In this paper, based upon the general law oftransmission ofbasic model Gaussian beam, the reflection and refraction of laser at optical surfaces are analyzed respectively. Using the complex parameters of Gaussion beam, a simple algorithm for researching stray light and ghosts caused by Gaussian beam is presented. Depending on the algorithm, a dynamic data structure of tree which can describe the stray light of the system is built, an energy density superposition algorithm based on the distribution of complex amplitude of Gaussian beam is discussed, and a stray light and ghost analysis software for basic model Gaussian beam is developed. It can be seen from given example that the method describes completely the transmission of basic model Gaussian beam in optical systems and the ghost distribution. For given conditions (e.g. the maximum reflection times), the total energy density of Gaussian beam at certain position in optical systems with high accuracy could be calculated.

A temperature tuned cw doubly resonant optical parametric oscillator (DRO) consisting of a semi-monolithic KTP crystal and a concave mirror has been designed and built. Both critical and noncritical type 11 phase match KTP crystals are used separately. Under single-axial-mode pair operation, the output power combined signal and idler light fields up to 365mW were obtained at pump power of 680mW with critical phase match KTP. The output wavelength of the DRO can be temperature tuned over a range of 9nm around 1 064nm. Using non-critical phase matching KTP, the frequency tunable DRO was also realized in nondegeneration, the wavelength tuning is over 5nm around 1041nm and 1089nm, the quantum correlation between twin beams was also observed in whole tuning region. 2.8GHz continuous frequency tuning of the DRO was achieved in both case by tuning of the pump laser frequency. The pump laser was homemade all-solid-state intracavity frequency doubled and stabilized YVO4 laser at 532nm.

In this paper, according to theory of thermal elastoplastic and phase transformation, combined with characteristic of laser quenching, the effect of cooling velocity on temperature field and phase contents is analyzed, mathematical model of transformation during laser quenching and nonlinear heat conduction equation is presented. The computer simulation oftemperature field and distribution of volume in hardening depth after laser quenching are proposed. Also, after laser quenching experiment of 40Cr steel under case of controlling boundary condition, it can be shown that theoretic calculation fits to experimental result, and a new feasible approach is provided to improve the high-toughness of metallic material.

This paper describes a new approach for flattening high-power and high-gain CO2 lasers. A periodic change of curvature of concave mirror causes beam modes to jump in the course of time. Averaging out these beams results in an intensity profile with good uniformity. It is also compared to the output intensity ofthe resonator without vibration.

In this paper, the fiber laser with D-shaped inner cladding fiber is presented. The fiber laser has a second mirror which configuration is called two-mirror cavity to provide different feedback and to stabilize the output. The dynamics with different feedback 4%, 40%, 70% and 90%etc. are studied. In experiment, it obtained 2.32W output with 4% Fresnel reflection of the fiber. With different feedbacks it founds three thresholds, Pth is the laser threshold, pthB is for SBS (stimulated Brillouin scattering) in the fiber laser, and is for SRS (stimulated Raman scattering). The higher feedback level is, the lower threshold is. Also the PthB dynamics appear different characters with the increase of pump power. Under certain condition, the output is stable ns pulses. The pulses width has relationship with the feedback from the second mirror. The phenomena are analyzed quantitatively.

In this paper, we develop a quasi-cw InGaAs microlens-free diode arrays side-pumped Yb:YAG slab laser which operates at 25Hz. The pump light is transmitted by a lensduct which transmission efficiency is measured about 80%. The laser cavity is plane-concave. We have achieved l6mJ output energy using 8mm X 3mm X 1mm dimension and 5at.% Yb doped crystal with 345mJ input energy of diode arrays which operate in ims pulse mode. For another 8mm X 3mm X 2mm(5at.%) crystal, 8.7mJ output energy is obtained; the beam quality factor M2 values are measured to be 5.83 and 7.66 in the vertical and horizontal directions respectively. The water temperature for cooling diode arrays and crystal are 11.8 ° C and 5 ° C separately.

In this paper, we main to optimize the micro channel heat sink structure parameters through simulating calculation approaches based on the analysis of the thermal characteristics. We also find the relation between the thermal resistance and the width of channels and fins of the micro channel heat sink. What's more, the effect of cooling liquid pressure drop and depth of channel on thermal resistance are given. We obtain the lowest thermal resistance at t=200 ?m,wc=160 ?m, wf=320 ?m.

The fiber laser's excellent focus and efficiency, small size and light weight makes it highly promising not only for telecommunication, but also for industry and medical applications. In a double clad fiber laser, the inner cladding for guiding the pump light is provided around a core doped with active ion (e.g. YB3+, Nd3+, Er3+, etc.). The recent progress of fiber laser is reviewed at first in this paper. Different shapes of inner cladding are investigated to increase the pumping efficiency. Beam-shaping optics deliver high-power beams as the pumping source is discussed. Finally, a 4.9W cw double-clad fiber laser demonstration experiment in SIOM is described.

Compact and efficient blue light source are attractive for numerous and technical applications such as laser-based metrology, data storage, medicine, xerography, and biotechnology. Nonlinear frequency conversion remains an attractive route to achieving blue light sources. In this paper we show that 915nm laser diode pumped Yb-doped double clad fiber lasers (YDCFL) can provide efficient 978nm light. Frequency doubling ofthe 978nm line ofYDCFL can else generate blue (489nm) light. We setup theoretical model of Yb-doped double clad blue fiber laser. The threshold and Output powers at 978nm and 489nm versus the fiber length, the core diameter, the size and numerical aperture (NA) of the inner cladding, and pumped power are studied through theoretical simulation. The optimum parameters are obtained. In the design of three-level double-clad fiber lasers, we consider two main considerations: high pump brightness and an optimum balance between spectral filtering and modal gain discrimination. Atype I phase—matched BBO crystal is used to generate second harmonic light(489nm).

The generation of the third harmonic for quasi-continuous laser diode(QCWLD) pumped Nd:YAG laser are studied. We compute numerically relations between light wavelength and phase-match angle, and effective nonlinear coefficient, and walk-off angle for third harmonic generation (THG) in BBO crystal. Frequency tripling experiment is done using electric-optic and acoustic-optic Q-switching Nd:YAG laser pumped by high power QCWLD. We use type II KTP crystal to generate the second harmonic(532nm) , and type I BBO crystal to generate third harmonic (355nm). Inner cavity frequency and out-cavity tripling are done. Maximum pulse energy of 1 .5mJ for 355nm is achieved.

In the modern weapon systems, more and more the TV tracking systems have been widely used. It has more good characteristics than infrared tracking, laser tracking, radar tracking. When the high-power or high-energy laser irradiates the CCD video camera, it will be disturbed or damaged and lead to the TV tracking system damage, such as losing the tracking target. In the paper, the laser damage ofthe CCD has been studied theoretically and experimentally.

A new mirror cooled by organic phase change material is presented in this paper. In virtue of the finite element analysis software—ANSYS, the transient numerical simulation on deformation of mirror surface in 10 seconds during laser working time is presented in the paper, which is based on heat transfer and thermal-elastic laws. The curves of temperature and thermal deformation along the radium are provided in the case of uniform beam and Gassian beam respectively. The result is showing that the passive cooling method with organic phase change materials to reduce thermal distortion on mirror surface is a g*ood way and small deformation can be achieved to a satisfied extent.

There are four kinds of reflectors: 1, flat mirror; 2, common retroreflectors; 3, phase conjugate mirror (PCM) and 4, the fourth one. "Corner cube" belongs to 2. However, if the dihedral angle lines and their images of the corner cube are taken into account, it is recognized as super-conjugator. The terminal mirror of laser cavity is replaced by such an element, it has ability to compensate distortions inside the cavity and misalignments insensitive and has being rapidly used. How to perform nonlinear phenomena by a well known linear element? Here we show the essentials by way of special array concept.

In this paper, the periodic all dielectric multilayers of high reflection phase retarders are designed. And the software of Tfcalc has been used to optimized for the design that produces a 900phase shift between the p- and s- polarization components at the incidence angle of 540 and at the wavelength of 1315 nm while maintaining high reflectivity (>99.90%) for both components. A tolerance analysis indicates that the coating layers must be deposited within ±14% to achieve a 90± iO° phase shift error.

For gas laser, working gases in resonator have two interaction with laser. One is to generate excited radiation, the other is to affect the propagation of the laser beam. For the latter, gas thermal lens has great effect on laser beam in the resonator for high-power CO2 laser because of long resonator and high laser power in resonator. In this paper, a physical model for gas thermal lens is proposed. As well as the influence of thermal lens upon the propagation of the laser beam in the resonator according to this model is analyzed. It is found that gas thermal lens will transform the laser beam acting as a negative lens which is at the middle of the resonator since the symmetry of the resonator. This negative lens will transform the beam waist position and radius to deviate the idea beam waist position and radius which are determined by the passive resonator. And this deviation causes the mismatch of the transformed laser beam with the resonator. Further more this mismatch results in the energy couple of TEM00 beams to the higher ones to form the mix-mode laser beam and decreasing laser beam quality. In the paper the effects of the laser power, on laser beam modes are analyzed. And as an example, the laser output mode of a high-power CO2 laser with radio-frequency excited and fast-axis-gas-flow is calculated from the above theory. Meanwhile, the output mode of this type of laser is measured by high-power laser beam analyzer - laserscope UFF100. And the calculation is accord with the measurement. So for high-power C02 laser, the gas thermal lens is an important reason which influence the output mode ofthe laser beam.

We have describe a simple diode-side-pumped high-power and high efficiency Nd:YAG laser that produces 240 W of power continuous-wave(CW) with 33% optical-optical efficiency. We used the technology of diode laser close-couple to realize high pumping efficiency ,We measured the thermal lensing focal length to design the laser resonator, which decrease the rod thermal effect. By changing the resonator parameters ,we can adjust the fundamental mode size and the output beam quality.

A high power intracavity frequency doubled Nd:YAG laser with KTP crystal and A-O Q-switcher pumped by 1600 Watt-808 nm laser diodes and its thermal effect are discussed. Also we proved that the title angle of KTP crystal can be to compensate for the phase mismatching and to solve the problem of the drop of green laser output power along with the increasing temperature of KTP crystal. Then based on optical parametric oscillator (KTP-OPO) pumped by 532 nm laser and their frequency doubling (with KTP and BBO) a Watt-level red and blue laser system which would be provided as RGB laser projection display are described.

As well-known fact, the relation between the radius of TM00 mode of solid laser and 1/ft (the focal power of crystal) can be expressed with double U curves'1. In this paper, self-Q-switched of Nd:YVO4 solid laser of asymmetry flat-flat cavity was studied theoretically and experimentally, using this character. Self-Q-switched giant pulses with 200ns (FWHM) were observed in experiment. Pumped pulse width was 100µs. Peak power of laser pulse was several million times than the CW level. The experiment results were in good agreement with the theory. Giving the result of experiment, we offered a method to enhance the peak power of pulse.

The research, on the damage mechanism to the high-space target by the ground laser, aims to determine the saturation or damage threshold of optic-electro sensors on the target. The laser beam to the target is relationship with the following features: The speediness of the energy accumulation and the laser tracking stability in long distance. The speediness needs high peak-power in the shortest time, while the stability needs high speed-precision ability to the servo system on earth. Obviously, the pulse laser is more effective than the continuous laser when considering the speediness. Here for the 10.6 ? m CO2 laser, the interfering effects are dealt with to the target in 500km space. Provided that the turbulent air does not influence the laser beam, the power of periodic rectangle-pulse laser arriving on the space object is evaluated first. Then the laser staring time on the object is calculated. Third, the laser energy accumulation on the space object is analyzed, and last the saturation or damage threshold ofthe object is determined.

In this study, high efficient backward Raman compression has been achieved by a 10J KrF pump laser from Heaven-1 MOPA system using focused-beam geometry. A preliminary stage of experiments was carried out in CIAE with main results reported here. Up to 1.7J of first backward Stokes(268nm) output with pulse duration of 1.5ns was obtained as the pump (248nm) laser was 1OJ of energy and 22ns of pulse duration. The pulse duration is compressed by 15 times with total energy conversion efficiency up to 17%. The high conversion efficiency of backward SRS is considered mainly attributing to the focused geometry. The mechanisms of backward Stokes pulse self-shortening and forward-backward gain asymmetry compensating have been discussed. The backward Stokes pulse duration is considered to be much less than it was observed using a relatively lower bandwidth oscillograph. Further experimental research on precision time measurement will be performed later this year.

During design and experiments, multi-diode-laser -module was employed to pump a double AO switched Quasi-CW YAG laser with KTP or LBO crystal as frequency doubler. Thermal lensing effect in laser rod and frequency doubling crystal were both considered. Cavity design with ABCD law and crystal thermal compensation given in detail by numerical calculation. High average power output was achieved.

Self-pumped phase conjugation in Ce-doped barium titanate crystal is investigated with 1-Hz-repetition-rate nanosecond pulses from a Q-switched frequency-doubled Nd:YAG laser (532 nm wavelength). Phase conjugate reflectivity as high as 21.5% are obtained at an incident angle of 500. Dark storage time, defined as the time after which the phase conjugate reflectivity declines to 90% of steady-state value when photorefractive crystal is in dark condition, is more than 20 minutes. Furthermore, self-pulsation of SPPC energy is studied.

An integrated DOE is designed for beam combination and shaping. The DOE is double-faced carved. One is transmission blazed grating to convert four declined incident incoherent beams to parallel beams, the other is continuous profile relief for shaping. The simulated intensity focal-plane profile has little modulation in the main lobe and high diffraction efficiency.

High-power CO2 laser beam intensity distribution is nonuniform, which is caused by inhomogeneously gain medium. Aiming at that nonuniform distribution, a new resonator consisting of a roof mirror is designed. At the same time the beam intensity distribution is modified to obtain greater temporal uniformity by reflector's periodically vibrating. Output modes of both the resonator with a pair of parallel-plane mirrors and the former new resonator are obtained by numerical simulation calculation with Fox-Li iteration. Simulated results are presented that with the resonator uniformization ofthe beam intensity distribution can be achieved.

In this paper, We have proposed a new cross section shape of inner cladding benefited from the conception of unsteady cavity in laser technology. The absorption characteristic of this new type double-clad fiber is analyzed in detail with ray tracing method. For this new type and rectangular double-clad fibers, with core diameter 8im and pump area 100?mX 100?m, about 98% pumped propagation rays are absorbable after 100 times reflection in the inner cladding, so it is possible to achieve very high absorption efficiency. However, for circular, offset and D shape double-clad fibers, with same core diameter and pump area above, only 10%, 50%,80% pumped propagation rays are absorbable.

Second harmonic generation from 858nm to 429nm has been investigated at room temperature by using Potassium Niobate (KNbO3) crystal. The optimum parameters for nonlinear conversion in our designing singly resonant, external ring cavity pumped by the Ti: Sapphire laser are established. In addition, we investigate the conversion efficiency over a range of operating conditions. When the cavity is scanned, 170 mW (235mW corrected for losses of the output mirrors) of blue light at 429nm is produced with 600mW of pump power near 858 nm whereas 137 mW is generated with 565 mW of pump when the cavity is locked.

The free-vortex aerodynamic windows (abbr. FADW) can take the place of the conventional solid windows for high energy lasers to solve the problems caused by the intrinsic fractional absorption of the laser energy. Usually the procedure in designing FADW includes two central processes. The first is to design the asymmetric supersonic laval nozzle using the method of characteristics and the method of simple wave under the ideal conditions, and the second is to design the diffuser. The method of designing the diffuser of FADW is based on the experimental method mostly, but the diffuser's properties influences the performance ofthe overall FADW system deadly, so an experimental prototype of FADW whose structure and layout is adjustable has been designed and manufactured to optimize the design of the diffuser for FADW system. This paper reports the design methods of the FADW system and discusses the experimental results. The results show that this prototype of the FADW has good running properties, and FADW whose structure and layout is adjustable can be used to optimize the FADW design perfectly.

A high-power-output single-frequency Nd: YVO4 infrared laser has been designed and built. The thermal focus length is distinct and sensitivity in case of coherent pumping with high power and is considered in cavity design. A stable ring cavity was important for the laser output frequency tuning. Under single frequency operation, the maximum output power of 3.9w is obtained at 1064nm with the LD pumping power of 16 W. Over 1 GHz continuous frequency tuning was obtained when the cavity length was scanned by PZT. The cavity stability was also analyzed.

Under 400~800W/cm2 1315?m CW laser irradiations, the distortion of multi-layered dielectric coatings deposited on silicon crystal and/or fused silica substrates is tested by a Shack-Hartmann wave-front technique. Take account of the influence of environmental noises and air convections, the thermal absorption of the coatings is assessed from the CW thermal conduction equations and the thermo-elastic equations.

A new gain saturation model of chemical oxygen-iodine laser (COIL) is deduced from the conservational equations of population number of upper and lower lasing levels. The present model is compared with both the Voigt profile function (VPF) model and its low-pressure limit model, and the differences between different models are pointed out. These differences are ofuse to the optimization of COILs' adjustable parameters.

The increasing capacity of wavelength-division multiplexing (WDM) transmission systems requires higher output power of erbium doped fiber amplifiers (EDFAs). The two improvements are the use of double cladding fibers (DCF) and the addition of ytterbium oxide as co-dopant in the glass base. In this paper, the operation principles of double-cladding erbium-ytterbium co-doped fiber amplifiers were analyzed. Numerical analysis of erbium-ytterbium co-doped DCF amplifiers using EY801 fiber manufactured by INO, Canada has been performed based on the rate and propagation equations. The maximum output power as functions of the fiber length, the input pump power, the erbium-ytterbium concentration and pumping ways were described. The results show that the ideal erbium-ytterbium co-doped DCF amplifier with EY801 fiber is that with the fiber length of about 62 meters, with as higher as possible pumping powers, and with doubled-ended pumping configuration.

? phase-shifted distributed feedback fiber lasers , ofwhich the power would focus on the phase-shift region ifthe coupling coefficient was high enough, was often adopted in order to acquire single-frequency output. But if the phase shift region was far away from the center of the grating, the output wavelength would be different that the fundamental mode would focus on the port which was near the phase shift region while the ±1 modes would focus on the other port due to the spatial hole burning. Both the theoretical analysis and experiments were presented.

Second harmonic generation of tunable TEA CO2 laser has the greatest potential for providing the coherent radiation in the wave range of 3~5µm which has many virtues. But the low conversion efficiency has restricted its wide application. In order to raise the conversion efficiency by lengthening the nonlinear effecting extent, two crystals were used which were placed in symmetrical position. In this way the beam can be compressed at the same time. In our experiment, the conversion efficiency up to I .5 times that of one crystal was achieved. Another factor that can affect the conversion efficiency was the quality of the pumping laser, so a plasma shutter was used to shape the laser pulse. Through the shutter the pulse energy was decreased but the pulse width was compressed accordingly, so the pump power was enhanced. By means of this, the conversion efficiency was improved from less than 2% to 12.9% and the highest output energy of 1 .44mJ has been achieved.

Two kinds of Q-switched RF excited waveguide CO2 lasers using Q-switching and FM crystal respectively are studied. They are used to detect laser return signal from targets of 20m distances without using telescope in experiment. The waveform of pulse laser heterodyne and its frequency spectrum of Fourier transform scattered from targets are studied. According to radar distance equation, the laser can be applied to detect targets of 5Km distances using telescope.

Laser-induced breakdown spectra (LIBS) produced in ambient air and pure gases with tightly focused, micro Joule, femtosecond Ti:sapphire laser pulses have been studied experimentally. The breakdown region typically measures around 10 µm in diameter and 120 µm in length. Both line spectrum and blue-shifted continuum spectrum are recorded for air, N2, O2, Ar, Kr, and Xe when the optical intensity reaches 1014W/cm2, using 40 fs pulses. It is also found that the profile of the continuum varies only slightly for different gases. For a given gas the continuum profile changes along different positions of the narrow micro plasma track. In particular, the blue-shifted continuum is stronger at the initial position of the plasma track (closer to the focal lens), whereas the line spectrum is more dominant when light collection is made at the further end of the plasma track. Unlike the results reported by others for longer pulses, higher energy and also larger plasma zone, the majority of line spectrum we obtained is found around 800 nm, the central wavelength ofthe input Ti:sapphire pulses.

In our experiment, the continuum, which is from 200nm to 300nm and centers at 240nm, is obtained by electron beam pumping argon. With the rear mirror, its small signal gain has been measured. Base on the experimental results, the resonator effects are observed at 240nm. When the resonator is formed, the intensity near 240nm increases more than 10 times. In the theory, the kinetic model on electron beam pumping argon is analyzed. The maximum number density of Ar2+ is 1.142x1015cm3. Based on the number density, the optical gain coefficient is very small, 0.025cm-1. These theoretical results are verified by the measurement of small signal gain coefficients and resonator effects.

Using a slab shaped laser media can effectively reduce thermally induced strain and aberration. In this paper we report the experimental results obtained using an end pumped Nd:YVO4 slab laser with a hybrid resonator. With this design we measured 110W output with the beam quality of 1.3 and 1.5 in two orthonormal directions.

An efficient second harmonic generation of diode end-pumped electro-optical q-switched Nd:YVO4 slab laser is demonstrated. A maximum output power of 15.6W at 532nm was obtained at a repetition rate of 40kHz, the corresponding conversion efficiency was 60% and the pulse width was 11.3ns. At a repetition rate of 10kHz, the pulse energy of 532nm was 1.2mJ and the pulse width was as short as 5ns. The beam quality was M2 < 1,3.

We describe the demonstration of the high pulse energy and high efficiency second-harmonic generation (SHG) at 532-nm using large aperture CsLiB6O10 (CLBO) crystals for the first time to our knowledge. A pulsed green energy of 25 J has been generated with 34 J of input 1064-nm Nd:glass laser radiation using a two-stage crystal architecture. High conversion efficiency of 74% has been attained at fundamental laser intensity of only 370MW/cm2. This result represents the highest green pulse energy ever reported using the CLBO crystals. We discuss in detail the design and performance of SHG using CLBO crystals.

The most recent development in industrial fabrication processes of low temperature poly-silicon by means of excimer laser and optics system is presented: . The recently developed high performance excimer laser, which delivers the highest output power currently commercially available in combination with two different beam shaping methods, the commonly known ELA-technique and the new SLS-technique for enhanced Field effect mobiliiy in the LTPS, is demonstrated.

In this report, polycrystalline Yb:Y 2O3 ceramic laser has been demonstrated for the first time. With a pump power of 11 W at 937 nm, 0.75 W cw laser output at 1078 nm was obtained. The laser had a threshold of 4.7 W and a slope efficiency of 12.6% when an output coupler of R = 98% was used.

A new type of MeV ion generation at laser-plasma interaction has been measured based on the observation [1] that ps neodymium glass laser pulses of about TW and higher power do not produce the relativistic self-focusing based very high ion energies but more than 50 times lower energies. On top the strange observation was reported [fl that the number of the emitted fast ions did not change at variation of the laser focus intensity by a factor 30. This can be explained by the effect that without an inadiating prepulse, a pui plane gcmetnc skin layer interaction mechathsm occurs [2]. Neither relativistic self-focusing is possible nor the process of thermalization of quiver energy by quantum modified collisions. Following our conclusions about the difficulties for the fast ignitor concept of laser fi.ision [3], we can explain how these mechanisms can be used for studying the self-sustained fusion combustion waves [4] as known from the spark ignition at laser fusion. We further expect an improvement of the conditions for the experiments [5]with the highest laser fusion gains ever reported where even no pre-compression of the ftision plasma was necessary.

This paper presents the process and methodology employed to perform evaluation and analyses for the optical interface that delivers and receives 10Gb/s Ethernet traffic on Cisco’s industrial leading switching architecture. Especially, we examined in detail the optical properties for commercially available 10GBASE-LR transceiver modules, with respect to IEEE 802.3ae specifications. The sampled results under room temperature are listed for comparison. Eye diagrams were recorded as a function of transmission distance, as well as temperature variation. System stability issues are also studied following a brief introduction to Cisco standard ODVT (Optical Design Verification Test) procedure.

The analytical formulas of laser threshold of the quasi-four-energy-level system for Tm3+,Tb3+:LiYF4 are deduced from rate-equation of transition. The energy transfer between Tm3 and Tb3 is discussed. The optimal concentration of Tm3+ and Tb3+ and the optimal length of the crystal rod for the minimum threshold pump intensity are calculated. It shows that when Tm3+-ion-doped concentration is comparatively high the threshold of the~1.5?m laser corresponding to 3H4 ?3F4 transition of Tm3+ increases because of the cross-relaxation. When co-doped with Tb3+ ion, on one hand, the threshold tends to decreases by contribution of Tm-Tb energy transfer which effectively reducing the population on the terminal laser level, on the other hand, it results in an increase in threshold due to Tm-Tb energy transfer which also reduces the lifetime of the initial laser level. In this paper the theoretical analysis for optimal Tb3+ concentration is fumished. Calculation shows that for LiYF4 crystal with the Tm3+ concentration being 1atm% the optimal concentration of Tb3+ is 0.2atm%. In addition, the dependence of optimal length of the crystal rod on the concentration of Tm3+ and Tb3+ and distributed rod loss were analyzed.

Two types of plasma shutters which can achieve pulse shaping of transversely excited atmospheric-pressure (TEA) CO2 laser are presented. We have designed two optical devices, which are plasma shutter and laser triggering spark gas (LTSG). The pulse forming network circuit used for precise triggering control is designed. In experiment, optical triggering gas free-breakdown plasma shutter and electrical triggering plasma shutter controlled via LTSG are researched for pulse shaping of the TEA CO2 laser. The collimated laser beam is focused at the center of two ZnSe lenses, producing an intensity of approximately 7x 1O'°W/cm2. In order to optimize truncated laser pulses, some operating parameters which include gas types filled in plasma shutter, gas pressure, LTSG 's voltage, and so on, are investigated via experiments. Using this technique, the nitrogen "tail" of the TEA CO2 laser pulse can be clipped, thus shortening the output laser pulse from the duration ~60ns to ~30ns.

Stabilities of output power and frequency of monolithic semi-nonpianar ring lasers are investigated in experiment. Fluctuation in output power is less than +-0. 1 % with output power 1 .5W over a period of 3 hours. In free running, the root Allan variance of beat frequency between two monolithic lasers is lx 10-10 for averaging time is. Slow frequency drift is less than 10 MHz over a period of 1 hour.

A YAG super short pulse laser (355nm, 35ps) is used as an exposure source. The electron action in imaging process is directly related to photographic efficiency of silver halide emulsion. Photoelectrons generated under actinic illumination of photographic silver halide systems occur in free, shallow-trapped and deep-trapped states. Different state of electrons has different influence on the dielectric function of silver halide material. The contributions of free and shallow-trapped electrons to the real and the imaginary part of the dielectric function are different by some orders of magnitude. The lifetime of different kinds of electrons can describe these complex processes and the lifetimes of free and shallow-trapped electrons can also reflect the sensitivity and other efficiency of silver halide emulsion. Microwave Absorption and Dielectric Spectrum Detection Technology is a powerful tool that could quickly detect the change of dielectric function of emulsion film. The lifetime and decay curve of the free photoelectrons and shallow trapped electrons of different emulsion samples have been measured and analyzed.

Dual-wavelength operation of an actively mode-locked fiber ring laser generating picosecond pulses was demonstrated by using a cascaded sequence of two fiber Bragg gratings in the laser cavity. By adjusting the distances between the two fiber gratings, simultaneously mode-locked operation of dual-wavelength at different repetition rate could be achieved when the modulation frequency was appropriate. In the experiments, dual-wavelength pulses at about 2GHz latorand 4GHz (when the modulation frequency was about 2GHz) or at about 2.5GHz and 7.5GHz (when the modulation frequency was about 2.5GHz) were simultaneously obtained and each wavelength could be tuned in arrange ofabout 5nm.

A diode pumped Nd:YLF regenerative amplifier is developed, which works at wavelength of 1053nm and repetition rates of 1Hz. It can produce laser pulses of 2mJ energy, 4ns width in the base transverse mode TEM00. Total gain of 1x107 is reached, and pulse-to-pulse energy fluctuation doesn't exceed ±4.7% Experimental setup and detailed results are presented.

A novel method is investigated for compensating deflection in a spatial-temporal transform pulse shaping system: using optical fiber instead of a second electrooptic deflector. By changing the width and shape of filter, pulse duration ranging from 740ps to 4.5ns is observed, and the mode quality of output beam is good. This novel method has relaxed requirements on electrooptic deflector and simplified the whole system.

Chirped pulse amplification(CPA) has become a common technique for the generation of ultrashort and high peak power femtosecond(fs) optical pulses. One key point of this technique is the reasonable design for the pulse stretcher. We improved the aberration—free stretcher replacing the two spherical mirrors with two concentric rectangular focused cylindrical ones. The first mirror is convex, and the second one concave. Their radius of curvature ratio is two and of opposite sign. This combination cancels spherical aberration and astigmatism, and has no on-axis coma and exhibits no chromatic aberration. We calculated the group velocity dispersion(GVD) of the stretcher by ray-tracing model. Supposing that the distance between the grating and the center of curvature is a variable 1, we obtained the variety of the group delay and the GVD of the stretcher with the parameter 1 and the incidence wavelength A .For the input pulse, let pulsewidth to 9.8fs , the initial chirp C=O.75, the distance l=O.lm, we gained GVD was 2.5fs2/jm for the center wavelength 790nm, the stretching factor was 90197.4, that is, the seed pulse(9.8fs in duration) can be stretched to 884 PS

This paper introduces a new data communication way. That is to realize data information modulation and demodulation in traditional CO2 laser sending and receiving process by installing a substance called photoelectric crystal. It stresses selection of photoelectric crystal and major design specifications of laser modulator and demodulator. Comparing with other ways, the one demonstrated in this paper makes it clear that as standard data communication interface whose transmission medium is CO2 laser, it owns greater value in application.

A YAG super short pulse laser (355nm, 35ps) is used as an exposure source. The free photoelectron lifetime and decay process of silver halide crystals could be measured and analyzed by the microwave dielectric spectrum detection equipment (MWA). This is a powerful tool that could quickly detect the change of dielectric function of AgX microcrystal. This technology enables measurement of the free photoelectron and shallow trapped electron decay process simultaneously that decide the sensitivity and other efficiency of silver halide material.

Two-photon laser-induced fluorescence spectrum(TP-LIF) of NO is obtained by using high power laser as excitation source. A few stronger band can be attributed to A2??X2 ? transition. Some molecule constants about NO which in the ground state are deduced by the spectrum. The nature radiation lifetime of NO which is in the excited state A2? is about 180ns by fitting the curve oflifetime verse pressure.

A 3 x 3 order matrix formalism for describing dispersion system conveniently is achieved by introducing an angular dispersion term based on ABCD matrix formalism. The matrix formalism is used to compute the second and third order time dispersion of the aberration-free stretcher. The same conclusion as the one achieved using the way of routine integral and ray trace is obtained. It is proven that computing the time delay dispersion of any dispersion systems using matrix formalism not only is convenient but also can offer more information about systems. In addition, this way is suitable for any dispersion systems.

A solid-state laser source with flat-top wide beam profile was designed and made. The laser source was mainly made up of an Nd:YAG solid-state laser at 1064 nm and a maximum 267 x collimating telescope. A 2 W laser diode (LD) pumped Nd:YAG laser with flat-concave cavity was adopted as the primary laser source at 1064 nm. Then the output laser (1064 nm) was injected into a collimating telescope. We designed three schemes according to spherical wave theory and chose the best one based on our experiments. We found out the spherical aberration (including axial and off-axial points) must be corrected. At last, an output laser beam with 80 mm diameter, 0.4 mrad divergence angle, > 50 mW output power, and ±10% intensity distribution of cross section, was obtained.

A study on a tunable fiber laser was reported in this paper. Pumping a twenty-meter-long double-clad Yb3+-doped fiber by a high-power multimode LD system, we obtained a tuning range of 42nm in Littrow configuration, with line widths less than 0.08nm. The temporal characteristics of the fiber laser were studied. Some discussions were also presented for the optimization of high-power tunable fiber lasers.

A compact Q-switched diode-pumped double-clad Yb3+-doped fiber laser was described. By using conventional Q-switching technique and exploiting nonlinearity in the core of the gain fiber, the laser operated at a repetition rate of 1.5kHz with an peak power over 13.3kW, pulse width of 5.2ns and pulse energy of 80 µ J. The output wavelength was tunable from 1080nm to 1119nm with a line width less than 0.2nm.

In this paper, Brillouin amplifier is experimental studied. Energy extraction efficiency, energy amplification factor of the seed, and pulse-width compression ratio of the pump to the Stokes output and that of the seed to the Stokes output versus power density of the pump and the energy ratio of the seed to the pump is given.

The output characteristics of linear cavity Yb-doped double-clad fiber laser have been studied theoretically and experimentally. Analytical expressions are evaluated for threshold pump power, output power and slope efficiency of the laser under steady state conditions. The expression of minimum of fiber length for designing a linear cavity Yb-doped double-cladding fiber laser has been given. Then, the Yb-doped double-clad fiber laser has been investigated experimentally. By exploiting various output coupler, output power, threshold pump power and the slop efficiency have been measured. Comparison between the experimental results and theoretical data has been performed. They are in good agreement with each other.

Calculations have been made on the phase dependence of energies of single-cycle pulses with different analytical profiles. For a phase offset of ? between the pulse and carrier, the normalized pulse energy can be expressed as {1 + F cos(2?) —Gsin(2?)} . Analytical expressions of F and G , in term of the ratio of the profile width to cycle period, have been derived for several analytical pulses. With the aid of these expressions the phase dependence of pulse energies have been discussed.

All of the light that reaches a position other than the intended position is referred as stray light. Stray light generated in multi-pass amplifier system forms a lot of ghost image, which not only seriously influence the laser beam quality and propagation properties, but also damage optical components, and is one of major risks that high power laser system operate regularly. Based on the basic principle of geometrical optics, the transmission of beam is analyzed, a ray tracing method of ghost analysis is mentioned, the mathematical and physical model for analysis of stray light and ghost images has been set up, the analysis software has been presented. Taken a simple system as example, these ghost images and the energy density of key components in the system is get correctly. The results are instructive to the actual work of multi-pass amplifier laser design.

When the PDL-2 dye laser was pumped longitudinally by the frequency-doubled DCR-3 YAG:Nd laser, it is found that two coherent radiations are generated by one dye medium ( LDS75 I or LDS750 ). Aside from the expected dye laser output, there appears another coherent radiation generated by a four-wave mixing process. This is caused by the YAG: Nd laser's two longitudinal mode. As far as we know, the four-wave mixing generated in above commercial laser systems hasn't been reported. This discovery is helpful for researches of using above laser systems.

It has been proved that gain volume scaling can be successfully applied to achieve high output power and a compact design. The waveguide material is metallic and diffusion-cooled, thus heat removal is more efficient. It is easy for the annular system consisting of two coaxial tubes to keep in shape and maintain mechanical stability. Annular gain media offer large gain volume with short axial dimensions. The resonator structure, principles of gain volume scaling and characteristics of the output power are presented in this paper. The outer diameter of annular waveguide walls is 20mm; an output power of 75W at wavelength 10.6µm has been obtained from a guide gap of 2.25mm and a gain length of 150mm. The annularly shaped output beam can be used directly for making holes. Moreover, according to its axisymmetrical structure and the law of refraction, by using two small prisms of the exact same material, it is possible to transform the annular beam into a solid beam by careful selection of the incident angle. Further, the diameter of the annular beam varies once the space between two prisms is changed.

In terms of Collins' formuJa, the diffraction integral equations for a piano-concave resonator are presented and transformed to the finite-sum matrix equations. The mode-field distributions and losses of a common piano-concave resonator and that with a Gaussian-reflectivity mirror are calculated. It is shown that the Gaussian-reflectivity piano-concave resonator has good choosing capability for transverse modes, which can be employed in the transverse-flow high-power CO2 laser to improve quality of laser beam.

A general method to analyse an optical resonator is based on the equivalent resonator theory namely the equivalent confocal system theory, but it can not accurately calculate the field distributions ofthe steady-state modes. In this paper, according to the self-reproducing theory and the angular spectra theory for diffraction, the seven-folded stable resonator with circular diaphragms is numerically simulated, and by FFT (Fast Fourier Transform) laser mode-fields in the folded resonator are spatially traced to obtain the stable laser fields. The computed results indicate that the seven-folded resonator with circular diaphragms can easily obtain the fundamental mode, so it can output laser beams of good quality.

The theory of side pumping Nd:YAG solid state laser by high-power array-semiconductor laser cluster are discussed. On the basis ofthat, we design, construct, debugging and survey the performance ofthe laser. The solid state laser device has the following technical specifications: It adopts 3 rank and 3 line, add up to 9 continuous output LD of 20W and 808nm. Nd:YAG laser bar is ?3mm, output wavelength is 1064nm, highest output power is 52.3W, output light mode is continuous multimode, the opto-opto conversion efficiency is 29%.

This paper reports the innovative structure and working properties of a high-power window cooled with solid-liquid phase change. When the power density of output laser beam is 2.5kw/cm2 and the lasting time is 4seconds, the largest thermal deformation of this window is about 0.45um, approximately equal to 1/4 that of normal quartz window, under the same conditions. And the far field divergence angle of the laser beam from the window has been reduced by 1.2 diffraction limits, by contrast to the one from the normal quartz window.

Very high-efficiency, simple, continuous-wave different material-doped Raman fiber lasers are presented. With 1 W Nd:YV04 laser at wavelength 1342 nm pumping, single mode output power above 500 mW (optical-to-optical conversion efficiency of 50%) is simulated operating at l4xx nm. Using high-germanium, high-phosphate and high-borate silicate fiber as the gain medium, and using different geometries, output wavelengths of 1420, 1450, 1480, 1495 nm can be produced respectively, which arejust adapt to pump the C-band and L-band distributed Raman fiber amplifiers.

According to refraction law and total reflection law, the transmission characteristic of laser beam in solid and hollow cone is studied, on this case, the laser fiber refraction coupler which reflect laser with internal cone of hollow cone lens is made, and coupling and transmission of high-repetition-rate spike pulse laser which peak power is MW in fiber are realized, the coupling efficiency get to 80%.

A high power Q-CW array LD pumped Nd: YAG laser was successfully developed by building the model that Q-CW array LD pumped Nd: YAG laser. Using laser rate equation, the geometry formed by the pumping beam meeting laser beam in the resonant cavity was calculated out. In the experiment, two Q-CW array LDs were used. The average output power is 60w and the duty cycle is 20% each. The two Q-CW array LDs were placed along side ofNd: YAG bar at the angle 90°. The pumping beam enters Nd: YAG rod radial so as to fills in the whole medium uniformly, which not only decreases the threshold but increases the slope efficiency. By setting a pair of ? /4 wave plates in cavity steady single mode output can be obtained. Its average output power is 12w, the pulse width is 10-12ns, and the pulse frequency can be variable from 500Hz to 1000Hz.

Steady-state and transient regimes of ultrashort pulse generation are studied for cw solid-state lasers with mode locking by self-focusing. It is shown that the control parameter, which governs the nature of lasing, is the relationship between self-phase-modulation and the saturation intensity of an efficient shutter, induced by the Kerr self-focusing. Numerical modeling based on mapping the parameters of a quasi-soliton ultrashort pulse, considered in the aberration-free approximation, yields results in good agreement with experiments.

In this paper, the theories of CW- laser and pulse laser were analyzed. A novel wide pulse laser is provided. Its pulse width is 1-6ms , the wave length is 1.064 µ m, the energy is 2-6 J. Using high repetition frequency electro-optical Q-switching at a repetition of 1000-5000Hz, it can obtain a series ofshort pulse, whose width is 30-50ns. The pumping of power of the wide pulse laser is decided by IV ? t, where the ? t is the width of electric —pulse. By adjusting ? t, the output power and pulse width can be adjusted . The wide pulse laser can be widely used for machining and therapy.

An all-fiber Yb-doped double-clad fiber laser based on distributed Bragg reflection (DBR) with fiber Bragg gratings (FBGs) is demonstrated. The single transverse-mode wavelength-stable output at 1 .06 µ m is up to 1.18W, with a slope efficiency of 68% and an optical-to-optical conversion efficiency of more than 50%

The phase distribution design process of the pure phase element (PPE) used for quasi-annular beam shaping is introduced in this paper. A new optimization algorithm named Quasi-Gradient Descent (Quasi-GD) algorithm has been developed and used here to meet such design requirement. With a more restrictive sampling mode named precise sampling in the optimization, the simulated result shows that the uniformity of energy distribution on the focal plane is invariant with different sampling intervals and the true beam shaping effect is achieved.

Polarization of CO2 laser light in folded cavity of CO2 laser has been studied in this paper. It is proved that actually laser light in CO2 laser with a folded cavity is polarized perpendicularly to plane which is determined by fold cavity axes, because of difference between reflectivity of mirrors for parallelly polarized laser light and reflectivity of mirrors for perpendicularly polarized laser light in the cavity. It is pointed out that linearly polarized laser beam has to be changed to circularly polarized laser beam to improve cutting quality by the CO2 laser. The heat power given off by reflective mirrors and minimum water flow rate for cooling mirrors have been proposed.

In order to get diffraction-limited beam by Yb:YAG microchip laser, a simple design rule for laser diode (LD) pumped Yb:YAG laser by using M2 factor is presented. The validity of this model is demonstrated by LD pumped CW and QCW Yb:YAG microchip laser experiments. High pump intensity and mode matching between pump and lasing are considered in the end-pumped quasi-three-level microchip laser system. The pumping intensity distributions in laser chip with different pump beam M2 factor and different doped crystal are shown. Experimental setup and results of the established LD end-pumped CW and QCW Yb:YAG microchip lasers are presented. Near diffraction—limited beam is achieved with 40% slop efficiency at 1.049jtm output wavelength. In QCW mode, 16.4µJ pulse energy with TEM00 mode is measured at the repetition rate of 100Hz. The laser pulse relaxation processing and laser pulse width agree with the theoretical results.

In this paper, the pulse Nd:YAG laser pumped with wide-pulse of ms level output Q-modulating serial pulse through high frequency electrooptical Q-modulation. Compared with ordinary pulse laser pumped with pulse of µs level, it can output over ten times higher single high energy. Based on this, the frequency of pulse laser can be doubled more efficiently.

Thermal lens effect is a very important factor in designing stable resonators for high-power solid-state laser pumped by laser diodes. In a symmetric plane-parallel resonator , if the thermal lens of the laser crystal is close to a thin lens, according to the theory of transfer matrix we can get that there is a critical hollow point where the resonator changes from stable region to unstable state, then back to stable region. So we can measure the ultrashort thermal focal length of high-power solid-state laser based on this fact. We used this method to measure the ultrashort thermal focal length of a 100W magnitude Nd:YAG laser. The experimental results have shown this is a simple and effective technique.

The resonance-enhanced multiphoton ionization (REMPI) spectrum of NO has been obtained in the range of 420-480nm with a Nd.YAG pumped optical parametric generator and amplifier. The spectral lines can be attributed to NO X2?(v'' = 0,1) ? A2?(v ' = 0,1) and X2?(v'"= 0) ?* E2?(v ' = 0~4)transitions. In this wavelength range, NO molecules are ionized via the resonant intermediate states A2?+ or E2? and by (2+2) or (3+1) REMPI process. The dependence of ion signals on laser intensity is in good agreement with these results.

A continue-wave (CW) laser-diode (LD) pumped passively Q-switched intracavity frequency-doubling green laser is reported in this paper. We used 3%at. Nd doped YVO4 with size of 3 X 3 X 1mm as gain medium, Cr4+:YAG as a saturable absorber with small-signal transmission T0=94% for passively Q-switch and periodically poled LiNbO3 (PPLN) with the grating period ? =6. 1 µm as a frequency doubler. The laser cavity was consisted of one face of the Nd:YVO4, coated high-reflectance (HR) coating at 1.06 µm and high transmittance (HT) at 0.808 µ m, and a 50mm radius of curvature output mirror with HR coating at 1.06 1 µm and HT coating at 0.53 µm.. A CW 1W LD and a grading-refractive-index lens were used for the end-pumping. The output energy of the green laser is 0.96 µ J with the pulse-width of 19ns. No green-noise problem exists in the green laser, because both the polarizations of fundamental wave and second harmonic wave are the same. Some theoretical results on the passively Q-switching and intracavity frequency-doubling are also reported.

In this paper, Analyzing the stable condition, the mode volume of Gauss beam and thermal characters of the multi-rod series connection Nd : YA G laser with optical transmission matrix, the best way to design multi-rod connection high-power lasers can be given. The experiment results are accordant with the theoretical analysis.

Design of the typical laser diode side-pumped Nd:YAG rod system has been discussed using the conventional ray tracing method in this paper. Firstly introduce two basic matrices, refractional and translational matrix, described the transmission of nonparaxial light ray in the medium without concerning the absorption of light. And then, using those matrices, analyze the distribution of pump light in the crystal respectively under the condition of directly pumped system and indirectly pumped system with a cylindrical quartz rod as focusing lens. From the result of simulation, we compare the advantage and disadvantage of the two pumped method, and mainly consider how to select the diameter of the focus lens and cooling tube, indicate the effect of deionized water and cooling tube have on the pump light distribution in the active material. At last, make some conclusions about the side-pumped Nd:YAG laser system.

Charging technology for solid laser power storage capacity is the key part technology of laser power. Because the capacity voltage always changes in the course of charge, and the equivalent load also changes in a large range, the load characters of charge circuit are strictly required. This paper uses active clamp technique to realize using constant-current to charge storage capacity in the stage of switching tube working at zero voltage, reduce switch loss, get higher charging efficiency.

Based on optical adherence technique, a novel single-to-double clad fiber coupler for high power double clad fiber laser and amplifier is demonstrated. The coupler is made by polishing a single clad fiber at a small bevel angle and adhered to the doped double clad fiber. In this paper, we design and simulate this fiber coupler and fmd the coupling efficiency is sensitive to the fiber's parameter. For given fiber's parameter, the coupling efficiency of 80% can be achieved.

We propose a simple Er-doped fiber laser configuration for achieving stable dual-wavelength oscillation at room temperature, in which a high birefringence fiber Bragg grating was used as the wavelength-selective component. Stable dual-wavelength oscillation at room temperature with a wavelength spacing of 0.23nm and mutually orthogonal polarisation states was achieved by utilising the polarisation hole burning effect. An amplitude variation of less than 0.7dB over 80s period was obtained for both wavelengths.

Both Cr:LiCAF and Cr:LiSAF solid state lasers were developed by Payne et al. As transition-metal vibronic lasers the Cr:LiCAF and Cr:LiSAF exhibit broad emission spectra, long lifetime of the upper laser levels, low nonlinear refractive indices, low thermal lensing, and low excited state absorption that make both of them unique sources for tunable or short pulse lasers. In previous work we had experimentally demonstrated that the Cr:YSO could work as a saturable absorber Q switch for the Cr:LiCAF laser near 780 nm, i.e., the peak of its tuning range. In this work, we theoretically investigate the optical performance of the Cr:YSO Q-switched Cr:LiCAF laser system over its entire tuning range by solving the coupled rate equations. The simulation results indicate that the results obtained numerically are in good agreement with that obtained experimentally. The theoretical simulation also shows that the Cr:YSO may be used as an effective saturable absorber Q switch for the tunable Cr:LiCAF laser over a major portion of its entire tuning range from 725 nm to 840 nm. On the other hand, the Cr:YSO had also been experimentally demonstrated to be an effective saturable absorber Q switch for the tunable Cr:LiSAF laser by Munin et al. The optical performance of the Cr:YSO Q-switched Cr:LiCAF and Cr:LiSAF lasers is numerically studied in this paper.

The absorption cross-section of the Ho:YLF crystal is close to the emission cross-section of the Tm:YAG laser. According to the passive Q-switching theory, a giant laser pulse cannot be generated from the Ho:YLF Q-switched Tm:YAG laser system unless an internal focusing lens is utilized. In a previous work we experimentally demonstrated that passive Q-switching of the 2017-nm, flashlamp pumped Tm,Cr:YAG laser with a Ho:YLF saturable absorber could be obtained with an internal focusing lens. In this paper, we theoretically investigate the optical performance of the Ho:YLF Q-switched Tm:YAG laser system by solving the coupled rate equations. The simulation results indicate that the results obtained numerically are in good agreement with that obtained experimentally. Moreover, we study the passive Q-switching performance of the Ho:YLF Q-switched Tm:YAG laser system as functions of the reflectivity of the output coupler, the initial population of the saturable absorber ground state, the laser pumping rate, and the loss inside the laser resonator. On the other hand, assuming that a polarizer is utilized inside the laser cavity, we explore the passive Q-switching performance of the Ho:YLF Q-switched Tm:YAG laser system when the polarization of the laser light is along different direction between the two saturable absorber principal axes. Effect of the relative position between the saturable absorber and the output coupler is also investigated.

We in this paper report the progress on developing a "laser cooled Cs atomic fountain clock" at NIM. We also present scheme of the "femto-second pulse laser —comb frequencies" which was just started at NIM. As the f-second comb links optical wavelengths to Cs standard frequency and considering that our new Cs fountain clock is desired to achieve an uncertainty in the order of 10-15, these two projects are expected to advance the capability of optical wavelength measurements in this country to a new level in the near future. This work will also lay the technical foundation for developing optical clock as possible candidate for next generation of frequency standard. Key words: wavelength standard, frequency standard, Cesium clock, comb optical frequency.