, output energies of 36mJ and 640mJ at 10hz repetition rates were obtained with recompressed pulse duration of 25 fs, and 31 fs respectively, corresponding to peak powers of about 1.4 TW and 20 TW. The total pump energy for the last stage is 260 mJ and 2.8 J at wavelength of 532 nm. These results represent a significant efficiency in amplification and a compact configuration in size. By using an adaptive optical system to correct the wave-front distortion of the 20TW laser. we further demonstrated the improvement of beam quality br higher focusable laser intensity.

We investigate femtosecond transient absorption in the visible range in a solution sample of poly(9,9'-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine), TFB, using two-photon excitation at 800 nm (1.55 eV). A rapid probe absorbing process taking place within the temporal overlap between the pump and probe pulses was observed in the whole visible spectral range (430 nm to 700 nm), which resulted from the combination of a transition from 1A_g to mA_g via absorbing one pump and one probe photon and a further transition from mA_g to nB_u state due to the pump-induced transient population on mA_g. A long-lived slow process following the rapid one is interpreted as a combination of 1B_u absorption for transitions to a higher-lying state of kA_g and charge absorption. These excitation and absorption channels, as well as the mechanisms of charge separation, were resolved and evaluated quantitatively by the pump-intensity dependence of the transient absorption dynamics.

A novel 40Gbit/s all-optical high-speed format conversion scheme from nonreturn-to-zero (NRZ) format to return-to-zero (RZ) format based on cascaded second-order nonlinear interactions (SHG+DFG) in a periodically poled LiNbO₃ (PPLN) waveguide is presented for the first time, using a nonlinear optical loop mirror (NOLM). The conversion mechanism relies on the combination of amplification and nonlinear phase shift induced on the signal field by SHG+DFG. The SHG+DFG between pump, and co- and counter- propagating signals in the PPLN waveguide are studied, showing that counter-propagating SHG+DFG can be ignored when quasi-phase matching (QPM) for SHG+DFG during co-propagating interactions. The conversion with the influence of walk-off effect is numerically simulated, the effect of nonlinear phase shift on broadening the conversion bandwidth is analyzed, and an approximately 90-nm conversion bandwidth is achieved, providing the possibility of realizing a broadband tunable NRZ-to-RZ format conversion.

The problem of phase-mismatch-compensation for ultra-broadband OPCPA is first studied theoretically by us, and a scheme for phase-mismatch-compensation is proposed, which is based on the matching of both the group velocity and pulse front between signal and idler by the combination of the no collinear-phase-match and pulse-front-tilt that is accomplished by angular dispersion of the interacting rays. By this Scheme, the phase mismatch to first order in frequency shift can be completely compensated, and then an ultra-broadband OPCPA is realized. It is shown that the phase mismatch to both first and second order can be completely compensated simultaneously in some cases, and this leads to an extremely broadband spectral width. Therefore the important criterion for constructing an ultra-broadband OPCPA that both pulse-front and group-velocity between signal and idler are exactly matched simultaneously. Finally, specific numerical calculations and simulations are presented for BBO-OPCPA with type-I noncollinear angularly dispersed geometry.

We report the experimental research on the measurement and controlling of carrier envelope phase offset (CEO) with a home-made femtosecond Ti:sapphire laser, the beat frequency with a signal to noise ratio of as high as 45 dB is obtained with standard self-referencing technique. Locking the beat signal to the TV-Rb frequency standard by a phase-locked loop electronic circuit, a simple compact frequency comb was established. To further control the CEO with the technology of differenced frequency generation, we develop an ultra-broadened bandwidth femtosecond Ti:sapphire laser by balancing the dispersion with chirped mirrors, spectrum of covering from 600 nm to 1050 nm was observed. It will enable us to measure and control the CEO without photonic crystal fiber.

The coupled equations of second harmonic generation of ultra-short pulse through a nonlinear optical crystal CsLiB₆O₁₀ is solved using the Fourier method. The second harmonic pumped by 532 nm, 50 fs fundamental wave through CsLiB₆O₁₀ is simulated numerically. The results point out that the pulse of second harmonic is widened and the harmonic shape is deformed because of group velocity mismatch and group velocity dispersion. The pulse of SHG is widened to 100 fs and the pulse shaping of SHG is delayed to 50~60 fs when the CsLiB₆O₁₀ crystal length is 0.5 mm.

With excellent temporal resolution ranging from nanosecond to sub-picoseconds, a streak camera is widely utilized in measuring ultrafast light phenomena, such as detecting synchrotron radiation, examining inertial confinement fusion target, and making measurements of laser-induced discharge. In combination with appropriate optics or spectroscope, the streak camera delivers intensity vs. position (or wavelength) information on the ultrafast process. The current streak camera is based on a sweep electric pulse and an image converting tube with a wavelength-sensitive photocathode ranging from the x-ray to near infrared region. This kind of streak camera is comparatively costly and complex. This paper describes the design and performance of a new-style streak camera based on an electro-optic crystal with large electro-optic coefficient. Crystal streak camera accomplishes the goal of time resolution by direct photon beam deflection using the electro-optic effect which can replace the current streak camera from the visible to near infrared region. After computer-aided simulation, we design a crystal streak camera which has the potential of time resolution between 1ns and 10ns.Some further improvements in sweep electric circuits, a crystal with a larger electro-optic coefficient, for example LN (γ₃₃=33.6×10^-12m/v) and the optimal optic system may lead to better time resolution less than 1ns.

We report a preliminary experiment result of poling in a femtosecond-laser-treated LiNbO3 (LN) crystal. Because of the precision of the femtosecond laser machine, we can control the width and depth of snicks exactly. Then the high-voltage electric field was operated on +z side of the LN crystal. The visible poling pattern was observed by a microscope and machining parameter influences the electric field distribution in the crystal. This approach does not need expensive masks and the periods of PPLN can be adjusted flexibly. Although the mechanism of core formation is not very clear yet, we believe that it would provide a novel technique of making prototype PPLN and other periodically poled crystals.

A stable passively Q-switched Nd: YVO₄ laser was demonstrated by use of a GaAs absorber grown at a low temperature (LT GaAs absorber) by the Metal Organic Chemical Vapor Deposition (MOCVD) technique, as well as an output coupler. The shortest pulse duration measured was about 12 ns with a single-pulse energy of 4.84 μJ, and the highest average output power is 1.16 W. The repetition rate is 360 KHz, which corresponds to the pump power of 2.8W.

We present a fiber based source of entangled photon-pairs in the 1550 nm telecom band that can be integrated into the existing fiber network and is well suited for quantum information processing. With this source we have demonstrated the generation, storage, and long-distance distribution of polarization entanglement in standard optical fiber. We have also investigated the origin of the large number of accidental coincidences in the experiments, which has been proved to be Raman scattering, and discussed how to suppress the Raman scattering to improve the quality of the fiber source.

CO₂ and YAG lasers are routinely capable of producing cw output powers in the range of sub-W to multi-kW and as such have become the mainstay of the laser cutting and welding industry. Despite numerous advancements in their design, these lasers are still typified by poor wallplug efficiencies (typically 1-10%) and/or relatively poor optical beam qualities. On the other hand, recent developments in laser diode technology, fiber design and beam combining techniques have meant that cladding pumped ytterbium-doped fiber lasers have attracted growing interest as a route to highly efficient (20-40% wallplug efficiencies), high output power, high beam quality (near-diffraction limited) lasers for a vast array of material processing applications. More specifically fiber lasers have a number of distinct advantages over their more conventional alternatives including size, reliability, wavelength selectivity, heat dissipation, wallplug efficiency, and operational cost. Furthermore, they can be operated without the need for active cooling or optical alignment. In this paper we review the recent progress in fiber design that is facilitating the scalability of the output power of fiber-based lasers and amplifiers.

In this paper the photonic crystal fiber (PCF) with square-lattice array in a silica matrix has been put forward. The PCFs studied in this paper have a solid core, obtained by introducing a defect that is by removing two holes at the center of the fiber cross section and with smaller air-holes in the same direction. For the different wavelengths in the range between 700 nm and 1600 nm, the effective index n_eff of the PCF fundamental mode has been obtained by the fast multipole method. The model field, birefringence, and confinement loss of the fibre fundamental mode are simulated. It is found that lower confinement loss and higher birefringence can be realized in the condition of fewer rings of air holes. The simulation results in this paper are important for instructing the fabrication of birefringent photonic crystal fibers.

Tunable photonic bandgap fibers (PBGFs) were theoretically investigated by using the vector plane-wave expansion method and the vector finite element method. The tunable PBGFs are fabricated by filling a high-index material in the air holes of index-guiding photonic crystal fibers. The wavelength dependence of leaky loss and group velocity dispersion (GVD) has been illustrated. We show the leaky loss in the tunable PBGFs can strongly depend on the refractive index of filled material due to the photonic bandgap effect. The tunable attenuator which operates at 1550 nm is designed based on this PBGFs.

Novel highly birefringent photonic bandgap fibers (PBGFs) are obtained by filling high index material in the air holes of total internal reflection birefringent photonic crystal fibers. The effect of filling high-index material on the transmission characteristics has been theoretically investigated. The photonic bandgap has been achieved by using the plane-wave method. Moreover, the polarization mode dispersion (PMD) has been studied by a full-vector finite-element method. Numerical results show that very high PMD with magnitude of order of 10^-10 has been respectively acquired, which is much higher than those of the non-filled fibers. Furthermore, strong coupling between surface modes and the fundamental modes has been found in the bandgap of the birefringent PBGFs.

In this work, 10 GHz over 58 nm 20 dB bandwidth supercontinuum (SC) is generated in 4.5 km dispersion-shifted fiber (DSF) pumped by a 10 GHz regeneratively mode-locked fiber laser (RMLFL). The optimized SC with 51.5 nm 20 dB bandwidth is obtained by properly adjusting the pump power. A 25 nm spectral region from 1535 nm to 1560 nm and a 12nm spectral region of 1567-1579 nm with ±3 dB uniformity are generated. 10GHz, over 30 channels were sliced by an array waveguide grating (AWG) with 100 GHz channel spacing. Timing jitter of each channel is less than 1.25 ps.

A novel type of distributed fiber optic sensor is presented to detect and locate a time-varying disturbance along the whole fiber length. The sensor consists of a Mach-Zehnder interferometer (MZI) where two directional optical signals are simultaneously traveling. This is achieved by a fiber-loop in the configuration, causing one MZI to operate as two co- and counter- propagating interferometers. The sensor is illuminated by only one continuous-wave laser, which is different from the conventional scheme. The phase shift caused by any disturbance around the fiber is detected and converted to the information on the perturbation position and amplitude, which can be determined by combining two phase signals from the above device. In addition, passive homodyne demodulation with application of a 3×3 fiber optical coupler for recovering a signal of interest from the MZI is also described. This technique can yield a large dynamic range with phase amplitudes for its symmetry. Also, high speed digital processing (DSP) technology is used in the sensor system, which can carry out all operations in real time and promote the resolution of localization. The system has capability for cross-correlation algorithm and fast Fourier transform (FFT) analysis of the detected disturbance signals, for the sake of determining the disturbance position and type. Finally, a positional resolution better than 100 m has been theoretically discussed and experimentally demonstrated in a system over 6.8 km fiber length.

Because an ytterbium-doped fiber amplifier has broad-gain bandwidth, high output power, and excellent power conversion efficiency, it has attracted much attention. Based on two-level model, the gain and propagation characteristics of Yb-doped fiber amplifier at 1064nm by dual-wavelength pumping (910nm and 975nm) were analyzed after introducing the overlapping factors and ignoring the effect of ASE and the fiber loss. In order to compare, other two pumping schemes were discussed, namely, 910nm pumping and 975nm pumping respectively. The differences between the Yb- and Nd-doped fibers for amplifying the light of 1064nm were also discussed.

We report a new fiber-optical solution concentration sensor based on an etched long-period fiber grating with one opening head coated with a silver film, which is written symmetrically by three beams of focused high-frequency CO₂ laser pulses in a standard single-mode fiber (Corning SMF-28). This sensor is tested with two kinds of solution, i.e. sugar and CaCl₂, and the experimental results show that this etched fiber-optical sensor with one opening head is flexible to operate and has very high resolution. The resolution of this sensor increases with approximate linearity, as the concentration of solution increases, and the resolutions for sugar solution at low and high concentrations are 1.65 (g/l) and 1.36 (g/l), respectively. Its average resolution has been improved above 28% after the cladding radius of this sensor is reduced to 61μm by etching with HF acid. The method of etching with HF acid can also be used to tune the resonant wavelengths of a long-period fiber grating.

A novel super-fluorescence fiber source (SFS) in the wavelength range that covers the C+L-band with stable spectrum, high output power and high slope efficiency is demonstrated. The topology consists of two stages: the first stage provides primarily the L-band gain spectrum whilst the second is solely for the C-band. These two stages are combined in series. We merely used the low erbium-doped fiber (EDF) 10.8m long as a gain medium in the second stage, which was pumped backward by a 980nm semiconductor laser diode (LD). As a result, the Amplified Spontaneous Emission (ASE) spectrum had a threshold of 5.1mW and a slope efficiency of 13.48% in the C-band. With a 980 nm LD pumping forward at 11-m-long moderate EDF and 58-m-long low EDF in series, L-band ASE was yielded with 52.3 mW threshold and a slope efficiency of 35.82% in the first stage. The ASE in the L-band was put into the second stage through an isolator and combined with C-band ASE as an output then a broad ASE spectrum of C+L-band was observed. The maximum output power of the C+L-band source was 33mW (15.3dBm) and its power stability was better than ±0.02 dB. Through the optimization of fiber parameters and the adjustment of pumping power in both stages, the flatness of ASE spectrum was improved. The optical bandwidth for the SFS output power, which ripples in 3 dB, was 63.7 nm (1536.92-1600.62 nm) of optical bandwidth without gain flattening filter.

In this paper the parameters of a CW double-clad fiber laser are theoretically analyzed, which is of important references to designing the kindred double-clad fiber lasers. This paper also offers a personalizing design scheme of double-clad fiber lasers, with the influence of some important parameters on the output power clarified.

Based on the analysis of conventional L-band EDFA we demonstrate a novel structure that improves the L-band amplification performances. In conventional L-band EDFA, 35nm (±1dB) flattened amplification bandwidth from 1565 to 1600 nm is obtained. Small signal gain of 25dB is achieved at 1590 nm with input power of -30dBm and the saturated output power reach to 10dBm. The linear relation between pump power and signal power are demonstrated experimentally. By utilizing a fiber Bragg grating (FBG) with center wavelength of 1550 nm, the population inversion of EDFA is intensified, which gives rise to gain improvement. Experimental results show that the signal gain is enhanced by the FBG by more than 8dB. The use of FBG has also shown a better performance in gain clamping. The amplifier gain is clamped at 25dB with a gain variation of less than 0.5dB for input power as high as -15dBm.

The dynamics of a two-mode model of the erbium-doped fiber laser is analytically and numerically investigated. Apart from the intrinsic nonlinearity of a two-mode laser, the existence of erbium ion pairs introduces a supplementary nonlinearity with a saturable absorber action. The laser is described through six coupled differential equations. Steady states are analyzed, their dependence on the laser parameters, and the onset of the self-pulsing and chaotic states is pursued.

In this paper, the application in return-zero (RZ) light source based on regeneratively mode-locked fiber laser (RMLFL) is demonstrated. By using Mach-Zehnder modulator and pseudo-random code modulation, the back-to-back eye-diagrams with good performances are obtained and RZ format light source with pulse duration of 5ps based on RMLFL is achieved, which quite meets the requirements of 10 Gbit/s long haul transmission. Furthermore, such a 10 GHz RZ source could be multiplexed into 40 GHz RZ light source simply by 4 fold optical time division multiplexing (OTDM).

This paper begins with a brief description of the nonlinear Schroedinger equation (NLSE). Then split-step Fourier transform method (SSFT) is used to simulate the pulse evolution when high order group dispersion and high order nonlinear effect are considered. Different phenomena induced by high order group dispersion are discussed, where the effect of the polarity of the pulse chirp, the third-order dispersion coefficient, and the effect of the high-order dispersion on self-phase modulation (SPM) are also discussed, respectively. For the high power density in the wavelength diversion multiplexing (WDM) system, some phenomena induced by high-order nonlinearity such as self-steepening are simulated, and qualitative analysis is given at the same time.

Using a plane wave expansion method, we numerically show that the bandgaps of honeycomb photonic bandgap fibers can be effectively tuned by interstitial air holes. It is shown that the number of bands varies with the filling fraction of interstitial air holes, and also that the width of the bands can be substantially increased by interstitial air holes. For a honeycomb photonic bandgap fiber with a large air filling fraction, the widths of the primary and secondary bandgaps are increased twice by interstitial air holes. In the case of a small air filling fraction, the relative sizes of the two gaps can reach up to 11.7% and 6.4% using interstitial air holes. Therefore, using interstitial air holes proves to be an effective way to tune the bandgaps of honeycomb photonic bandgap fibers.

Lithium niobate-based Y junction waveguide multifunction integrated optic chip (M-IOC) is one of core optic components in fiber optic gyro. Its performances have very important influences on fiber optic gyro (FOG) accuracies. Fully understanding its performances in FOG will help us to further improve fiber optic gyro performance (bias drift < 0.01°/h). The paper focuses on the studying of application features of Y-junction integrated optic chip(Y-IOC) in FOG with bias drift less than 0.01 °/h. It also describes the system test methods for checking integrated optic chip performances. Interesting research points are: Y-IOC optic technology and its application in FOG, features of Y-IOC in FOG, the corresponding test system and the matching of Y-IOC with FOG system. Research results show: Y-IOC optic performances, Y-IOC electrical characteristics, as well as the matching between electrical circuits of FOG system and electrical features of Lithium niobate- based Y junction waveguide multifunction integrated optic chip all together play very important roles in achieving high performances of FOG.

A Fiber Bragg Grating (FBG) sensor demodulation system of matched Bragg gating with a simple structure is studied. The cantilever is designed by using acryl glass, and the wavelength's linear tuning of FBG is operated by tuning the cantilever of acryl glass. The sensor signal of Real-time detect is detected by using an oscilloscope after the optical sensor signal enters the photoelectric detector. Demodulation operation of matched-gating is achieved. Wavelength resolution of 2.33pm is obtained. The advantages of this demodulation system is simple structure, electromagnetic interference resistance, high wavelength resolution and high rate of cost performance, so it has a great application prospect.

In this paper, we propose and demonstrate a novel torsion sensor based on a long-period fiber grating (LPFG) induced symmetrically by three beams of focused high-frequency CO₂ laser pulses (20~24 kHz). Experimental results show, when the LPFG is twisted clockwise, the resonant wavelength shifts toward shorter wavelengths, and the peak loss decreases. When the LPFG is twisted anticlockwise, the resonant wavelength shifts toward longer wavelengths, and the peak loss increases. The resonant wavelength and the peak loss are all similarly proportional to the twist angle applied. Based on this LPFG, a new kind of fiber-optic torsion sensors can be made, which can not only directly measure the torsion angle, but also determine the torsion direction simultaneously by means of measuring the shift of the resonant wavelength and/or the peak loss of the LPFG.

It is well known that PCFs, compared with traditional fibers, have many special characteristics. Because of these, PCFs have been used in sensors. Based on the principles of traditional fiber sensors, this paper analyzes the probability of applications of PCFs in gas or liquid sensors. Due to the multi-hole properties of the PCFs, we can make some gas or liquid sensors by putting different gases or liquids into its air-hole. In this paper, the sensitivity of PCF sensors was simulated by the multipole method. By changing the core radius of PCFs or the gas fraction in the hole of PCFs, we can improve their sensitivity. Due to the superiority in their configuration, the research on PCF sensing characteristics will surely promote the development and application of the new-type sensors and other photoelectron devices.

An efficient shooting algorithm based on the simple-shooting method and the modified Newton-method for fiber Raman amplifier design is proposed. By introducing the Broyden's rank-one method, the time-consuming calculation of the Jacobian matrix is dramatically relieved. Numerical simulation results show that the simulation efficiency of the proposed method has been improved more than 70 percent compared with the conventional shooting method.

A new numerical optimization method assisted by functional model and improved Newton's iterations is proposed. The method would be applied to the pump power configure optimal design for the gain flatness optimization in the laser-diode discrete Fiber Raman amplifier (FRA). Compared with other optimization algorithms, the proposed improved Newton's iteration has fast convergence speed and good stability. So the method can exploit better solutions and greatly shorten the amount of run time. Two samples show the feasibility of the method with different initial variables. The comparison with Genetic algorithm (GA) is obtained.

In this paper, a numerical method is presented to design a biconical waveguide. We use this method to calculate the transmitted and radiated power of the biconical waveguide in an integrated acousto-optic modulator, then we plot the normalized power loss curves versus the taper length and get the optimum design.

In this letter, a S-band discrete Raman fiber amplifier(RFA) with the maximum net gain of 18.3dB was obtained. Using the gain flattening filter based on a cascaded long-period fiber grating (LPFG), the gain profile of this RFA was flattened to within ±1dB in the wavelength range from 1 480 nm to 1 515 nm, and an average gain of 11.3dB was achieved.

A broadband source (1520-1620nm) with output power of more than 200mW is achieved using only a single-wavelength pumping scheme dependent on the combined effects of stimulated Raman scattering, parametric process, and Erbium-doped fiber amplification.

Photonic-crystal fibers provide efficient nonlinear-optical transformations of femtosecond Cr: forsterite laser pulses, delivering linearly chirped frequency-shifted broadband light pulses, optimized for pump-probe nonlinear absorption spectroscopy of molecular aggregates. The blue-shifted output of a photonic-crystal fiber with a spectrum stretching from 530 to 680 nm is used to probe one- and two-exciton bands of thiacarbocyanine J aggregates in a polymer film excited by femtosecond second-harmonic pulses of the Cr: forsterite laser.

Using an efficient, full-vectorial numerical simulation method, we analyze the existent conditions of the photonic bandgap (PBG), which is further demonstrated through experimental research. We utilize the method of transmission spectrum to measure the hollow-core microstructure fibers (HC-MSFs) in the visible and near infrared regions. The signal is obtained by detecting light from the end of the fiber. The experimental results indicate that there are several strong transmission bands in the near infrared region, but hardly any bandgaps in the visible region. Furthermore the attenuation in the visible wavelength is very considerable. The parameters of the HC-MSFs structure used in the measurement are the distance of nearest air holes pitch Λ (2.65μm), the diameter of air holes in the cladding d (2.10μm), and the central air core diameter (8.37μm). The spectrum positions of the bandgap in the spectrogram are 2297nm, 2406nm, and 2525nm, respectively. The repetition of the experimental results is fine.

The Stacking-capillary Method is widely used in the fabrication of the Micro-structure Fiber (MSF). We describe an improved stacking-capillary method, which can fabricate the MSF without interstitial holes. The method includes several steps. Firstly, the MSF preform is made by the stacking-capillary method; secondly, the MSF preform is put into the high temperature furnace to heat at 1600°, then the positive pressure is produced into the capillaries by adding air, every three adjacent capillary holes are expanded in the preform, and the interstitial holes are eliminated, all the capillaries are fused together, although the round capillary have changed to hexagon, the size of the prefrom does not change, and still keeps very good structure. The step of eliminating the interstitial hole can help to keep the MSF structure during drawing fiber. We get well results by the Improved Stacking-capillary Method.

The light is the ultimate energy source for the life on the earth and also it is with the help of light that we see and understand the world surrounding us. The energy quanta are called photons. In addition to illuminating, imaging, and spectroscopy, a typical example of the recent uses of photons in our daily life is optical communication. A more and more important new role that photons are playing is manufacturing, particularly in three-dimensional micro-nanofabrication on the basis of nonlinear photon-matter interactions. This article reports our recent progress in this research direction: the challenge to the spatial resolution of fabrication, and the utilization of the technology on nanophotonic and micro-nanomechanical devices.

We report on an experimental investigation into the recording and readout of 3D high-density optical data storage in transparent optical glasses using a femtosecond laser. A compact Ti:sapphire ultrafast laser amplifier as writing laser was developed to output 100mW 2.1ps at 1KHz with 1W pump laser. Laser pulses modulation is realized by modulating two circuits of trigger pulses signal which are used to control laser pulses trapping and switching out from cavity, respectively. A formatted and coded writing was realized in fused silica and doped polymethylmethacrylate(PMMA) bulk. A phase-contrast and a reflection confocal reading system with software are developed for optical readout of multi-layer data bits in parallel.

A new laser plasma technique for non-vacuum deposition of thin films has been developed recently. This technique was successfully applied to deposit hard carbon coatings on steel substrates. The obtained diamond-like carbon (DLC) coatings with amorphous structure demonstrated high nanohardness and good adhesion to the substrate. Here we present new experimental data concerning parameters of the produced carbon plasma and features of the plasma-substrate interaction, which are necessary for further progress of this technique. Spectroscopic study of the plasma emission was performed for picosecond and nanosecond laser pulses at different wavelengths (λ=1078 nm, 539 nm and 248 nm). The laser plasma composition was studied and conditions for the occurrence of low-threshold air breakdown near the target surface were determined. The ranges of the substrate-target distances, which ensure carbon film deposition or plasma etching of the substrate, were determined. The revealed influence of the laser pulse energy, pulse duration and wavelength on the plasma-substrate interaction is reported.

Dynamics of self-pumping photorefractive double phase-conjugate mirrors is considered. It is shown that depending on experimental conditions as phase-conjugation with efficiency up to 60-80 % as formation of unstable structures of soliton-like filaments can be realized.

New porous silicon preparation technique has been suggested and realized with using vapor etching of silicon in iodine and HF contained vapors. It has been shown that vapor etching allows the preparation of luminescent porous layers on heavy doped (n⁺⁺ and p⁺⁺ type) silicon. Comparison of Raman and CW excitation PL measurements of vapor etched porous layer with typical anodized luminescent porous silicon indicated that they have in general similar structural and PL properties. Time resolved photoluminescence measurements reveal however that excitation recombination for iodine contained vapor etched samples is two times faster with higher photoluminescence efficiency, which can be interpreted as increasing of radiative recombination rate for luminescence centers in new nanocrystalline silicon.

Pulsed Laser Deposition of indium tin oxide in the femtosecond regime has been performed in our laboratory. Plume diagnostics has been carried out by means of a fast Intensified Coupled Charge Device (ICCD) camera. Optical emission spectroscopy has been applied to characterize the transient species produced in the femtosecond regime. The time evolution of emission lines has been discussed and compared with that obtained for nanosecond regime. The films, deposited on glass substrates, has been analysed by scanning electron microscopy, energy dispersive x ray analysis, x ray photoelectron spectroscopy and x ray diffraction. The results obtained from femtosecond ablation show that the processes in the short pulse regimes are very different from the nanosecond one. In particular the plume angular distribution shows a characteristic high cosine exponent and the composition of the deposits is completely stoichiometric and independent from the laser fluence, even if to obtain crystalline films a substrate temperature of 600 °C is needed. Preliminary data indicate that the deposited films are suitable for gas sensor applications.

It is investigated that the duration of stimulated Brillouin scattering (SBS) amplification of Stokes pulses is smaller than the acoustics lifetime and the oscillation period of hypersound with the nanosecond pulse as pump light. In the experiment, the Fluorinert (FC-72) is used as the Brillouin amplification medium, the Stokes pulse duration less than 1/4 of oscillation period of hypersound of FC-72 as seed pulse is achieved by two-stage SBS compressor to compress 8ns laser pulse. The experiment and simulation show that, in this case, their energy amplification is efficient, but the duration of amplified pulses is longer than the initial seed pulse. Simulation results of higher energy than the maximum energy in the experiment show that at sufficient high pump or initial seed pulse power intensity, the duration of amplified pulses can be no larger than the initial seed pulse duration., even less than the seed pulse duration.

A novel cascaded χ⁽²⁾ wavelength conversion of picosecond pulses based on sum frequency generation and difference frequency generation (SFG+DFG) is proposed and experimentally demonstrated in LiNbO₃ waveguides. The signal pulse with 40-GHz repetition rate and 1.57-ps pulse width is adopted. First of all, high conversion efficiency about -18.93dB can be achieved with low power level required for both two pump lights, which is greatly enhanced approximately 8dB compared with the conventional cascaded second-order nonlinear interactions (SHG+DFG) with a single and much higher power pump. Secondly, the wavelength of the converted idler wave can be tuned from 1527.4 to 1540.5nm when the signal wavelength is changed from 1561.9 to 1548.4nm, and about 13.1nm converted idler bandwidth is achieved with the conversion efficiency higher than -31dB. Thirdly, two pump wavelengths can be separated as large as 17.3nm. Meanwhile, when one pump wavelength is fixed at 1549.1nm, the other can be tuned within a wide wavelength range about 7.6nm with the conversion efficiency higher than -34dB, which is much larger than that in the SHG+DFG situation. Finally, the temporal waveform of the converted idler pulse is observed with rather clear appearance achieved, and no obvious changes of the pulse shape and width are found compared with its corresponding original injected signal, showing that our proposed scheme exhibits a very good conversion performance.

Theoretical analysis on phase matched second-harmonic generation (SHG) in a more general manner is presented from the viewpoint of modulation of the nonlinear coefficient. The conventional quasi-phase matching (CQPM) is firstly analyzed, showing a noticeable result that the intensity of second-harmonic wave grows most rapidly at odd times of half Lc, i.e., Lc/2, 3Lc/2, 5Lc/2, etc., but most slowly at even times of half Lc, i.e., 0, Lc, 2Lc, 3Lc, etc. Based on which, a new scheme to realize phase matched SHG by modulating the nonlinear coefficient using alternating "+", "0", "-", "0" every Lc/2 is proposed with the analytical expressions for conversion efficiency (η) and conversion bandwidth (Δ_FWHM) derived. Compared with CQPM, it is found that the same Δ_FWHM approximately 5.566/L, and at the same time, a much more effective η can be achieved when ignoring partial waveguide in which the nonlinear coefficient is "0", however, when considering it there is a 3dB penalty for η. Furthermore, a much more general scheme to realize phase matched SHG is proposed, also using alternating "+", "0", "-", "0" but with variable duty cycle. We present the analytical expressions for η and Δ_FWHM , with the result showing that Δ_FWHM keeps constant, i.e., 5.566/L. In addition, the fabrication tolerances are discussed, and our proposed scheme exhibits a better performance.

A new method to reduce the residual pulse peak in stimulated Brillouin scattering (SBS) optical limiting by an injected seed is presented. The pulse shapes of the transmitted pump beam are studied for various delay times and injected seed powers theoretically. The numerical simulated results show that the height of the residual pulse peak can be controlled by changing the delay time and injected seed intensity. Experimentally, various optical limiting pulse shapes with different heights of the residual peak are observed by changing the delay time and intensity of the seed injected into the SBS optical limiter. The experimental and theoretical results show that the residual pulse peak in SBS optical limiting can be controlled by the delay time and power of an injected seed.

Based on the multi-axial theory of stimulated Brillouin scattering (SBS), a group of coupled wave equations without limitation to the mode separation of a laser is deduced when the random initial phases of the axial modes are introduced for SBS pumped by a free operation laser. The coupling coefficient between two axial modes is obtained, and the dependences of the threshold and reflectivity of broadband SBS on the bandwidth, the mode number, the mode separation of the laser, are simulated numerically. The SBS threshold and reflectivity are dependent not only on the laser bandwidth, but also on the mode number and the mode separation of the laser.

The issues of modeling the semiconductor laser with circuit elements have been addressed by several authors. Previously reported laser models are based upon rate equations and many relations between electron and photon. This needs the deep understanding of the clear physical meaning of all variables and the electrical and optical properties of the active region of a semiconductor laser diode. The relations and the formulas are very complex and the model's parameters are hard to get. In the previous models, node voltages are used as circuit variables. In practice the LD is powered by a constant or pulse current source. The node voltages are only measurable variables and decided by the input current for a ready-made LD. So taking the input current as the circuit variable is very simply and easy to understand and use. In this paper a circuit model of DHLD has been developed from rate equations and the well known models. Simulink module is built according to the rate equations. The input current is the only variable for the module. The transient response of the LD model is plotted. The simulating results such as transient and frequency responds agree well with the reported data.

Characteristics of transmitted temporal profile of active stimulated Brillouin scattering (SBS) optical limiting are studied. Methods of impairing transmitted residual peak power and shortening the delay time of SBS are proposed. Based on coupled wave equations of SBS process, physical models of optical limiting based on active SBS are constructed. Using an implicit finite differencing in time and a downward differencing scheme in space, theoretical calculation models of active SBS limiting for numerical simulations are built up. Three parameters, i.e. residual peak power, delay time and limited power are defined renewably to characterize active SBS optical limiting. The relationship of transmitted temporal profile to seed peak power is obtained by numerical calculations. The influence of the injected seed power on transmitted residual peak power is analyzed in detail. It is shown that the residual peak power is weakened with strengthening of the seed power. By selecting suitable power of seed, residual peak is removed and consequently the ideal flat pulse output is achieved. On the basis of theoretical analysis, active SBS optical limiting temporal characteristics are examined experimentally with a 20 ns Nd:YLF laser and one nonlinear medium (CCl₄). The experimental results are compared with analytical and numerical calculations.

Raman Spectroscopy is a molecular vibrational spectroscopic technique based on the Raman effect, which is characterized by the frequency shift that caused by interactions of molecule and photon and shows the information in molecules. There are many advantages to study the sample with Raman spectroscopy, such as simple system structure with relative lower cost, wide variety of detectable masses, nondestructive detect for multicomponent sample, good sensitivity, feasibility of real-time analysis and online examination assisted with optical fiber and computers, etc. As a powerful tool for quantitative or qualitative analysis, Raman spectroscopy has been employed to solve certain unique problems in chemical and environmental analysis and in industrial process monitoring and control. Now, there are many kinds of organic contaminants, particularly aromatic molecules, in industrial waste water, so it is essential to determine and monitor these contaminants. This paper analyzed the Raman spectra of benzene and benzene derivatives (toluene, ethylbenzene, chlorobenzene, and nitrobenzene) in detail, and assigned their Raman identified spectra. The results show that Raman spectroscopy is useful to analyze benzene derivatives in waste water.

Serial coherent laser beam combination is studied using one-dimensional transient model of stimulated Brillouin scattering (SBS). Beam combination is achieved by transferring the energy of several pump beams to one Stokes beam. The pulse-width of the Stokes beam, which is approximately equal to that of the pump, can be kept constant by adjusting the meeting position between Stokes beam and pump beams in the cell. Numerical simulation is made for the condition that power density of Stokes beam is larger than that of the pump beam. Simulation results show that the major factors that determine the energy extraction efficiency and the critical value of beam combination are the absorption of the medium and the length of SBS cell. The absorption loss is found to play a leading role, so that the overall energy extraction efficiency and the critical value of beam combination can be increased by using shorter SBS cells and/or medium with lower absorption rate. The simulation chooses CCl₄ as target medium. The SBS cell length is 20cm; 20 beams (wavelength 1064nm, energy 1J, pulse-width 10ns, beam-area 1cm2) are combined in serial, one of which generates the Stokes seed, others are the pump beams. In order to keep the power density below 100MW/cm² to avoid being more than threshold of SBS, the Stokes beams and pump beams must be expanded. The output beam of ~10J energy, ~10ns pulse-width, ~10cm² beam area is obtained.

We show that both the spectral-temporal and temperature "anomalies" of experimental data, obtained by pump-probe spectroscopy of HTSC compounds, can be interpreted with taking into account inter-band electronic transitions and a "frozen" energy gap in the sample electronic spectrum.

The results from nano indentation is employed to study the mechanical behaviour of materials at nanometric scale. Based on the extensive experiments using nano indentation, a new phenomenon is discovered in understanding micro cracking on single crystal silicon. Thus, a new method is proposed in evaluating the micro cracks occurring, i.e., an increasing rate of absorbed energy, which is significant in examining the brittle-to-ductile transition of single crystal silicon. This method provides a simple approach in understanding the micro cracks, while it is very tedious in conventional method. Experimental studies reveal that the increasing rate of absorbed energy in nano indentation presents an identical correlation to the surface cracks on single crystal silicon surfaces.

Laser plasma technique for CVD synthesis of diamond in open air that dos not demand a vacuum or reaction chamber has been developed. Laser plasmatron, based on 3 kW cw CO₂ laser and presented in this work, was used for CVD of diamond films on tungsten and molybdenum substrates with deposition area of about 3 - 4 times larger then plasma jet cross-section. Different modes of laser plasmatron operation with substrate movement relative to plasma core are considered. Possible directions of further investigation of laser-induced plasma CVD of diamond on large area are discussed.

Laser acupuncture defined as the stimulation of traditional acupuncture points with low-intensity, non-thermal laser irradiation and the therapeutic use of laser acupuncture is rapidly gaining in popularity. As recovery instrument, physiotherapy instrument has a long curing period but perfect curative effect; furthermore, the treatment scheme needs to he revised on the basis of exchanges between patients and medical staff. In this paper a new laser acupuncture instrument based on Internet is designed. This multi-functional visual physiotherapy system based on embedded TCP/IP protocol, is further developed, which can realize visual real-time communication between patients and doctors with the help of Internet. Patients can enjoy professional medical care at home. Therefore, the equipment is suitable to those where specialists are needed; such as villages, towns, communities, small private clinics, and those families applicable. For such equipment, the key is to design an embedded networked module. The solution of this paper is to design the Ethernet interface based on DSP.

It has been very common that a pulse laser is used in derma surgery based on the theory of "Selective Photothermolysis". This method has also been accepted as the best way to treat the pigments by the medical textbook. A kind of double-pulsed laser which gets the name by two pulse output at one pumping process is developed for derma surgery lately, and this kind of laser has been proved more effective and safe than single-pulse laser. We also develop a multiple work mode YAG laser including two double-pulsed modes at 1064nm and 532nm, two single-pulsed modes at 1064nm and 532nm, and one free-running mode at 1064nm. Considering availability, security and reliability of the laser as a surgery machine, some important subsystems of the laser are optimized carefully, such as Q-switch driver, wavelength-switching system, power supply, and control system etc. At last we get a prototype laser which can run for longer than 30 minutes continuously, and output Max10 pulse per second (pps) with Max800mJ energy at 1064nm double Q-Switch mode, or Max400mJ at 532nm. Using double pulse mode of the laser we do some removal experiments of tattoos and other pigments, and obtain good effect.

Since the first laser-needles acupuncture apparatus was introduced in therapy, this kind of apparatus has been well used in laser biomedicine as its non-invasive, pain- free, non-bacterium, and safetool. The laser acupuncture apparatus in this paper is based on single-chip microcomputer and associated by semiconductor laser technology. The function like traditional moxibustion including reinforcing and reducing is implemented by applying chaos method to control the duty cycle of moxibustion signal, and the traditional lifting and thrusting of acupuncture is implemented by changing power output of the diode laser. The radiator element of diode laser is made and the drive circuit is designed. And chaos mathematic model is used to produce deterministic class stochastic signal to avoid the body adaptability. This function covers the shortages of continuous irradiation or that of simple disciplinary stimulate signal, which is controlled by some simple electronic circuit and become easily adjusted by human body. The realization of reinforcing and reducing of moxibustion is technological innovation in traditional acupuncture coming true in engineering.

Static and dynamic light scattering are used to measure molecular parameters of γ-globulin in solutions in the presence of sodium and potassium ions. Intermolecular interactions coefficients and molecular masses of scattering particles in the protein water solutions were determined as a function of pH and ioning strength by static light scattering. In the proteins solutions containing Na⁺, molecular mass of scattering particles is constant, but in the case of proteins solutions containing K⁺ ions molecular mass of scattering particles increases in vicinity of isoelectric points of proteins Translational diffusion coefficient dependence as a function of pH and concentration of components was obtained in γ-globulin solutions by using photon correlation spectroscopy.

The clinical results of photodynamic therapy of maxillary sinusitis have been presented. 0.1%-Methylene Blue aqueous solution in combination with He-Ne laser irradiation (632.8 nm) has been used for treatment of patients with acute and chronic maxillary sinusitis. Efficacy of the photodynamic therapy was estimated with the use of the following criteria: the state of respiration, olfaction, duration of purulent discharge, reconstruction of transport function of ciliary epithelium, etc. The obtained results have shown that the photodynamic therapy is effective in comparison with conservative methods of treatment of the diseases.

Temperature is an intuitionistic indicator of laser and tissue thermal interaction. It can be used as verification of theory prediction as well as online clinic indicator. Temperature measuring is an indispensable tool in laser and tissue photo-thermal theory research. A computer-assistant noninvasive or minimally invasive temperature measuring system, which can be used in laser medicine, was introduced. Combined infrared radiation thermometer and miniature thermocouple, the surface irradiating point and inner temperature can be monitored synchronously. This system has some necessary advantages for in vivo tissue temperature measuring. The infrared radiation thermometer temperature range is 0~200°C and 1mV/°C analog voltage output signal can be tntered to computer. Inside LED red light and aiming sound can assure the distance between thermometer and measuring point to be the focus distance of 25mm and measuring circle has the least diameter of 2.5mm. The mini K-thermocouples were made by ourselves, their temperature range is 25~500°C, the diameter of 0.4mm, and the response time is rapid up to 0.1s. They are convenient for precision orientation in the organisms. Multichannel temperature measuring can reduce the measurement error and be able for distribution measuring. Integrated temperature sensor LM35 and numerical computation is used to compensate the cold port temperature of the thermocouples. The numerical computation can also revise the nonlinearity error with the least squares method quintic polynomial fitting, which excels to the circuit method. Calibration results with glycerin and mercury thermometer showed the absolute error value is less than 0.45°C within 26-98°C. The real time temperatures of murine skin tissue irradiated by CO₂ and Nd:YAG laser were measured. Such a system is suitable to high precision, large range, minute point, rapid response and real time tissue temperature measuring in laser applications. The saved data can be used for later analysis and compared with the thermal transferring theory model and calculation.

Basic clinical diagnosis principles are based on the application of neural networks embedded in the expert system of cerebral potential signal. Analysis of ordinary expert system, development condition and main property of neural networks is provided, in the meantime argumentation of recognition, acquisition, fundamental structure design and intelligent diagnosis is also available in order to explain the effectiveness and advancement of our method.

In this paper, simulations by Monte Carlo method are applied to reveal the effect of numerical aperture (NA) of a detector (backward registration) and scattering anisotropy of a sample (g) on the probing depth of the sample. Correlation between temporal and depth-resolved detection is investigated as a function of the considered characteristics, NA and g. Decrease of the numerical aperture of the detector or increase of the scattering anisotropy of the sample lead to probing of deeper depths and larger region around. These depths correspond to the maximal numbers of the detected photons measured with time-resolved registration. The better correlation comes from the use of fibers with smaller apertures and media with strong forwards scattering (high value of anisotropy factor).

Advances and key display applications are discussed. Computer, compact mobile, TV and collective large screen displays are mentioned. Flat panel displays step on CRT devices to leave them behind in 2007. Materials, active matricies and applications of bright radiative field emission and organic LED displays are developing successively and pressing other technologies to be used in photo-cameras, cellular phones, auto-cars and avionics. Progress in flexible screens can substantially extend the display design and application soon. 3D display systems are under intensive development, and laser is an important unit in some vaiants of holographic and volumetric 3D displays. Value forecast of different display markets is presented.

Molecular clusters are non covalent aggregates recognized as a new state of matter, whose properties are neither those of the gas-phase isolated partners nor those of their condensed phases. Molecular clusters have proved to be ideal systems for modeling molecular recognition phenomena, and their applications in many scientific fields interlocking the physical and life sciences are now well assessed. In the last few years, it has become possible, through the use of advanced laser techniques, to study the single interactions acting between individual components of a cluster without the influence of the solvent. The studies were carried out developing laser spectroscopic methodologies, capable of characterizing molecular clusters and probing the chemical bond breaking and forming on an extremely short time scale. This contribution deals with chiral recognition of molecules and clusters of biological interest in the gas phase through the application of the laser resolved mass spectrometric Resonant Two Photon Ionization technique (R2PI). The measurement of the spectroscopic shifts and of the fragmentation thresholds of diasteromeric clusters allows the determination of the nature of the interactions which control the formation of biological material and affect their stability and reactivity.

The coherent combining of two Nd:YVO₄ lasers has been demonstrated by use of a modified Michelson cavity. When the output power is 0.43W for the first channel laser, and 0.46W for the second channel laser, the combined output power of 0.83W is measured, which corresponded to a combining efficiency of more than 90%. When the output power is 0.89W for the first channel laser and 0.93W for the second channel laser at the maximum pump power, a combined output power of 1.6W is obtained. Moreover, the beam quality and coherent combining efficiency almost remain undecreased with the pump power. In addition, the environmental perturbations don't affect the beam quality and output power, and it has the potential for scaling to much higher output power by coherent combining of multiple lasers with this configuration.

We present an optically pumped vertical external cavity surface emitting laser using the semiconductor gain chip composed of quantum wells. With a semiconductor saturable absorber mirror (SESAM), we obtained a Q-switched-like pulse output. The output power reached more than 3 mW at a center wavelength of 1007nm whose repetition frequency was 100 kHz and time bandwidth was 500ns. We discussed the possible reasons that the output power was lower compared with the CW operation. We also investigated the relationship between the intra-cavity intensity and the output pulse width. By designing the gain chip more carefully and increasing the pump power, it should be possible to obtain entirely mode-locking operation.

The "Shenguang-II" Facility laser uses an 8-beam double-pass architecture capable of delivering several KJ of infrared or ultraviolet energy in a temporal pulse format of an approximately 1ns quasi-square. Ideally the output wavefront of each beam from the main spatial filter should be a plane wave. But a real output wavefront of the laser light beam with a 200 mm section diameter in our facility is always a complex superimposed one. On its cross section, it has a distribution of curvature radius, which is called "local curvature radius" here. But the quality level of the output wavefront is mainly marked by its "global curvature radius", which is an assessing result based on the local ones. To meet the requirements of enhancing the conversion efficiency of the KDP crystal, each beam of wavefront out of the main spatial filter should resemble a plane wave as possibly as it can. Because only in this way can we achieve an optimal match between the injection direction of the laser beam and the functioning angle of the KDP crystal. In other words, the global curvature radius of each beam wavefront should be as large as possible. We have assessed the global curvature radiuses of eight beams, wavefronts by measuring their local curvature radii using Hartmann method. Finally, we have acquired better frequency conversion efficiencies by correcting each output wavefront to a better level according to the measurement results.

Laser wavemeter with a Michelson interferometer is a high-precision instrument. The signal and data processing is so important to this wavemeter. It includes an optoelectronic conversion module, an amplifying and comparator circuit, a PLL unit, a counter, serial communications between the MCU and the computer. S1223 photodiodes are selected as the detectors. PLL unit including NE564 and 74LS193 is used to multiply frequency. The timing capacitor, loop gain coefficient, and the locking range of PLL are calculated. The counter is used to measure the number of interference fringes of the reference laser and the number of interference fringes of an unknown laser. Finally, the wavelength of an unknown laser is calculated and displayed on LCD. The signal and data processing of the wavemeter meets its accuracy of seven-bit significant figure.

The wavemeter can measure a wavelength of a tuned laser and an unknown laser. Due to the Doppler shift, the wavemeter operates and establishes coherent interference fringes on the detectors according to the Michelson interference principle. The movable reflector of the wavemeter is driven by a voice-coin motor. The closed-loop feedback design can ensure the movable reflector to move at a constant speed all the time. The electronic signals of both the reference laser and an unknown laser are multiplied in frequency by PLL (Phase-Locked Loop) unit so as to enhance the resolutions of the wavemeter. PLL unit consists of NE564 and 74LS193. Finally, the counter including a MCU (microcontroller unit), two 8254 programmable times, and a LCD calculates the wavelength of the unknown laser.

The two longitudinal modes whose polarizations are orthogonal to each other can appear in the resonant cavity of He-Ne laser cavity 140mm long with. The both modes compete each other. Controlling the resonant cavity length, the heater wrapped on it enhances the output power of the weakening mode so as to stabilize the frequencies of the both modes. The intracavity laser includes a laser resonant cavity, a heater, an analyzer, a polarized spectroscope, and two detectors. The voltage multiplying rectifier circuit is designed for the laser power. When the frequencies of the both modes are stable, the positive duty of the output pulse of the comparator is 50%. With the beat frequency method, the frequency stability of this laser is tested for 2x10^-10. The laser using this method has a lot of particular advantages that other methods do not possess, such as no piezocrystal or magnetic field.

The laser frequency noise is of crucial importance in coherent sensing applications. Indeed, the frequency noise of a laser has a direct influence on the lineshape and the linewidth, farther influence on the measuring accuracy. This topic is particularly interesting for laser diodes (LD), which optical properties make them key-devices for optical communications and Coherent Sensing systems. Phase noise in LD and the related problems that arise when such lasers are employed in coherent optical sensing systems are investigated. Applications to metrology and to new sensing schemes are described, experimental results are reported and the overall performances of the sensors are assessed.

Knowing the quantity of pollutants that the vehicle fleet is emitting to the air has become a vital question in almost every major city in China. Finding and fixing gross polluters is therefore very important to control the urban air quality and protect the human health and the environment. Remote sensing is an important advance in the technology of on-road vehicle emissions testing because it is fast, mobile, and unobtrusive. This on-road vehicle emissions remote system is designed to measure the carbon monoxide, carbon dioxide and opacity from the vehicles's tailpipe based on the Tuneable Diode Laser Absorption Spectroscopy (TDLAS). There are several advantages of this system such as compact design and ease of use. The measurement principle and optical layout of the instrument has been described in this paper. Field testing at Beijing and Hefei were conducted over one year, more than 6000 vehicles were tested. This vehicle emissions remote system has been shown to be able to measure CO,CO₂ and opacity from individual at highway speeds. In parallel, the plate license, speed, acceleration and length of vehicle are recognised by computer so that the owners of vehicles exceeding the permissible level of emissions can be identified.

The output performance characteristics of all-solid-state lasers end-pumped by a diode laser have been theoretically analyzed. Furthermore, the optic properties of laser crystals and nonlinear optical materials employed in all-solid-state lasers have been studied and compared by computer numerical simulation. The theoretical analysis and numerical simulation of optical parameters of laser-diode-end-pumped Nd:YVO₄ and Nd:YAG lasers were carried out on the basis of theory of crystal level structure and rate equation. The good output properties of high efficiency Nd:YVO₄ solid-state laser end-pumped by a diode laser are superior to of Nd:YAG compared in the same conditions. Therefore, Nd:YVO₄ crystal has been demonstrated as an ideal laser gain medium in solid-state lasers with account of its high laser gain and low pump threshold, etc. The conversion efficiency of 40% of Nd:YVO₄ crystal has been presented with an input pump power of 15W and a crystal length of 1mm. Furthermore, on the basis of phase-matching for the nonlinear optical crystal, the angular tuning curves of KTiOAsO₄ and RbTiOAsO₄ crystals for type-Ι and type-ΙΙ phase-matching have been simulated by computer, respectively. The tunable wavelengths of RbTiOAsO₄ crystal from 1.320μm to 5.484μm in type-Ι, from 1.324μm to 5.424μm in type-ΙΙ were both wider than that of KTiOAsO₄ crystal in the mid-infrared bandwidth. Therefore, RbTiOAsO₄ crystal is an excellent nonlinear optical crystal of which tuning range is wider than that of KTiOAsO₄ crystal in the mid-infrared band. As new crystals, the emerging of RTA and KTA has shown a promise for nonlinear frequency generation throughout the 1-5μm spectral region. Consequently, all-solid-state lasers capable of generating high quality near mid-infrared light have strong use value.

During the past few years, study of the all-solid-state blue laser has been focused on laser field applications in many fields and potential value of commerce. There has been much work done in order to obtain an efficient and simple solid-state blue laser source, this device being of interest for applications such as display technologies, production of high-density optical disk systems, high-resolution printing, or medical diagnostics. This paper discusses three means to realize all-solid-state blue lasers, including blue-emitting diode laser, direct frequency doubling of infrared laser diode (LD), diode-laser pumped all-solid-state blue lasers, respectively. However, direct emitters based on II - VI semiconductors are limited by the lifetime of laser diode. A practical and the most used way is the frequency-doubling of the 946-nm in Nd:YAG. In the field of nonlinear frequency conversion, we compare some different frequency-doubling crystals with improved optical characteristics, including higher nonlinear coefficient, wider transmission range, and more flexible phase-matching (PM) properties. Some nonlinear optical crystals usually used in solid-state laser are analyzed and compared, including KNbO₃, LBO, BBO, BiBO, CBO (CsB₃O₅), KBBF (KBe₂BO₃F₂). The recent progress on solid-state blue laser has resulted research in from gain media, frequency-doubled crystals, and configurations of the cavities. Two difficulties which are the coating techniques and the blue noise problem (the fluctuation of the laser output power) in the development of solid-state lasers are pointed out, and the techniques of solving blue noise problem that have been usually used in the past research are presented.

In this paper, we report a diode end pumped laser with a Yb³⁺-doped Ca₄GdO(BO₃)₃ crystal (Yb:GdCOB). The dopant concentration of the crystal was 7%. The crystal was pumped longitudinally at 976nm by a fiber-coupled diode laser. The maximum output power of the laser emitted at 1.055um was 430mW, and the laser slope efficiency was 75% with respect to the absorbed pump power. We also observed that the output power still increased when the crystal no longer absorbed more pumped power (the crystal had been saturated). The possible reason may be that the thermal lens effect changed the distribution of the laser mode. This will be discussed in part 3.

Based on the rate equation of four-level system and numerical simulation, the phase-matching characteristic of laser-diode-pumped Nd:GdVO₄/KBe₂BO₃F₂(KBBF) solid-state laser has been studied. The influences of pumping and oscillating spot size to output power and laser threshold with different gain medium are studied. Compared to CsLiB₆O₁₀ (CLBO) and β-BaB₂O₄ (BBO), the phase-matching characteristics of the nonlinear optical crystal KBBF are carried out through numerical simulation. For type I and type II phase-matching condition, KBBF which is more easy to realize ultraviolet laser output has shorter transmission bandwidth and broader tunable phase-matching angle than CLBO and BBO. It is useful to optimize and select the parameters of such systems.

Operating features of gain-guided Fabry-Perot (FP) laser diode (λ~1.55μm) in a continuous mode with integrated optical AWG-multiplexer as an external resonant cavity is investigated. The laser diode with antireflection coating (0.5%) facet and AWG-structure with external mirror as in-cavity frequency resonant selector is employed. The waveguide for AWG-structure was based on use of a silicon oxinitride (SiON) core and silicon oxide cladding layers with narrow mode (~5μm), size of AWG chip 10x10 mm, 1.55-μm band, 8x8 channels, wavelength channel spacing is 0.8 nm, crosstalk -25dB, the optical propagation losses ~3 dB. In the experiments we could achieve a narrow line generation corresponding to the AWG transmission spectrum. The lasing frequency was defined by switching of AWG-multiplexer channel. Furthermore, we have investigated the case of complex cavity build up of the FP laser diode with facets without coating and AWG-structure. In this case we have found the essential increase of Q-factor of the single line over FP laser diode cavity lines set. Actually, investigated laser cavities can be applied for creating the switched laser sources for WDM and ROADM networks, with requirements of narrow line width and switching between different wavelength lasing according ITU-grid.

The paper is based on the binocular vision sensor 3D measurement model, and a kind of low-cost single camera model used to measure coordinates in space is introduced. By using optic imaging dexterously, the single camera is imaged as two virtual cameras. Two parallax images which screened by the same object can be collected in the same CCD image surface. And then the 3D information of point can be retrieved. In this paper, the single camera sensor model has been constructed. This method overcame some disadvantages in double-camera systems, such as high system cost, reduce the measurement speed when switching the images of two cameras. This paper has also provided an economical, rapid, useful measurement approach. The experiment indicated the rationality and efficiency of this method.

Though controlling the coating reflectivity and intracavity diffraction loss, in the four cavity mirror configuration, a dual-wavelength continuous wave (cw) diode-side-pumped Nd:YAG laser that generates simultaneously at wavelengths of 1064 nm and 1319 nm is demonstrated. The relationship between power ratio of the two wavelengths and cavity length is studied. The cw dual-wavelength output power reaches 85 W when the average pump power is more than 500 W. The output power of respective wavelength exceeds 40 W, which is the best record as we know.

Silica spheres doped with Eu(TTFA)₃ and/or Sm(TTFA)₃ are successfully synthesized by using the modified Stober method (the base-catalyzed method). Transmission electron microscope (TEM) shows that the hybrid particles have spherical morphology and an average diameter of about 210 nm. Energy dispersive spectroscopy (EDS) confirms that the rare-earth (RE) complexes are incorporated into the hybrid spheres. The particles consist of 4-fold siloxane rings as determined by Fourier transform infrared spectroscopy (FTIR). For the samples doped with Eu(TTFA)₃ or Sm(TTFA)₃, the typical fluorescence spectra of Eu³⁺ or Sm³⁺ emissions are detected, respectively. However, for the samples co-doped with Eu(TTFA)₃ and Sm(TTFA)₃, photoluminescence (PL) shows the absence of Sm³⁺ emission and reveals the obvious energy transfer from Sm³⁺ ions to Eu³⁺ ions. Note that there are energy transfer processes between the ligands and Eu³⁺ or Sm³⁺. Therefore, multiple energy transfer processes are achieved within the hybrid spheres. These energy transfer processes maximize the possible fluorescence emission of Eu³⁺ ion. The lifetimes of the hybrid spheres are also measured. The RE complex/SiO₂ hybrid spheres described in this paper may find promising applications in optical devices and materials science.

The question of multiple photon and thermal excitation in low-dimensional nanostructures with deep holes, induced by x-radiation was considered. There are strong grounds for believing that observed thermally stimulated effective luminescence from x-irradiated porous Si (D.W. Cooke et al [1]) connected with generation by x-radiation of Dirac points in nanostructures.

Er-doped silicate thin films were deposited by the pulsed laser deposition technique, starting from an Er-doped silicate glass of composition: 65%SiO₂ - 3%Al₂O₃ - 11%Na₂O - 10%PbF₃ - 10%LaF₃ - 1%ErF₃. The irradiations were performed with an ArF excimer laser (pulse length ~ 30 ns) in a dynamic flow of oxygen at a pressure of 5 Pa. The laser fluence at the target surface was about 2 J/cm². The films were deposited on pure silica substrates, either at room temperature or heated to 200°C. The morphology of the films was studied by using optical microscopy, scanning electron microscopy and atomic force microscopy. The optical transmission of the films in the NIR-visible-UV regions (200-2500 nm) was recorded by using a double beam spectrophotometer. The optical spectra were analyzed by a computer code to evaluate the refraction index n and the extinction coefficient k along with the film thickness. The optical transmission was performed soon after the deposition and after one month to evaluate the aging effects. The films deposited at room temperature presented cracks over all the area of the film when submitted to SEM inspection or ion etching. Films deposited at 200°C remained undamaged. Optical waveguides were fabricated in the films deposited at 200°C by ion etching. Very low losses (down to 0.74 dB/cm) were measured by the prism coupling technique.

The uniform size distribution of nanometer materials is the crucial problem to achieve the high efficiency luminescence of silicon-based nanometer materials, but the nonuniform distribution of nanometer materials is the common problem in the preparation of silicon-based nanometer material. Using baffle and backscattering methods in the pulsed laser ablation (PLA), the nanometer silicon material with uniform size distribution was prepared. Big particles formed during the high energy pulsed laser ablation were well controlled. They were broken through collisions with the baffle, or deposited directly on the baffle. Using backscattered particles which are small atomic clusters, nanometer material is synthesized. It is smaller and more uniform in size distribution than conventional PLA. The photoluminescence (PL) characteristics of the material are improved than conventional PLA with higher intensity and narrower full width at half maximum (FWHM). The narrower full width at half maximum of the PL shows that the size distribution of the material is uniform. Otherwise the width would become wider because of the nonuniform size distribution. The unmoved PL peak of different areas on the material also shows the uniform size distribution. The blue shift of the PL peak from red wavelength to violet wavelength shows that the size of the material is smaller than nanometer materials deposited by conventional PLA. The size distribution optimized silicon-based nanometer material with improved PL characteristics, such as high intensity, narrow FWHM, would promote the realization of the full-silicon optoelectronic integration.

Tunable photonic bandgap fibers (PBGFs) were theoretically investigated by using the vector plane-wave expansion method and the vector finite element method. The tunable PBGFs are fabricated by filling high index material in the air holes of index-guiding photonic crystal fibers. The wavelength dependence of leaky loss and group velocity dispersion (GVD) has been illustrated. We show the leaky loss in the tunable PBGFs can be strongly depended on the refractive index of filled material due to the photonic bandgap effect. The tunable attenuator which operates at 1550nm is designed based on this PBGFs.

Based on a brief review on nanostractual ZnO, the talk will be focus on our recent researches on ZnO nanostructures and lasering actions. Controlling the growth conditions, various novel morphologies of nanostructural ZnO, such as nanodisks, aligned and symmetric whiskers and mirco/nanotubes have be fabricated by vapor-phase transport method based on vapor- liquid-solid mechanism. Amplified spontaneous emission and laser in UV range have been observed in some aligned arrays. The amplification and resonant behaviors will be analyzed in random, Fabry-Perot, and whispering gallery microcavities.

The objective of this paper is to find a method to design an active multichannel silicon microelectrode which is used to measure the neural signal. A circuit model when measuring the neural signal using the silicon microelectrode is proposed based on the structure and fabrication process of the microelectrode. The method of determining the dimensional parameters of the probe shank is discussed in the following three aspects: the structure of pallium and endocranium, efficient, coupled interconnects noise and strength characteristic of neural probe. The design criterion is to minimize the size of the neural probe and increase its stiffness to pierce the endocranium. The on-chip unity-gain bandpass amplifier has an overall gain of 40 over a bandwidth from 60Hz to 10 kHz; an input loadits resistance is designed to be above 30MΩ to guarantee a cutoff frequency below 100 Hz.

Stress distribution is one of the main factors influencing the reliability of MEMS (Micro Electro Mechanical System) structure. In most cases, MEMS devices work in motion state, the dynamic stress often affects the performances of the MEMS devices. For the first time, dynamic streses were measured by means of Raman spectroscopy and high-frequency modulation technology, the measurement result shows that dynamic stress at a certain point in silicon micro-resonator is in agreement with the analysis of theory.

Motion analysis of Micro-electro-mechanical system (MEMS) is a powerful diagnostic tool enabling evaluation of the dynamic behaviour and the status of MEMS. A backscattering differential laser Doppler system is presented. The working principle and optical diagram of the system are explained in detail. In accordance with the characteristic of the measurement system, high-performance phase-locked loop is used to detect a weak measurement signal. Then measurement signal is transferred to computer and further analyzed there. Furthermore, a laser focusing method is described to improve the measurement. The focusing system is composed of a spatial filter and an aspheric lens C240TM-A, and focal spot size is less than 50 um. The silicon micromachined resonator is used as an example in experiments, and the resonant frequencies and the mean amplitude of MEMS are determined. Experimental results indicate that dynamic characteristics of MEMS can be measured well.

The composite material of gold nanocrystals in porous glass matrix was obtained by chemical deposition. Optical spectra were fitted using Drude model. Real and imaginary parts of third-order nonlinear optical susceptibility were separately measured in surface plasmon resonance area using Z-scan technique and 20 ps 539 nm laser pulses. The obtained values of Reχ⁽³⁾ was -4.12±0.8×10^-8 esu and Imχ⁽³⁾ was -4.28±0.4×10^-7 esu. It was shown that the differences of absorption and refraction nonlinearities from field effect predictions can be satisfactorily explained by local field correction.

This report deals with the production and characteristics of Y₂O₃ -stabilized ZrO₂ (YSZ), A1₂O₃+YSZ, GDC, Nd:Y₂O₃ and Nd:YAG nanopowders prepared by evaporation of the materials with the help of a pulse-repetitive CO₂ laser. The design of a setup for the nanopowders production, scheme and characteristics of the original CO₂ laser excited by a pulse-periodic combined discharge are reported. For YSZ; Al₂O₃+YSZ, Nd:Y₂O₃, Nd:YAG the output rate was 15-25 g/h, for GDC ~ 50-75 g/hour, the energy consumption 30-40 (W*h)/g and 8-15 (W*h)/g, respectively. Data for the nanopowders specific surface, size distribution, the results of X-ray phase and structure analysis, as well as the results of luminescence analysis are discussed. The analysis of the obtained results showed that two main factors that determine the output rate of the nanopowders synthesis are the type of material evaporated and the mean laser radiation power. The mean size of the nanoparticles doesn't depend on the type of material.

A method for measuring the size, position, displacement and velocity of particles in a particle field with pulsed-laser holography is introduced. In-line holography and off-axis holography are applied to analysis of particle fields, especially off-axis holography. A 4-F optical system is used in the holographic recording system, in which the information on particles is recorded on a holographic plate. In a parallel optical field, the particle analysis can be performed with different instruments and in different depth of field. The parallel optical field imparts each particle with the same amplification ratio. This kind of optical system will favour the reconstruction, data processing, and calibration of particles in a particle field. An interference pattern of particles formed on a recording plate and relationship among diameters of the particles, far-field number, and the distance from the plate to a particle are analyzed. Some experimental results of the size, position, displacement, and velocity measurement of particles of a reconstructed particle field are presented. The particle identification and the formation of noise in an image of a reconstructed particle field in one section are also discussed.

Ranging performance is described for photoelectric equipment reconnaissance using an active laser detection system that is based on the 'cat's eyes' effect of optical windows. Active laser detection systems have an advantage over passive systems because they can measure target velocity and spatial coordinates. However, there are several challenging problems here because of the great distances involved, the low returned power of the uncooperative target, and the optical aberrations induced by the atmosphere. In the design of this system, the principle of detection is based on the 'cat's eyes' effect according to which the optical windows of photoelectric equipments have a strong reflect character towards incident laser beam. With 'cat's eyes' effect, the detection of uncooperative target can be translated into one of a cooperative target, so the ratio of returned laser can be increased. In this paper, the ranging performance presented here takes into account all the various elements of the system, from the laser emission, target, atmospheric propagation to the detector. The characteristics of back-reflected laser and an estimate of the laser Cross Section (LCS) from 'cat's eyes target' are investigated in theory and simulation. The Signal-to-Noise Ratio (SNR) is calculated by combining the probability of detection of the system for given electronic characteristics of the system and for a given probability of false alarms. On the basis of analysis of SNR, minimum detectable signal power, operating distance of the system and factors affecting the ranging performance is analyzed. Results indicate that system has characters of long range, and high sensitivity. It can be used to detect the aerial targets such as reconnaissance drone, navigate missile, reconnaissance satellite etc.

Initial stress would take place in transparent materials as glasses and polymers from casting, cementing or other processing ^[1][2]. Initial stress might cause cracks and ununiformity, which are not allowed particularly in some situations, such as glasses in lamp covers of the car, the recording media and transparent covers of planes' cabin ^[3]. It is very important to measure the initial stress in the transparent materials. In the paper, the wavelet method is applied to detect the initial stress of polymers, by which not only the initial stress would be tested but also the direction of the initial stress could be obtained simultaneously in the paper.

Being an industrial dye, the Sudan I may have a toxic effect after oral intake on the body, and has recently been shown to cause cancer in rats, mice and rabbits. Because China and some other countries have detected the Sudan I in samples of the hot chilli powder and the chilli products, it is necessary to study the characteristics of this dye. As one kind of molecule scattering spectroscopy, Raman spectroscopy is characterized by the frequency excursion caused by interactions of molecules and photons. The frequency excursion reflects the margin between certain two vibrational or rotational energy states, and shows the information of the molecule. Because Raman spectroscopy can provides quick, easy, reproducible, and non-destructive analysis, both qualitative and quantitative, with no sample preparation required, Raman spectroscopy has been a particularly promising technique for analyzing the characteristics and structures of molecules, especially organic ones. Now, it has a broad application in biological, chemical, environmental and industrial applications. This paper firstly introduces Sudan I dye and the Raman spectroscopy technology, and then describes its application to the Sudan I. Secondly, the fingerprint spectra of the Sudan I are respectively assigned and analyzed in detail. Finally, the conclusion that the Raman spectroscopy technology is a powerful tool to determine the Sudan I is drawn.

A new method of straightness measurement is developed in this paper. It makes interference beam be the reference axis in order to measure the straightness of rail or other objects under test. This method can reduce the measurement error brought by the thermal distortion of laser source and environmental factors in a certain extent, and the accuracy of straightness measurement is advanced.

This paper describes the necessity and the procedures for power calibration transfer at different laser wavelengths, and particularly in the range 9.2-10.8 μm where CO₂ lasers emit. To accomplish this purpose, the reference laser must be very well characterized, especially regarding its frequency and power instabilities. We have designed and built a line tunable, frequency and power stabilized sealed-off CO₂ laser operating in continuous wave and we have measured the operating parameters, such as tunability, frequency instability and power instability in different experimental conditions. The laser was optimized to work as a reliable reference instrument for power calibration transfer.

This paper presents the achievement of a China NSFC project. A technique to calibrate laser tracker using CMM has been developed. A laser tracker with working range of 35m can be calibrated accurately and quickly using a CMM with working range of 1m. Studies have shown that angular errors are the key contributor to measuring errors of laser tracker. A device to measure angular errors of laser tracker on CMM has been invented. Using this technique to calibrate the laser tracker on the CMM, the maximum measuring error of the laser tracker in measuring distance of 1.56m has been decreased sharply from 91μm to 28μm.

A three-dimensional surface mosaic technology based on global- coordination-measurement-systems is proposed in this paper. It overcomes the disadvantage of the most existing methods of multi-perspective mosaic having no control of the global error. With the high-resolution camera and several control points, a global coordinate system with high precision is set up using the camera self-calibration technology. Then, by introducing the control points pasted on the measured object, the translation between the global coordinate and the measured coordinate can be found out. The 3D data obtained from different viewpoints can be translated into a unique frame of reference. So the final results should be obtained. In theory, it can avoid the accumulative error. In practice, it is feasible to be tested in experiments.

A new initialization model for theodolite measuring system (TMS) is introduced in this paper. Errors from levelling and orientating which are main factors affecting the accuracy of TMS in short ranges, are eliminated using the new initialization model. The new method is investigated theoretically first, real measurements are then used to verify its validity and accuracy.

For volume contour visual measurement, multi measurement units and multi space images mosaic are needed to achieve the whole task. With the location information of pre-designed feature points, coordinate systems of multi-measurement units can be transformed and integrated conveniently and validly. So the identification and location of pre-designed feature points are the key technologies for space image mosaic and volume contour measurement. In this paper, an identification and location technology based on the invariable curve-moment and least-square ellipse fitting is proposed. The method can be used to identify and locate pre-designed targets with high precision automatically and has strong robustness. In the experiment, the location precision is less than 0.05 pixels and the fractional error of 3D space distance excels 0.56%.

A novel optical fiber displacement sensor is proposed and analyzed, which consists of a laser diode light source, an optical fiber probe, and three photodetectors. The bundling of optical fiber probe is sectioned into four parts: a centrally positioned fiber in the bundle for illumination, the first-neighbor circle of fibers for receiving (Group 1), the second circle of fibers for receiving (Group 2), and the remaining circle of fibers for receiving (Group 3). Then this paper describes the characteristic of the sensor compensation principle of three parts for receiving, mathematical model building and data acquisition system. The result confirms that the sensor can completely eliminate the influence of light source fluctuation, target surface reflectivity, and optical fiber loss. In addition, it can theoretically overcome the effect of inclined angle of the probe against target surface. The performance of the sensor using multi-grouped receiving fibers is improved and working distance is extended. Therefore, it can be more widely used, particularly in difficult measurement environments such as monitoring blade tip clearance and vibration of rotating turbo-machine.

The robot vision measure system based on stereovision is a very meaningful research realm within the engineering application. In this system, the industry robot is the movable carrier of the stereovision sensor, not only extending the work space of the sensor, but also reserving the characteristics of vision measure technology such as non-contact, quickness, etc. Controlling the pose of the robot in space, the stereovision sensor can arrive at the given point to collect the image signal of the given point one by one, and then obtain the 3D coordinate data after computing the image data. The method based on the technique of binocular stereovision sensor, which uses two transit instruments and one precision drone to carry out the whole calibration, is presented. At the same time, the measurement program of the robot and the computer was written in different program language. In the end, the system was tested carefully, and the feasibility was proved simultaneously.

Particle image velocimetry (PIV) is the newest entrant to the field of fluid flow measurement and provides instantaneous velocity fields over global domains. A monocular stereoscopic sensor is designed according to the characteristics of a 3D-PIV system. It includes only one CCD camera and two groups of symmetry mirrors. A measured particle in the flow field is mapped to the CCD image surface from two angular directions and each directed-picture occupies half the image surface. Imaging procedure is decomposed to illustrate the principle of the monocular stereoscopic sensor. It is proved that folding optical path enables the possibility of miniaturized sensor design. A perspective transformation model and a geometric error model are presented for analysis and design of stereoscopic PIV system. The relationship between sensor performance and its geometric parameters is discussed in detail. These parameters contain the angle between two mirrors in the same group, the angle and distance between mirrors in each group, the distance between mirrors and camera and so on. Enough theoretical research is made for the optimum design of the stereovision system. In addition, measuring accuracy is also related to the position of the particle, especially in both x and z direction. Simulation results indicate that out-of-plane errors are higher than in-plane errors in most area.

Displacement measurement is necessary in many different areas ranging from mechanical machining, building construction, land survey, ect. Displacement can be measured by traditional mechanical methods and optical means. Optical displacement measuring systems have the advantages of noncontact, high resolution, fast response, and more importantly being remote. We describe in this paper a laser-based displacement measuring system which can detect displacement or deflection of a remote object. The system consists of a laser source and a linear or area detector array. In order to achieve a long distance remote measurement, the laser beam is first collimated, and directed to the detector array which is attached to the object to be measured. The relative movement between the laser source and the detector will provide a measure to the displacement or deflection of the object. Novel signal and image processing algorithms have been developed to enhance the resolution and accuracy of the system. Techniques for long distance signal and data transmission have also been investigated. The design details of the system are described and experimental test results are presented. The features of the current displacement measuring system include high resolution and accuracy while still keeping a relatively simple structure and a low cost. The developed system will serve as a useful tool for many different engineering applications.

Cross-correlation algorithm is based on information theory and stochastic process theory. It has been widely used in many research fields, such as, medical ultrasound, ocean engineering, signal detection, modal parameters under ambient excitation, etc., but its applications in research of bubble curtains are seldom seen in domestic released periodicals, so our work is attempting to use cross-correlation algorithm. Through computing the velocity vector of bubble curtains, the bubble movement character can be known, i.e. the details of the bubble curtains can also be known. After comparing the differences between it and Doppler method, the cross-correlation algorithm has been applied to the measurement of bubble curtains parameters from a new aspect. The He-Ne laser and high-speed CCD camera are used to acquire the images of dancing bubbles, the velocities of bubbles are computed from image post-processed. Through improving conventional cross-correlation algorithm commonly used for analysis of flow field, the Fast Fourier Transform (FFT) has been used to implement the cross-correlation algorithm rapidly. In order to enhance the computing accuracy, Gaussian curve fitting is used to modify the correlation peak location and the fitting equations are listed, so the bubbles displacement with subpixel accuracy is obtained. Noises are stochastically added from hardware when acquiring images and the cross-correlation algorithm may also introduce errors. The character of velocity vectors result can be entirely wrong with ambient vectors, so they must be corrected. In order to calibrate the cross-correlation algorithm, images with universal displacement are used to validate its feasibility and reliability. The algorithm is applied to the computation of parameters in bubble curtains, yielding the vector graph of bubble motion. The algorithm is expected to be a valuable tool in acquiring the real-time velocity information in bubble curtains.

Temperature-independent micro-displacement measurement using a single fiber Bragg grating based on broadened reflection spectrum is proposed and experimentally demonstrated. The structure of specially designed bending cantilever beam (BCB) is proposed. The BCB induces axial strain gradient along the sensing FBG, resulting in a Bragg bandwidth modulation. The broadening of FBG spectrum bandwidth and the reflected optical power correspond to micro-displacement changes, insensitive to spatially uniform temperature variations. For a displacement variation of 20mm and a temperature change from 20°C to 100°C, the micro-displacement measurement deviation error is ±0.12mm without any temperature compensation. Through optical power detecting by a pin photodiode (PD), the micro-displacement sensor avoids complex demodulation process and potentially costs little.

The Model Yellow River is a physical model of the Yellow River in laboratory, the work of the terrain survey using traditional instrument is very hard and time-consuming. In recent years, the laser scanning for 3D surface shows the outstanding traits of speediness, precision and convenience. The measurement principles and processing system of the laser scan instrument for terrain survey were introduced in this paper, and a typical example indicated that the 3D laser scan system can obtain much precise information from the Model Yellow River. The laser scan data can be utilized in many research directions, such as river way movement and evolvement rule, silt-controlled, etc.

A new distributed optical fiber sensing technology to detect pipeline leakage in real time is introduced in this paper, which is based on Mach-Zehnder optical fiber interferometer. The principle of this technology is analyzed, and the phase change of light wave caused by the leakage acoustic wave is discussed as well. The results of the theory analysis and the experiments show that the measuring sensitivity of detecting leakage is greatly improved. Using this technology, the gas leakage of 0.4m³/min can be detected and the measured distance is about 50km under the condition that the pressure of the gas pipe is less than 0.2Mpa.

The industry welding robot can't real-time adjust its movement path according to the change in the position of the workpiece in a welding procedure, which affects the quality of welding a lot. The Real-time Visual Measuring and Tracking system acquires the three coordinates of the workpiece by visual measurement method, and navigates the robot to the correct position, consequently the welding quality improves. The system mainly includes micro structured-light visual sensors, a high-speed data processing unit, a display and setting unit, and protection equipments. From the experiment, it's shown that the system can measure the workpiece six times per second, and the precision of the measurement is better than 0.3mm. In a word, the system can effectively improve the robot welding quality.

Linearity measurement is the key problem in seamless steel pipe industry. For the modern industry of seamless steel pipe production, the traditional method cannot meet the needs of on-line and real-time measurement performance. Recently, visual inspection has developed rapidly and has the advantages of high speed, high precision, non-contact, automation and high manoeuvrability. So a novel approach to on-line and real-time linearity measurement of seamless steel pipe based on visual alignment technology is presented in this paper. Firstly the theory of visual alignment measuring is introduced. And then an on-line and real-time linearity measuring system, which consists of multistructured light sensor for seamless steel pipe factory of Tianjin, is invented with the technology of visual alignment. And key technologies for a visual alignment, such as the optimum design of high precision light-structured sensor, coordinates integration of multisensor, the mathematical model of visual measurement, and algorithm for ellipse center computations with high precision are studied in detail. Measurement results show that the measuring system is reasonable and can measure not only the linearity but also the coaxiality of large-scale parts.

In this paper, realized methods of distributed optical fiber sensing technique and a kind of sensing technique based on the Sagnac optical interferometer theory were summarized. The relationship between leakage position and phase difference (phase noise and receiving power) microbend loss is analyzed and simulated. We acquire that receiving power's increment will lead to phase noise's decrement. When faced with different wavelengths, phase noise differ. For the leakage position and phase difference,when wavelength is 1550nm, its resolving power can reach 0.148rad/m.

Laser-induced ultrasonic technology has been extensively studied and widely applied recently, for its advantages such as noncontract operation, nondestructive testing, broad bandwidth, high time, and space resolution, no shape limits on samples, etc. Firstly, the principles of laser ultrasonic generation and detection were introduced. Secondly, the application of the ultrasonic ratio method in measuring the surface defects was presented in detail. The experimental results were analyzed. Because the ratio method avoids measuring the velocity of the surface wave and reduces the experimental error, it is much more practical, reliable and effective in surface defect measurements.

The lidar-radar architecture has been developed and used in detection and identification of targets in many domains. Based on the single frequency monothilic NPRO (Nonplanar Ring Oscillator) and AOM (Acousto-Optical Modulator), a lidar-radar conceptive system for distance measurement has been constructed and investigated. The system consists of mainly three parts: the beat frequency laser source made up of NPRO and AOM, the transmitting and reflection collecting system and the lock-in amplifier signal processing unit. Then the distance measurement has been demonstrated using a 700-meter long single-mode fiber. In order to calculate unambiguously the actual distance, two synthetic frequencies have been introduced in turn. At last, using the lidar-radar setup, the displacement and velocity of a moving target which is mounted on a precise motorized optical bench have been displayed.

On the basis of the measuring principle of the dynamic active optical confocal probe based on time difference measurement that has a reference path, a dynamic active optical confocal probe based on time difference measurement but has no reference path is developed. In this paper, the working principle of this optical confocal probe is dissertated. A large-scale integrated measuring system is designed to simplify the structure of the probe and to enhance the stability of the probe. Single-chip microcomputer system with a high-speed ADC is selected in the measurement and control system of the probe. At the end of the paper, experiments on the performance of the optical confocal probe based on time difference measurement with no reference path are carried out. Experiment results show that the probe has a measuring resolution of 0.05μm, a measuring range of 0.2mm and a linearity of 0.4μm.

The retrieval of size and refractive index of a spherical nonabsorbing particle by angular dependence of scattered light in application to the scanning flow cytometry is considered We consider the range of angles available for measurement from 10° to 60°. For the problem solution the high-order neural networks are used. The retrieval errors were investigated at the ranges of the radius and relative refractive index 0.6 - 10.6 microns, and 1.02 - 1.38, respectively.