We demonstrate experimentally a fixed two-dimensional (2D) periodic waveguide array by using plane-wave interference in a photorefractive (PR) ferroelectric crystal, and then report on the experimental observation of diffraction management in the 2D "fixed" periodic waveguide arrays.

The existence and stability properties of three-component vector solitons are studied. Linear stability analysis and numerical simulations show that when the power of vortex component is below a threshold, the fundamental component is stable, and the vortex components break up into dipole solitons; the dipole solitons originating from the vector solitons with total zero topological charges are very unique. While if the power of vortex components is higher than that threshold, all soliton components are unstable and break up into independent fundamental solitons. The instability of solitons with total zero topological charges is largely suppressed comparing to that of solitons with total nonzero topological charges.

Using the full Maxwell-Bloch equations which avoid the limitations of slowly-varying-envelope approximation and the rotating--wave approximation as ultrashort pulses are considered, we investigate the coherent control of spectra effects with two color few-cycle laser pulses. We demonstrate that the interference effect of the two laser pulses can substantially modify the behavior of the spectra, higher spectral components can occur even for small area pulses. Moreover, comparing the ω-2ω combination with the ω-3ω scenario, we find due to the deferent superposition of the two kinds of combined laser pulses, the features of these higher spectral components can be much different.

The behavior of population transfer in a double-Λ system driven by linear polarized few-cycle ultrashort laser pulses is investigated numerically. A time-dependent Schrodinger equation without the rotating wave approximation is solved. It is shown that almost complete population transfer can be achieved even when the adiabatic criterion is not fulfilled. Moreover, the robustness of this scheme in terms of the Rabi frequencies and chirp rates of the pulses is explored.

We have observed slow light propagation with a group velocity as slow as 27.52±0.05m/s in a ruby crystal at room temperature. The Gaussian-like pulse signal, which was gained by modulating beam at 514.5nm, was injected into a ruby crystal. The spectral hole effect, attributed to high laser power density, leads to the induced refractive index steep rising. According as this rising, the group velocity of pulse propagation in the ruby becomes very slowly. The experiment result shows that the velocity of pulse propagation depends on the modulation frequency, laser power, the position of crystal and the profile of signal waveform. At the same condition the Gaussian-like pulse obtains much slower velocity than sinusoidal signal.

A frequency-unshifted and backward stimulated scattering can be efficiently generated in one-photon-absorption free but two-photon absorbing materials. Using a number of novel two-photon absorbing dye solutions as the scattering media and nanosecond pulsed laser as the pump beams, a highly directional backward stimulated scattering at the exact pump wavelength can be readily observed once the pump intensity is higher than a certain threshold level. The spectral and spatial structures as well as the temporal behavior and optical phase-conjugation property of this new type of backward stimulated scattering have been experimentally studied. This stimulated scattering phenomenon can be explained by using a model of two-photon-excitation enhanced standing-wave Bragg grating initially formed by the strong forward pump beam and much weaker backward Rayleigh scattering beam; the partial reflection of the pump beam from this grating provides an positive feedback to the initial backward Rayleigh scattering beam without suffering linear attenuation influence. Comparing to other known stimulated (Raman, Brillouin, Rayleigh-wing, and Kerr) scattering effects, the stimulated Rayleigh-Bragg scattering exhibits the advantages of no frequency-shift, low pump threshold, and low spectral linewidth requirement.

For many nonlinear optical process, it is desirable to maximize the product of the intensity and the interaction length. In this paper, very long subwavelength-diameter optical fibers with low optical loss about 0.1 dB cm^-1 were fabricated with a new drawing process by heating the standard single mode fiber with a designed electric strip heater. Pumping the taper fibers with 532 nm mode- locked peco-second laser, we observed exclusive SRS phenomena appeared in these fibers with low pump power and fiber length.

The extinction spectra as well as Hyper-Rayleigh scattering (HRS) signals from three volume silver nanoparticles with aggregate effect have been measured. The morphology of silver aggregates is observed as chain-like aggregate by TEM. Strong enhancements of HRS signals are found when aggregation occurs, and reversed enhancement factor versus particle size is found. The observed size dependence of the second harmonic generation from silver nanoparticle with aggregates effect is explained by assuming surface contribution. Analysis on the extinction spectra and the HRS responses suggests two mechanisms may participate the surface contribution. The first one is arising from the breaking of centrosymmetry at the particles' surface. Another one is the enhanced electromagnetic (EM) field near the particles' surface.

The third-order optical nonlinearity of Fe₂O₃ nanoparticles capped with glutamic acid molecules and bare particles in hydrosol have been investigated by Z-scan technique. The signs and magnitudes of nonlinear refractive coefficients (γ) of these two kinds Fe₂O₃ nanoparticles were obtained. The results suggested that γ was intensively subject to the surface-capping molecules. This phenomenon may be in particular considered with local field enhancement effect related to the refractive index of the media around nanoparticles, and the local field enhancement factor was evaluated by the solution of Laplace's equation.

Although it is expected that, the C=C bond strength will increase after introducing the cyano side-group, thus its photo-stability should be improved. But after careful study, we found that when exposed to light, the introduction of cyano group makes the new molecule alpha'-cyano-4'-nitro-4-N, N-dimethylaminostilbene (CNDS) to isomerize much easier than 4'-N,N-dimethylamino-nitrostilbene DANS. SHG, FTIR, UV-visible absorption and optical pump induced anisotropic absorption measurements were done to support our conclusions. Careful study of the photoinduced optical anisotropy(POA) shows that the isomerization of CNDS is a little smaller than the azo-dye molecule dimethylamino-nitroazobenzene (DMANAB). Explanation was given based on trans-cis quantum yields, de-planar molecular structure which induces small order of orientation and slower thermal relaxation.

The two-photon absorption properties of a new dye have been experimentally studied using the comparable two-photon induced fluorescence method with a pulsed titanium-sapphire laser. This new dye has a two-photon absorption cross-section of 1.7 x 10^-48 cm⁴s/photon at 790nm.

Potential effects were analyzed after incidence of signal wave firstly. Based on the electromagnetic theory and combined with the nonlinear effect of Stimulated Raman Scattering (SRS) of optical fiber, correlative equations were set up for the Raman amplifying Pump wave of optical fiber, Stokes wave and signal wave and the conditional expression which made system gain form positive feedback was given at the same time. It comes to the conclusion that under the condition that system gain positive feedback is satisfied by optical fiber parameters, the input signal wave is amplified when the SRS gain corresponds to unsaturated gain state; the higher is the SRS gain the more is amplification times; the correlation degree is relatively increased when the SRS gain is relatively low in some region.

A composite structure based on linearly chirped fiber Bragg grating which can compensate for dispersion and polarization mode dispersion simultaneously has been proposed and characterized. On one hand, a chirped fiber Bragg grating can be regarded as a filter that is composed of several uniform sub-gratings. Therefore, optical signals with different wavelengths can be reflected at different points of the grating, which will result in different time delays, by which the dispersion compensation can be implemented easily. On the other hand, a chirped fiber Bragg grating has the pressure-induced birefringence effect. In the experiment, a piezoelectric transducer is used to apply the pressure on the linearly chirped fiber Bragg grating. Then the change of reflection spectra can be obtained when the pressure is applied at different points of the grating. From the reflection spectra response, the transverse pressure is found to lead to the split of the spectra of the grating. Through the observation of the group delay characteristics, we find that the differential group delay moves towards a bigger value with the increased voltage, and the maximal range of differential group delay (DGD) is 50 ps. By consequence, first-order polarization mode dispersion (PMD) can be compensated for with linearly chirped fiber Bragg grating. Thus, when the data rate of the fiber communication system is above 10 Gb/s and below 40 Gb/s, the simultaneous compensation of DGD and PMD is necessary and can be achieved by the composite structure.

The quantum transport equation for electrons under intense radiation was solved. The frequency-dependent electrical current driven directly by the radiation field is obtained. The electrical field of the laser radiation is included exactly and the electron-impurity interaction is included up to the second order. Our formalism rests on the solution of density matrix for successive order of photon processes. It is found that as radiation intensity increases, the rate of multiphoton absorption and emission can exceed that of single photon processes. In the strong electron-photon coupling limit, rate of emission is comparable to that of absorption.

We report a theoretical analysis of the generation of broadband and multiple-peak terahertz radiation in aperiodically poled lithium niobate, whose sequence of opposite domains is optimized by simulated annealing (SA) algorithm. The full width at half maximum (FWHM) of the broadband terahertz radiation in our simulation is 0.26 THz. Both of the center wavelength and FWHM can be easily tuned by choosing proper objective functions. Terahertz radiation with wider and flatter FWHM can be achieved by increasing the length of the lithium niobate crystal. The two-peak terahertz generation is also provided as an example of multiple-peak with the central wavelength at 1.68 and 1.80 THz, respectively

The white-light continuum generation (WLCG) has been widely used as a probe beam for the ultrafast time-resolved difference absorbance spectrum or the seeding beam in an optical parametric amplifier (OPA). Therefore reducing the chirp effect in WLCG would be important. We report the study on WLCG in different medium by focusing 800nm laser pulse with a pulse duration of 150fs into 2mm thick CaF₂, 2.4 and 0.5mm sapphire plates, try to find any medium as well as the optical pathlength effect on the chirp of the WLCG. The chirped dispersion of WLCG was determined by optical Kerr effect. The results show that the temporal span of the WLCG is almost independent on the optical pathlength of the medium in the observed spectral region, while it has an obvious dependence on the different media used.

Supercontinuum generation is usually the synergy of some fundamental sophisticated nonlinear processes. Although it is well known that self-phase modulation, stimulated Raman scattering and four-wave mixing etc., are the dominant contributors, the comparative importance of these effects is still blurry to some extent. Based on the extended nonlinear Schrödinger equation describing pulse propagation in the microstructured fiber, we have identified the role of higher-order effects in supercontinuum generation. It is shown that in the initial formation of the supercontinuum self-phase modulation plays a main role while all the higher-order effects play a minor role. After a certain propagation distance the spectral width saturates, suggesting that the supercontinuum in microstructured fiber has a maximum spectral width. During the saturation stage, the higher-order effects exert more important influence on supercontinuum, mainly changing its shape. The third-order dispersion leads to spectral asymmetry, while SRS leads to a red shift of the supercontinuum spectrum. Furthermore, based on our theoretical results, we have discussed the way to controlling supercontinuum generation by using the nonlinear processes of microstructured fiber.

We present a study of the evolutions to spatiotemporal chaos for the extended spatially acousto-optic bistable system in the one- and two-dimensional map lattices. As the system parameters are changed, we obtain the evolutions of the different patterns such as the frozen random state, the pattern selection state, the defect chaotic diffusion state, the defect turbulence state, the pattern competition intermittency state, and the fully developed turbulence state in the one-dimensional extended spatially acousto-optic bistable system. We demonstrate also the evolutions that the homogeneous symmetric states generate symmetry breaking from the four corners and the boundaries and finally lead to spatiotemporal chaos with the increase of the iteration time in the two-dimensional extended spatially acousto-optic bistable system.

Some aspects of the chaotical dynamics of degenerate optical parametric oscillator(DOPO) were analyzed in this paper. The DOPO exhibits not only nonchaotic but also chaotic or even hyperchaotic behavior according to the amplitude of input field and cavity detuning parameters. To indicate chaotic behavior of the system we make use of the spectrum of lyapunov exponents. The topology of the motion is visualized on the appropriate phase portraits. The chaotic and hyperchaotic behavior of the DOPO can be well controlled to enter into periodicity by modulating the input field.

We develop a mathematical model of chirp in a Semiconductor Optical Amplifier (SOA)-based wavelength converters using cross-gain modulation (XGM).Using the model, we study numerically the effects that the chirp of Gaussian pluses and ultra-Gaussian pluses make into the optical signal pluses in Semiconductor Optical Amplifier (SOA), and theoretically analysis the parameters that affect chirp variations.

Signal regeneration is one of the critical functions for the future long-haul transmission distances in all-optical networks. In this paper, the different realization approaches of all optical regenerators are also presented. The theory of FWM is discussed and the application of FWM in Dispersion-Shifted Fiber based optical 2R regenerator is introduced. A realization approach of Optical 3R Regeneration based on Four Wave Mixing will be proposed.

Second harmonic generation (SHG) results from molecules being polarized by an external electric field, often provided by an intense laser beam. The polarizability depends on firstly the intrinsic structural properties of the substance and hence the second order nonlinear susceptibility, and secondly the intensity and polarization direction of the incident light. The polarization characteristics of the beam are therefore of interest. In this paper, we discuss some considerations in SHG microscopy when the incoming beam is circularly polarized, and present some supporting results as well as a question for future work.

Based on the coupled-mode theory, Cherenkov second harmonic generation (CSHG) from a channel waveguide has been analyzed and discussed in detail. The conversion efficiency with only conversion depletion and the conversion efficiency with conversion depletion and propagation loss are obtained respectively, the results show that for the case of low conversion efficiency the conversion depletion can be neglected, but for the case of high conversion efficiency we must take conversion depletion into account, and the propagation loss must be taken into accounted for the both. Furthermore, the nonlinear phase shift (NPS) of the fundamental beam can be maximized by choosing appropriate grating period and appropriate waveguide thickness, which makes the configuration have a promising potential to realize all-optical switches.

6.5 mol.% MgO-doped LiNbO₃ (MgLN) single crystal has been grown by the Czochralski technique. The MgO-doped crystal shows a shift in the absorption edge towards shorter wavelengths and a three orders of magnitude increase in the photorefractive damage resistance compared to the congruent LiNbO₃ crystal (CLN). This material has been periodically poled (PP) at room temperature by applying electric field, and the coercive field is 5 KV/mm, which is about 1/4 of that for congruent LiNbO₃. Periodic poling of 1 mm thick 6.5 mol.% MgO-doped LiNbO₃ substrates has been successfully performed and its operation in a femtosecond second-harmonic generation at room temperature. The performance of quasi-phase-matched second harmonic generation with a 1mm thick PP MgO:LN was compared with that of the second harmonic generation with the PP CLN at room temperature. The PP MgO:LN exhibited better performance.

We review our recent studies into external cavity and intracavity potassium gadolinium tungstate Raman lasers generating output wavelengths in the range 555 nm to 669 nm. We have characterised the performance external cavity Raman lasers pumped by Q-switched 532 nm pump lasers at 5-10 kHz pulse repetition rates generating either single output wavelengths or multiple wavelengths simultaneously. Single output wavelengths are obtained with slope efficiencies up to 68% and maximum output powers ~0.5 W. Simultaneous output at 5 wavelengths (eg., 532 nm, 559 nm, 589 nm, 622 nm and 658 nm) is demonstrated with ~100 mW output power for at least 3 lines. Using the intracavity Raman laser scheme, we demonstrate a 0.3-1.8 W laser that is "user switchable" amongst wavelengths spanning the green to red eg., 532 nm - 555 nm - 579 nm - 606 nm, the wavelengths corresponding to frequency sums and mixing of Stokes and fundamental intra-cavity fields.

Based on near-NCPM (Non Critical Phase Matching) design, type I temperature phase matching of MgO doped LiNbO₃ OPO (Optic Parametric Oscillation) with selected cutting angle at 82 degree. Replacing NCPM with near-NCPM to limit the operation temperature range to a relative low level, a temperature tuned OPO pumped by 532 nm is developed and 800-1700 nm tunable signal lights are achieved. Output pulse energy is higher than 5mJ by a pumping laser of 58 mJ, 532 nm and 6 ns. With frequency doubling of OPO light through a 24.5 degree cut BBO crystal, 2 mJ, 400-800 nm output is obtained by a 19.8-29.2 degree rotating accordingly. The threshold of pump peak intensity for OPO is 57.3 MW/cm². On the position of two times of threshold energy, SRO conversion efficiency is over 11%.

Based on such techniques as clustering, sharing, crowding and elite replacement, a hybrid genetic algorithm (GA) is proposed. This GA can effectively solve the multimodal optimization including the global and local optima in the quasi-phase-matching (QPM) difference frequency generation (DFG). The conversion efficiency and bandwidth, based on QPM-DFG, are optimized by the matrix operator and hybrid GA. Optimized examples for five-, six- and seven-segment QPM gratings are given, respectively. The optimal results show that adding the segment number of QPM can obviously broaden the conversion bandwidth.

Nonlinear optical effects for frequency conversion require a phase-matching condition to efficiently generate a coherent field at the new wavelength. We find that the phase-matching condition can be replaced by a resonance condition when the nonlinear effect takes place in a waveguide directional coupler. We have previously reported this novel resonance phenomenon when the effect of second-harmonic generation occurs in waveguide directional couplers. In this paper, we present our detailed theory. An example of the design of such waveguide directional coupler is presented.

213nm Solid-state laser technology provides an alternative method to replace toxic excimer laser in LASIK system. In this paper, we report a compact fifth harmonic generation system to generate high pulse energy 213nm laser from Q-switched Nd:YAG laser for LASIK application based on three stages harmonic generation procedures. A novel crystal housing was specifically designed to hold the three crystals with each crystal has independent, precise angular adjustment structure and automatic tuning control. The crystal temperature is well maintained at ~130°C to improve harmonic generation stability and crystal operation lifetime. An output pulse energy 35mJ is obtained at 213nm, corresponding to total conversion efficiency ~10% from 1064nm pump laser. In system verification tests, the 213nm output power drops less than 5% after 5 millions pulse shots and no significant damage appears in the crystals.

The refractive index of the periodically poled lithium niobate (PPLN) is about twice as many as the refractive index of the air. When the rotation angle of the periodically poled crystal is bigger, the pump, signal and idler waves can form total internal reflection (TIR) inside the crystal, and the TIR noncollinear quasi-phase-matching (TIR-NQPM) optical parametric oscillator (OPO) can be realized if properly setting the angle of the OPO output coupler synchronously. In this paper, TIR-NQPM OPO based on PPLN pumped with a 1064nm all-solid-state laser is reported for the first time. In our experiment, the angle of rotation for PPLN is 5.57° and 1504~1542 nm of signal wavelength was achieved by tuning the work temperature from 140°C to 250°C. Although adjustment of the cavity is difficult for this method, it broadens the rotation range of angle-tuned QPM OPO. As a result, by one time or more than one time total internal reflections inside the crystal, TIR-NQPM has less limitation of the transverse size of the periodically poled crystal, and the output wavelength range could be increased remarkably.

We studied the interaction between sub-picosecond laser pulse with fused silica. Breakdown threshold, electron collision time and nonlinear propagation dynamics were investigated to study the ionization dynamics and nonlinear propagation process of laser pulse. Electron collision time was measured to be about 1.7fs when the electron density is about 1019cm^-3. Measurements on single shot laser-induced breakdown threshold in bulk fused silica were performed for pulse duration tp ranging from 240fs to 2.5ps when objective with different numerical aperture (NA) were used. It was found that the threshold tendency was depend on effective NA. Numerical simulations based on the nonlinear propagation model revealed that the defocusing effect of the bulk plasma was responsible for the different tendencies. Multi-foci was found at high incident pulse energy and the numerical simulations revealed that it was concomitant with pulse reshaping and refocusing by self-focus.

We report the optical limiting performances of a newly synthesized chromophore, 4 (2'-hydroxy- naphthyl azo ) antipyrine ( H-NAP ) and it's rare earth perchlorate complexes, La ( NAP )₂ ClO₄ and Dy ( NAP)₂ ClO₄, in solution for 20ns pulses of wavelength 532nm. Comparing with the limiting response of C₆0 in toluene (already reported optical limiter), the limiting threshold of H-NAP and it's complexes were found to be much lower. The origin of the optical limiting behavior observed for the samples are under investigation. To elucidate the various phenomena involved, z-scan experiments were performed in all the samples. From the closed aperture data, a negative refractive non-linearity (de-focusing effect) can be inferred in all the three cases. Larger magnitude of n₂ is expected to result in a more effective optical limiting, which implies a lower threshold for limiting and correspondingly lower output above threshold. The second hyperpolarizability of the compounds has a negative sign and is much larger than the reported values for fullerenes. The limiting in H-NAP can be attributed to the large nonlinear absorption of the material and in La (NAP)₂ClO₄ and Dy (NAP)₂ ClO₄, the main mechanism may be de-focusing caused by the nonlinear refractive index. H-NAP and its rare earth perchlorate complexes can hence be considered as very promising materials for optical power limiting.

We have studied theoretically the steady-state nonvolatile two-step, two-color holographic recording performance for both the congruent and the near-stoichiometric LiNbO₃:Fe based on the two-center model (the deep-trap and the shallow-trap centers are Fe²⁺/Fe³⁺ and Nb_Li⁴⁺/Nb_Li⁵⁺, respectively). We compare the amplitudes of the total space-charge fields and the recording sensitivities between the congruent and the near-stoichiometric LiNbO₃:Fe. The results show that the amplitudes of the total space-charge fields in near-stoichiometric LiNbO₃:Fe are larger than that of congruent ones by at least one order of magnitude, while the recording sensitivities of the near-stoichiometric LiNbO₃:Fe are confirmed theoretically to be around two-order in magnitude higher than that of the congruent ones with the same experimental conditions at low intensity region.

We have synthesized two Carbazole-based monolithic monomers, 3-[9-(2-Ethyl-hexyl)-9H-carbazol-3-yl]-2-(4-nitro- phenyl)-acrylonitrile (M1) and (Z)-2-((9-(4-ethylhexyl)-9H-carbazol-6-yl)methylene)-4-oxopentanenitrile (M2), which contain both photoconductive and electro-optic chromophore. The melting point were measured to be 151 oC (M1) and 77 oC(M2) respectively, which are higher than the room temperature. No crystallization of their films is observed at room temperature. One of the monomers M1 exhibits good photorefractive performance. The two-beam coupling gain coefficient of M1 is measured to be 372 cm^-1 at 50 V/um, while the two-beam coupling gain coefficient of M2 is only 17 cm^-1 at 42 V/um. By applying ellipsometric technique, we deduced that the better PR performance of M1 was due that M1 has larger effective electro-optic coefficient. The photorefractive index modulation of M1 was measured to be 6x10^-3 at an electric field of 48.3V/μm. Further investigation on the structure-property relationship has also been demonstrated.

We propose an all-optical demultiplexer with grating array in a photorefractive crystal to achieve high density board-to-board optical interconnects with wavelength division multiplexing (WDM). WDM signal emitted from a board can be branched for each wavelength component and the components are connected to different spatial ports by this demultiplexer mounted on another board. Index gratings, which are induced by illumination of two control beams, are aligned spatially along the signal beam line in a photorefractive crystal. The wavelength component of WDM signal is diffracted by an index grating only when the phase-matching condition is satisfied. This condition is determined by incident angles of control beams and the wavelength of the signal beam. By setting incident angles of control beams appropriately, it can be determined whether a wavelength component of WDM signal is diffracted by the index grating or not. The component can be connected to the desirable output port by arraying the gratings with different grating vector. In our previous study, we have shown that this demultiplexer can branch WDM signal for each wavelength component. In this report, we show that the wavelength selectivity of 0.2nm can be achieved by optimizing the angles of input beams in this demultiplexer. Moreover, we propose a new system in which WDM signal is branched for each wavelength component by angularly multiplexed gratings. By using this multiple grating we can prevent demultiplexer module from growing in size with increasing the multiplicity of signal beam unlike grating array.

We described an electro-optic detection technique-chirped-pulse cross correlation technique for measurement of an electron-beam bunch length. This is a high temporal resolution, single shot technique compared with the other two electro-optic detection techniques: the delay-scan method and the chirped-pulse spectrometer method. In delay-scan method temporal resolution is high, but measurement speed is not ideal. Although in the method of chirped-pulse spectrometer is single-shot with a high measurement speed, the temporal resolution is limited, which has been proved theoretically and experimentally. In chirped-pulse cross correlation technique, resolution and measurement speed are both satisfied. The technique is used to measure electron-beam bunch length in an accelerator.

The soliton transmission system has great potential for providing high speed and long distance communication. However, the polarization-mode dispersion (PMD) of fiber becomes a serious limitation when the bit-rate of systems is over 40 Gbit/s. So it is very urgent to study the influence of PMD on the Soliton communication system. In this paper, we use numerical simulations to calculate the Nonlinear Schrodinger Equations with the PMD effect. In our simulation, we mainly investigate the transmission properties of the Manakov-soliton in optical fibers with PMD at the wavelength of 1550 nm. We discuss the self-trapping effect for a single pulse of Soliton, which can prevent a soliton pulse with PMD from splitting. Then we take the pulse sequences into account, which is more significance in real transmission link, we discuss the timing jitter problem due to the loss of Soliton energy.

Thermally induced rupture of a nonlinear crystal is the primary limiting factor to the attainment of High average power (HAP) in an optical parametric amplifier (OPA). In this paper, HAP scaling behavior in an OPA is addressed in detail by combining thermally induced phase mismatching with thermally induced rupture. Expressions for thermally induced stress are derived and analyzed that can give directions for a HAP-OPA design. When an OPA generates the maximum average output power, the dependence of flaw size on thermo optical material parameters of nonlinear crystals is obtained that is very useful for surface processing, material selecting, properties improving of a nonlinear crystal and new HAP nonlinear crystals developing.

In this paper we firstly study the synchronization of the spatially coupled acousto-optic bistable system using nonlinear feedback technology. Two cases are considered. The first is the same systems with the same parameters. The second is the same systems with the different parameters. The largest conditional Lyapunov exponent spectra are calculated. We give the minimum coupling strength of achieving the synchronization, and the functional relationship between the minimum coupling strength and the system parameters. This method is easy to implement in experiment since adjusting the coupled strength only. It has special importance in practical communication.

Seeker is the key component in the laser guided weapons. Although the seeker has many anti-jamming measures such as the narrowband filter in the front of the seeker and the tracking gate processing circuit in signal processing part, and these anti-jamming measures are always effective for the low power jamming laser. As far as the high power laser which can pass though the filter is concerned, it is easy to make the detector saturate, which will lead the seeker into losing the capturing and tracking capability for the target. In the past ten years, the applied research of organic nonlinear materials which is according to the optical limiting effect has had great development in the laser technology field. And some of these materials have been put into practicability phase. This kind of materials is characterized by its wide absorption spectrum, obvious nonlinear effect and quick response speed, all of which excel the mineral. If this kind of materials can be applied into the laser seeker, it will remedy the laser seeker's defect that its protective capability is weak for the high power jamming laser. The whole applied scheme is present in this paper. And the anti-jamming capability of seeker is analysed constructively before and after the organic matter is applied in the laser seeker. The result indicates that this kind of method is viable in theory.

It is well known that the compressed pulse by the high-order soliton effect in dispersion-shifted fiber (DSF) accompanies by undesired pedestals. In this paper, a novel method by combining a nonlinear Fabry-Perot cavity (NLFPC) and EDFA is proposed for pedestal suppression, which is based on the optical bistability effect of the NLFPC. The numerical simulations demonstrate that obvious pedestal suppression can be realized by selecting reasonably the facet reflectivity of the NLFPC, and the detuning between the central frequency of the input pulse and the resonant frequency of the NLFPC.

BaTiO₃ (BT) nanocrystals doped polycarbonate polymer composite thin films (BT/PC) with different BT concentrations were prepared by spin coating method. Ultra-fine BT (~40-50 nm) nanocrystals with pure perovskite tetragonal phase were synthesized by hydrothermal method. The structure of BT nanocrystals and composite films were studied by means of XRD and TEM. The composite films were poled with a high electric field at a suitable temperature to yield a non-centrosymmetric arrangement and get better electro-optic properties. The Electro-optic (E-O) coefficients of composite films with various BT concentration were also evaluated. The average effective linear E-O coefficient and figure of merit of 20 wt% BT doped composite films were estimated to be 63.1 pm/V and 103.1 pm/V, respectively. The E-O properties of BT/PC composite films were further enhanced by increasing the concentration of the doped BT nanocrystals when the concentration of BT nanocrystals in composite films was low. The orientation degree of BT nanocrystals in PC polymer was detected by measuring the transparency spectra of unpoled and poled composite thin films.

Dielectric barrier discharge (DBD) has numerous industry applications such as ozone generation, pollution control and sterilization of biological samples. The study of process of excitation and ionization is of great use for industry applications. In this paper, the spectrum of DBD in atmosphere is measured by using the special setup with two water electrodes. Nitrogen molecule spectrum (C³Π_u(υ'=0) → B³Π_g(υ"=0~4)) is found at range of 300~800nm. Oxygen molecule spectrum (b¹∑⁺_g → X³∑^-_g) is not found at the range. The excitated energy of nitrogen molecule (C³Π_u(υ'=0)) is bigger than that of oxygen molecule (b¹∑⁺_g). It should be that oxygen molecule spectrum is stronger than nitrogen molecule spectrum. In fact, nitrogen molecule spectrum is very strong, but oxygen molecule spectrum is not found. In order to interpret this contradiction, process of DC discharge in atmosphere has been simulated by the Monte-Carlo computer simulation method. During the period of discharge occurring (the time is very short, about several microseconds), AC DBD can be approximately treated as DC discharge. Elastic collision and inelastic collision considered in air by electron impact, the number of electrons for excitation with E/N is analyzed emphatically. Results show that process of excitated collision of N₂ with electron is far stronger than that of O₂ when E/N varies from 100Td to 1000Td. The probability of the former is about 30 times bigger than that of the latter. So it is explained the above-mentioned phenomenon. The theoretical simulation is in good agreement with the experiment. The results obtained in this work are of great importance to the research of discharges at atmospheric pressure and its applications. The results provide a reference for the controlling of DBD and are of great importance to the industrial applications.

We propose a new all-optical switch by using the nonlinear asymmetric Mach-zehnder waveguide structure which is composed of a narrow nonlinear arm and a wide nonlinear arm. The light-induced index charges in the nonlinear asymmetric Mach-Zehnder waveguide structure break the symmetry of the structure and make the output beam swing in the uniform nonlinear medium. We investigate the characterization by using the beam propagation method. By properly launching the input power, the numerical results show that the proposed nonlinear asymmetric Mach-Zehnder waveguide structure could function as an all-optical switch.

We propose a novel nonlinear all-optical switch by using the phase and power modulation of spatial solitons. The proposed waveguide structure is composed of a straight nonlinear signal waveguide, a nonlinear delay branch, a nonlinear control waveguide, and three nonlinear output guides. By properly launching the control power and varying the length of the delay branch, this nonlinear waveguide structure could really function as an all-optical switch. It could be a potential key component in the application of integrated-optics circuits.

We proposed a new all-optical phase-controlled routing switch contain a two-mode tapered waveguide with the nonlinear cladding. This all-optical device is divided into three sections: the input section, the uniform nonlinear medium section, and the output section. In the input section, the two-mode tapered waveguide is in the center between the linear substrate and the nonlinear cladding. The uniform nonlinear medium section is between the input section and the output section. In this nonlinear medium section, the spatial solitons can be excited. In the output section, three nonlinear guides are used to couple out the spatial soliton excited in the uniform nonlinear medium. The swing effect of the spatial soliton is observed in the uniform nonlinear medium section. By properly controlling the relative phase between the TE0 and TE1 waves, the proposed waveguide device could really function as an all-optical switch.

The swing effect of spatial solitons excited by the butt-coupled linear waveguide is investigated numerically. The proposed waveguide structure is composed of a inclined butt-coupled linear waveguide and a straight nonlinear waveguide. In the input section, the inclined butt-coupled linear waveguide is used to launch the input signal beam. In the straight nonlinear waveguide section, the spatial solitons will be excited and swing in the nonlinear waveguide under the perturbation of the linear-nonlinear interfaces. The swing path of the spatial solitons depends upon the input power level as well as the position and the angle between the linear and nonlinear waveguides. The swing effect of spatial solitons excited by the butt-coupled linear waveguide will be useful for designing all-optical switching devices.

We theoretically investigate the evolvement of dark spatial soliton with cascading quadratic nonlinearity in quasi-phase-matched second harmonic generation. It is shown that the dark solitary wave can propagate stably when background intensity is large enough, in which diffraction of beam can be balanced by the cascading quadratic nonlinearity. We also analyze the influence of phase-mismatch on the stability of dark soliton propagation.

The infrared spectra of congruent LiNbO₃:Fe:M (M= Mg²⁺, Zn²⁺, In³⁺, [Li]/[Nb]=0.946) crystals with 0.03wt% Fe₂O₃ were measured by a FT-IR spectrometer from 3400cm^-1 to 3580cm^-1. The spectra show that OH^- absorption band of double-doped LiNbO₃:Fe:M crystal locates at about 3482 cm^-1 as that of single-doped LiNbO₃:Fe crystals, and it is not shifted to ultraviolet band until the concentrations of M exceeds its concentration threshold. The threshold of damage-resistant ions M is 6mol% Zn²⁺, 4mol% Mg²⁺ and 3mol% In³⁺, respectively. The OH^- absorption band of M-doped (>concentration threshold) LiNbO₃:Fe crystals shifted to 3535, 3525 and 3508 cm^-1, which results from the OH^- stretching vibration in [M_Nb]^a--OH^--[M_Li]^b+ complexes. The influence of valence on the concentrate threshold is also discussed.

An improved two-wavelength prism coupling method is used to measure the third-order nonlinear optical susceptibility χ⁽³⁾ of polymer planar waveguide based on the m-line spectroscopy technique. Due to the optical Kerr effect, the index of the waveguide layer is modulated by the strong pump laser which is incident upon the upper base of the prism perpendicularly to guarantee that it is always coupled into the loading force point with the motorized rotary assembly rotate. Measurement of the third-order nonlinear optical susceptibility χ⁽³⁾ of 1,4-diamino-2,3-diphenoxy-anthraquinone organic dye doped as guests into polymethyl-methacrylate (PMMA) waveguide films is first reported in this paper. A novel method to calculate the third-order nonlinear optical susceptibility χ⁽³⁾ by the tiny change of the probe beam intensity at a certain synchronous angle of the guided mode is demonstrated and gave the value χ⁽³⁾= 3.34x10^-11 esu.

In this experiment, the dynamic two-wave coupling properties of extraordinarily polarized He-Ne 632.8nm laser beam in a Ce:KNSBN crystal were studied with a real-time data-acquisition system. The transmitted pump beam intensity I_p' and the transmitted signal beam intensity I_s' were recorded as a function of time. While the incident beams of two-wave coupling are both with extraordinary polarization, a great fanning will generate and it would affect the two-wave coupling dynamic properties. The dynamic evolution of two-wave coupling had great differences while the total incident beam intensity and the incident beam intensity ratio were different. The coupled-wave equations were modified according to the beam-fanning threshold phenomena and the experimental data. The theoretical calculation results obtained from the modified coupled-wave equations were agree with the experimental data very well.

In this paper, high power and high efficiency operation of an all solid state, quasi-continuous-wave, Ti: sapphire laser is obtained with a laser diode pumped frequency doubled Nd: YAG laser. Discussing the output characters with three kinds of oscillate cavity, we acquire high output power, high light quality Ti: sapphire laser with flat to flat oscillate cavity. The maximum output power is 6.1W at 797nm with pump power of 27W, conversion efficiency is 22.6%, FWHM is 38.4ns and M2 is 3.6. Tuning by birefringent filter, all solid state titanium doped sapphire laser's output wavelength is from 750~950nm and average output power is 4.7W. Pump-tuning method is very important and useful to OPO because it can relieve the OPO of any requirement for crystal translation or temperature variation. In this way, using PPLN crystal with poled period of 20.5mm, 1017~3384nm quasi-continuous-wave output is obtained pumped by Ti: sapphire laser which is tuned from 770 to 820nm. The maximum output power is 1.9W at 1208nm and conversion efficiency is 32%.OPO's average output power is 1.3W in whole output wavelength.

We present a theoretical study of optical bistability and differential amplification, arising as a consequence of the nonlinear Kerr effect in mutually coupled nonlinear microcavity resonators. The dependence of the bistability and differential amplification on various parameters of the coupling range and the resonators is investigated. Multiple closely spaced bistability of the internal intensity in the microresonator is found with appropriate parameters. The results may be useful for a complex logic, memory or switch operation system.

The third-order optical nonlinearities and responses of thin films containing the J-aggregates of a cyanine dye or a squarylium dye were measured using the degenerate four-wave mixing (DFWM) technique under resonant conditions. The sol-gel silica coating films containing the J-aggregates of the cyanine dye, NK-3261, are stable at room temperature and durable against laser beam irradiation. The temporal profiles of the DFWM signal were measured with a time resolution of 0.3 ps, and were found to consist of at least three components, i.e., the coherent instantaneous nonlinear response and the two slow responses with delay time constants of ca. 1.0 ps and ca. 5.6 ps. The contribution of the later was small. The electronic component of the effective third-order optical nonlinear susceptibility of the film had value of as high as ca. 3.0 x 10^-7 esu. We also studied the neat film of a squarylium dye J-aggregates. The temporal profile of the DFWM signal of the neat film of squarylium dye was also found to consist of at least three components, the coherent instantaneous nonlinear response and the delayed response with decay time constants of ca. 0.6 ps and ca. 6.5 ps. The contribution of the slow tail was also very small. The electronic component of effective third-order optical nonlinear susceptibility of the neat film of squarylium dye had value of as high as ca. 3.6 x 10^-8 esu.

In this paper, for the first time we have demonstrated a continuous wave single-pass extracavity frequency doubling by use of MgO doped stoichiometric lithium tantalite (PP-MgO: SLT). The maximum output of the second harmonic green light is 905mW with the pumping power of 7.69W. The second harmonic conversion efficiency is 11.77%. We have theoretically calculated the tolerance of the temperature of SLT SHG which is about 1.5°C. The experimental tolerance of the temperature is consistent with the calculated value.

In this paper the SRS characteristic of a phosphorus-doped fiber made for RFLs is experimentally investigated. At an averaged pump power of 0.5W we observe three spectral lines in the output spectrum, which correspond to the first order Stokes of silica at 1.12μm, the third order Stokes of silica or the first order Stokes of P₂O₅ at 1.24μm, and the fourth order Stokes of silica at 1.31μm, respectively. When the pump power is increased to the maximum value of 2W, there in the spectrum appears a continuum near 1.54μm with a FWHM of more than 50nm. The expected fifth Stokes of silica at 1.39μm and the second Stokes of P₂O₅ at 1.48μm are not observed. We demonstrate that the fiber loss in the region of 1-1.5μm plays an important role in the development of SRS in phosphorus-doped fibers.

A sonoluminescence apparatus based on the original design of T.Gleighton's conical bubble U-tube is built, in which the gas volume in the tube is increased in order to get intense light. Glycol and 1,2-propanediol are used as the liquid media and argon as the gas media. Moreover using photomultiplier and optical spectrometer, the light pulses and the emitted spectra of the conical bubbles have been measured. The results show that the width of the light pulses is of the order of microseconds, which is wider than that of acoustical sonoluminescence's. The spectra for glycol and 1,2-propanediol are similar. Each one is a continuum accompanied three peak bands: one of the peaks is the resonance line of Na, occurs at 590nm;the other two bands lie on two sides of the resonance line. They are at 555nm, blue satellite for sodium, and at 620nm, red satellite. The spectra for glycol using xenon and nitrogen as gas media have also been measured, which are similar to that using argon. When we change the ratio of argon/air in the bubbles in glycol, we find that the light intensity of spectra increase with the increasing of the ratio. So we conclude that the argon could enhance the luminescence of conical bubbles, which is identical to the previous experiments about single-bubble sonoluminescence (SBSL) and mutibubble sonoluminescence (MBSL).

We propose a new method for ultrashort light pulse generation. This method is based on the spatiotemporal instability in dispersive Kerr medium. By formulating a linear instability analysis based on the (3+1)-dimensional nonlinear Schrodinger equation including arbitrary higher-order dispersions, we have disclosed the generic role played by arbitrary higher-order dispersions in spatiotemporal instability. We find that the fourth-order dispersion leads to the appearance of new instability regions which can extend far away from the original instability region. In addition, due to the fourth-order dispersion, temporal instability can develop for any spatial frequencies, and by increasing the spatial frequency, the corresponding temporal instability frequency can be easily increased. Numerical simulations show that the new instability regions can be used to generate a sequence of ultrashort light bullets. The repetition-rate of the generated bullets can be made quite large by increasing the corresponding spatial modulation frequency locating in the new instability region resulted from the fourth-order dispersion.

The Raman effect influence on ultrashort pulse in optical fiber is investigated by using experimental data of delay response function. The frozen of the Raman effect is clarified by using nonlinear Schrodinger equation and finite difference time domain method. In Raman freezing region, a more stable soliton propagation is obtained when the initial power is enhanced.

Changes of LiNbO₃ composition induce refractive index changes. Refractive index changes in LiNbO₃ fabricated by vapor transport equilibration process was investigated using the Z-scan method and Maker’s fringe experiment. In non-critical phase matched second-harmonic generation, the phase matching temperature and the birefringence change for temperature were measured. The phase matching temperature of Li-compensated LiNbO₃ was observed around 230°C and the birefringence change for temperature was smaller than that of congruent LiNbO₃.

We report the results of our investigations on the nonlinear optical absorption and refraction of an organic chromophore, neutral red, both in solution and in solid film forms, using z-scan technique. Z scan experiments were performed with the samples in solution form, in methanol and in solid film form in polyvinyl alcohol (PVA) matrix, using 532nm, 20ns, Nd-YAG laser pulses. The pre-focal peak and post focal valley in the closed aperture z-scan for solution sample are suggestive of a negative optical nonlinearity; where as, the open scan for the same indicates that excited state absorption (ESA) takes over saturable absorption (SA) when the input intensity is increased. For the solid film sample, on the other hand, the closed scan exhibits a sharp pre-focal valley followed by a post focal suppressed peak showing the predominance of two photon absorption (TPA) process. The open scan of the solid film has a dip, which is characteristic of ESA. As both solution and solid samples of this chromophore exhibit nonlinear absorption as well as refraction, neutral red can be a promising material for optical limiting applications.

We present the experimental results on the third-order nonlinearities of several porphyrin and naphthalocyanine derivatives measured by the femtosecond degenerate four-wave mixing (DFWM) technique under resonant conditions. Studies in the solvent effect on the third-order optical nonlinearities indicate that molecular packing in the solutions has significant effects both on the magnitude of the third-order nonlinear optical susceptibility, χ⁽³⁾, and the DFWM response. The electronic component of the molecular hyperpolarizability, γ_e, was evaluated to be in the range of 0.9 x 10^-29 esu to 2.3 x 10^-29 esu for these compounds, where the zinc complex of the porphyrin derivative (ZnTTMAPP) showed the largest γe. These values are two orders of magnitude larger than the reported values measured under non-resonant conditions. The time-resolved results indicate that the relaxation of the excited state population dominates the DFWM response in these macrocycles.

We present the microfabrication of high refractive index-modulated structures written by line scan inside bulk of fused silica with a femtosecond laser at wavelength of 810 nm. The femtosecond laser beam, with duration between 130 fs and 500 fs at a repetition rate of 1 kHz, was focused through a microscope objective with numerical aperture (NA) of 0.10 or 0.25 into the sample. To fabricate high refractive index-modulated structures in fused silica, we investigated the dependence of refractive index change on laser pulse energy, pulse duration, scan speed, and scanning repetitions. The results showed a "triangle region", with pulse duration of 130 fs to 230 fs and pulse energy of 0.35 μJ to 1.5 μJ, for the fabrication of refractive index modulation structures. The refractive index modulation was increased to 3×10^-3 after several scanning passes. Diffractive optical components such as grid, square, circle gratings and Fresnel zone plates have been fabricated by direct writing technique. The structures could be used as diffractive beam splitters, beam shaper and micro-lens.

Darkening and micro-explosions inside ZBaF15 optical glass are investigated by using focused femtosecond laser pulse. With loose focusing, multiple micro-explosions occur in fused silica and ZBaF15 optical glass with single femtosecond pulse. The micro-explosions driven in the center of darkening region are observed in ZBaF15 optical glass. A numerical simulation is given by a model based on the beam propagation in wave-guide channeling induced by the front of excitation pulse. The mechanism of refractive index modification, which induced by femtosecond pulse, is discussed.

Ultrafast lasers have many applications mainly due to its two properties, the ultrashort pulse width and the ultrahigh intensity. Because the former is the main cause of the latter, it is very important to exactly measure the pulse width of the ultrafast laser. Currently, there are several different kinds of experimental methods to measure the ultrashort pulse width. Among those systems for this measurement, the autocorrelator using the second harmonic generation (SHG) is by far the most simple and basic method. This type of autocorrelators usually uses inorganic crystals, such as BBO, as the SHG medium. The thinner medium is necessary for analyzing the shorter laser pulses. However, the polishing process which is necessary for obtaining the optically good surfaces makes it difficult to reduce the thickness of medium as desired. We present an autocorrelator system which overcomes these shortcomings. Our system is based on the SHG using organic polymer. Polymers can be easily prepared in the form of thin film on the strong substrate through the process of spin casting. Thickness less than 1 m can be obtained without difficulties. Furthermore, due to its high nonlinearity, thin film of polymer can produce the bright second harmonic light. Polyurea was used as the second harmonic generation material of the autocorrelator because it has the pretty good transparency. An autocorrelator system based on the 397nm-thick poled polyurea thin film has been developed and used to measure the pulse width of a home-made Ti:sapphire laser oscillator. Then, the system was compared with that based on a 100 μm-thick BBO crystal, which is widely used. The pulse width of laser beam was measured to be 9.8 fs with the former. The value is believed to be more accurate than that of 7.2 fs measured with the latter.

We have demonstrated bandwidth control and reshaping of second harmonic (SH) curve in a periodically poled Ti:LiNbO₃ (Ti:PPLN) waveguide ( period=16.6 um) by using a temperature-gradient-control technique and a local-temperature-control technique. We have achieved more than 13 nm second harmonic phase-matching bandwidth and several useful shapes of SH curve such as almost ideal sinc function, and double peaks in a 74 mm long Ti:PPLN waveguide that has pre-chirped SH curve in room temperature.

We have demonstrated all-optical wavelength-selective single- and dual-channel dropping and wavelength conversion in a periodically poled Ti:LiNbO₃ waveguide which has two second-harmonic phase-matching peaks by cascaded sum and difference frequency generation (cSFG/DFG). Less than -17 dB of channel dropping extinction ratio was observed with coupled pump power of 325 mW and the wavelength conversion efficiency was measured to be -7 dB with coupled pump power of 233 mW.

The main factor of Solitonlike mode creating in the one-dimensional photonic crystals with Kerr nonlinearity was investigated. By matching all boundary conditions we have solved the nonlinear wave equation of MPBGS. The relationship between solitonlike mode and the incident intensity, Kerr coefficient or linear photonic quantum well was calculated. The expression of the localized modes is exactly derived by means of a transfer matrix method, and is solved numerically. Under the linear approximation, the MPBGS sustains localized electromagnetic modes with discrete frequencies. When the nonlinearity is involved, the localized modes develope into solitonlike localized modes that without linear counterpart occur in the gap. They are caused purely by the nonlinear effect. It was found that with the reduction of linear photonic quantum well, rich and varied solitonlike electromagnetic modes appear in the gap. The lower linear photonic quantum well, the less the incident intensity of the first solitonlike mode appear. Although nonlinear is the essential reason caused solitonlike mode, the height of linear photonic quantum well play an important role.

Experimental studies on the mode competition in CW fiber laser pumped Raman fiber lasers with two different F-P cavities are carried out. The first cavity consists of a dichroic mirror and a cleaved fiber end and the second of two dichroic mirrors. Results show that there is drastic competition in the first cavity and much less one in the second because of efficient lasing mode selection of two dichroic mirrors. Reasons for mode competition are analyzed. There are two main kinds of competition in the cavity: one exists between the 440cm^-1 peak and the 490cm^-1 peak in Raman scattering spectrum; and the other is related with long cavity and spatial hole burning. Output characteristic of the laser and probability of different mode wavelengths are also measured.

We present the Nonlinear Optical Loop Mirror (NOLM), the Nonlinear Amplifying Loop Mirror (NALM), a Two - NOLM configuration and a Two - NALM configuration. For all four arrangements the switching equations are derived and computer simulation results are presented. We investigate the switching behavior of two identical NOLM loops and two different NOLM loops in dependence of the length of the nonlinear Kerr fiber, the effective fiber core diameter and the coupling constant α. The same investigations are carried out with two identical NALM loops and two different NALM loops, where additionally the dependence of the gain is considered.

The shapes and durations of generated pulses and the output intensity of ultrashort-pulse (USP) optical parametric generation (OPG) for two cases of λ_p=0.4μm and λ_p=0.8μm are calculated as functions of signal wavelength. The calculation result shows that the conversion efficiency of photon number reduces when the generated pulse frequencies are tuned away from the degenerate point (ν_s=ν_i=ν_p/2), and the signal pulse duration is lengthened when the generated pulse frequencies are tuned far away from the degenerate point. These results can be explained. For this purpose, the intrapulse group-velocity dispersion (IGVD) and group-velocity mismatch (GVM) parameters are calculated as functions of signal wavelength; a new reference of nonlinear interaction length -- pulse-leaving length is introduced to describe the effects of GVM more directly and is calculated as a function of signal wavelength; the phase mismatch for side frequencies of signal, idler and pump pulses,Δk_si,Δk_ps and Δk_pi are calculated as functions of signal wavelength.

Au-SiO₂ nanocomposite thin film is fabricated reproducibly by co-sputtering method with the size of Au nano particles around 2 to 10 nm. TEM images display the irregular shape Au nanoparticles are embedded in SiO₂ thin film with random distribution. A surface plasmon absorption peak of Au nanoparticles is found in absorption spectra. The nonlinear optical properties are measured by confocal Z-scan method with a sub-nanosecond pulse laser (λ=532nm, pulse width 0.71ns, repetition rate 15.79kHz) and high-numerical-aperture objective lens (NA=0.55). Results of the Z-scan show nonlinear optical properties and enhanced transmittance at the focusing position of nanocomposite Au-SiO₂ films. The transmittance can be more than 135% for a 15-nm-thick Au-SiO₂ nanocomposite thin film with an average grain size of around 5 nm.

According to the theoretical analysis and computer simulation, we research the signal linewidth of CsLiB6O10 crystal optical parametric oscillator (CLBO-OPO) caused by the spontaneous parametric emission, the divergence angle of pumping beam, the off-axes pump phase match and the linewidth of pumping beam. The linewidth of signal is very narrow far away from the degeneracy point and the linewidth increased rear the degeneracy point, thus increased rapidly at the degeneracy point is obtained. It is shown that CLBO-OPO has smaller linewidths in type II PM than that of in type I. These results are important for compression the linewidth of OPO signal and useful for construction high power CLBO-OPO laser. We designed a narrow linewidth, wide band tunable optical parametric oscillator in complex resonant cavity and obtained the output linewidth about 0.5nm in the area far away from degeneracy point, and about 6nm in the area rear by degeneracy point in type II PM.

Several near-stoichiometric lithium niobate (LiNbO₃) plates for Periodically poled lithium niobate (PPLN) were prepared by vapor transport equilibrium (VTE) technique. External electric field poling was carried out on these samples. A linear dependence of the switching field on the concentration of anti-site niobium ions was observed. This linear relationship was explained by a two-dimensional model based on the dynamics of domain wall. In this model, the bowing of domain wall and the pinning role of anti-site niobium ions to the movement of domain wall were considered. The pinning-depinning transition of domain wall was attributed to the movement of anti-site niobium ions through the oxygen plane, which is due to the change of domain environment round anti-site niobium ions . A parameter of θ, denoting the ratio between the negative and positive domains round anti-site niobium ions , was introduced. The interaction between anti-site niobium ions and rounding domain environment was analyzed associating with the parameter θ. With the help of the shell-model theory, the force needed for anti-site niobium ions to pass through the oxygen plant was given as 1.696×10^-9 N and the critical θc corresponding to domain reversal was calculated to be about 67° in degree. Using the fitting result of experiment data, the domain wall energy per unit area for LiNbO₃ was also roughly calculated as 0.41 J/m².

In nonlinear optics, single mode laser is a typical example occurring self-organization phenomenon of bistability, oscillation and chaos. Stability analysis and stabilization problem in nonlinear optical systems are problems of great interest. With the development of control theory, impulsive control becomes more and more attractive. Impulsive control can describe some control process which can be used to control the population of a kind of insects by leaving its natural enemies at some proper instant and control the process of reaction by adding chemicals which instantaneously change state variables in a chemical reactor and so on. This paper studies the stabilization problem of single mode laser chaotic system via impulsive control. By using the method of Lyapunov functions, we derive some sufficient conditions for impulsive stabilization. These results are then applied to the single mode laser chaotic system. It is shown that by employing impulsive control method, all the solutions of this kind of chaotic system will converge to an equilibrium point. Finally, some numerical simulation is given to illustrate the efficiency of the obtained results.

We investigate modulation instability (MI) in the distributed fiber amplifier based on a modified Ginzburg-Landau equation. The role of gain dispersion and stimulated Raman scattering (SRS) in MI is identified. It is found that, due to SRS, the MI gain spectrum consists of two parts: the conventional MI gain spectrum and the Raman gain spectrum. Gain dispersion exerts little influence on the conventional MI spectrum, yet it deforms the Raman gain spectrum seriously, mainly by reducing its growth rate. Moreover, as the signal power increases, the bandwidths of the conventional MI and the Raman gain spectrum are simultaneously extended, with the latter spectrum being extended more quickly.

FTIR spectra have been widely used in quantitative analyses of mixed gases. Although Beer's Law regulates the relationships between absorbency and the product of concentration and path length, its deviations have been found rather complicated. Here we present the complexity of quantitative relationships between methane's infrared spectra and concentrations and resolutions. Measurements of the same methane sample's spectra under different resolutions demonstrate that both area absorbency and height absorbency vary with resolutions; spectra at lower resolution have bigger area absorbency for most of the peaks and are more likely to saturate for peaks of strong absorption. Standard methane sample of certain concentration is diluted with super pure nitrogen via mass control flowmeters and continuously passes through a 2-meter gas cell, such that the spectra of methane of different concentrations are collected. The area absorbencies of different peaks are carefully calculated via OMNIC software and results show that peaks with lower absorption are more likely to fit to linearity but more reluctant to changing concentrations. Area absorbencies are integrated through characteristic absorption regions, height absorbencies and area absorbencies are calculated at the two main absorption peaks and measurements show that approximative linearity fits all the areas and the best linearity appears at 1035.6cm^-1.

The internal oscillation of spatial optical solitons in a cubic-quintic nonlinear medium is investigated systemically in their stability parameter region. Both internal oscillations of fundamental soliton and localized optical vortex soliton are determined. Internal modes with and without angular dependence are found. Our results show that internal oscillations exist only when the power of the soliton exceeds a threshold value. We also simulate the dynamics of soliton perturbed by internal modes. Numerical results show that internal oscillations induced by these modes are very robust. Some novel and interesting phenomena are discovered during the propagation process. Evolution of the perturbed state visually appears that the spatial soliton is uniformly (unevenly) breathing or rotating around the propagating axis periodically, the periods approximately equal to that of the internal oscillations.

Identical synchronization and inverse synchronization of chaos are two basic types of synchronization. In this paper, we present a scheme for identical synchronization and another scheme for inversed synchronization in two degenerate optical parametric oscillators (DOPOs) by mutual couple. For realistic values of the systems, we demonstrate two cases of results as follows. (1) Two independent hyperchaotic systems can go into inversed synchronized hyperchaotic oscillations by mutual couple when the coupling coefficient is in the range 0.12< ε<0.50, or 0.07< ε<0.098; (2) If the two DOPOs are mutually coupled and the coupling coefficient is in the range 0.098< ε<0.12 , they will be controlled to enter into periodic states directly and approach periodic synchronization. They will lose synchronization as the coupling coefficient is smaller than 0.07, but controlling hyperchaos can be realized when the coupling coefficient is near 0.01 and 0.053.

In this work, The TiBa glass microspheres doped with Tm₂O₃ for optical resonances of up-conversion emission were designed and preparation. The components of the glass sample are 25TiO₂-27BaCO₃-8Ba(NO₃)₂-6ZnO₂-9CaCO₃- 5H₃BO₃-10SiO₂- 9water glass-1Tm₂O₃ (wt.%). The emission spectra of the TiBa matrix glass and the TiBa glass microspheres under 633nm excitation were measured. The up-conversion emission bands appeared at around 480nm. Many regularly spaced, sharp peaks appeared in the emission spectra of a Tm³⁺-doped glass microsphere . The observed resonances could be assigned by using the well-known Lorenz-Mie Formalism.

We have investigated the dark decay mechanism by measuring dark decay time constants of two-color holograms recorded in undoped and slightly doped near-stoichiometric LiNbO₃ and LiTaO₃ crystals in the temperature range from 50 to 200 °C. All the samples in this work obey an Arrhenius-type dependence of time constant on absolute temperature, and yield nearly same activation energies of 1.08 eV. The results show that proton compensation mechanism dominated the dark decay process. Lifetimes of holograms at room temperature in LiTaO₃ are one order of magnitude longer than that in LiNbO₃ if having the same proton concentration.

We propose a shift multiplexing method for a compact holographic volume storage system by using planar waveguide referencing. In the method, a planar waveguide is used to steer the reference beam and shift multiplexing is implemented by shifting the recording medium. We measure the diffraction efficiencies with respect to the shift distance of the medium for different widths of the waveguide. The selectivity of the storage system can be about 1.0 μm when the width of the waveguide is 0.05 mm. Multiple holograms are stored with a spatial separation of 2.5 μm. By using the planar waveguide, a high storage density can be achieved. As the planar waveguide is already commonly used in integrated optical systems, the whole storage system can become more compact and simpler.

In laser sintering we adopt the method of Nd: YAG frequency doubling to acquire short wave laser in order to obtain fine focus. The paper describes and discusses the method as well as the beam quality of the laser. Based on experiments and theories, we studied frequency doubling in a KTP crystal on Nd:YAG laser by the resonant external ring cavity. The Nd:YAG laser average power is 50w with Q-switch and its frequency is 1005Hz. In the experiment the wavelength of 0.532μm green light output was obtained with 31.4% light conversion efficiency when 1.064μm input average power is 35w. In the green light the proportion of TEM00 model is about 95%. The method is proved to be an effective way to solve the problem of how to get a mini-focus. It is especially useful in the application of laser rapid prototyping. The experimental results for the characteristics of ring cavity frequency doubling were analyzed. The two lasers of 1.064μm and 0.532μm on the beam quality were compared in this paper. The thesis provides the pictures of beam focuses tested with CCD and compares some experimental results with those pictures. A theory of the ring cavity frequency doubling has been put forward in this paper. The sintering effect of the 0.532μm laser was showed in contrast with the 1.064μm laser. The experimental results show that the short wave laser is better for the micro fabrication.

The congruent Nd (Nd: 0. 2 wt %): LiNbO₃ crystals doped with different concentration of MgO (MgO: 1, 3, 5,7mol %) have been grown by Czochralski method in air atmosphere. The crystals were made into samples after polarization, cut and polishing. The infrared absorption spectra of Mg: Nd: LiNbO₃ crystals were measured by using Fourier transform infrared spectrophotometer. The OH- absorption peaks of Mg (1mol %): Nd (0.2wt %): LiNbO₃ crystal and Mg (3mol %): Nd (0.2wt %): LiNbO₃ crystal located at about 3481cm^-1, while that of Mg (5mol %): Nd (0.2wt %): LiNbO₃ crystal and Mg (7mol %): Nd (0.2wt %): LiNbO₃ crystal shifted to 3536cm^-1. The mechanism of OH- absorption peak shifting was studied. The resistance to photodamage of Mg: Nd: LiNbO₃ crystals were measured by light spot distortion method. The results show that the photodamage threshold of Mg (5mol %) :Nd(0.2wt%):LiNbO₃ was the highest(9.0×104W/cm²) among the samples. The mechanism of the photodamage resistance ability of Mg:Nd:LiNbO₃ increasing was investigated. Using a Q adjustable Nd: YAG laser as pumping light, the second harmonic generation (SHG) properties, including the phase matching temperature and SHG conversation efficiency of Mg: Nd: LiNbO₃ were measured by 90 degree angle phase matching technology. The results showed that the SHG conversation efficiency of Mg (5mol %): Nd (0.2wt %): LiNbO₃ was the highest (52%) among the samples at 96°C.

Molecular vibration of several modes in blue-phase polydiacetylene-3- butoxycarbonylmethylurethane (PDA-3BCMU) was real-time observed by 5-fs pump-probe measurement. The contribution of the vibrational wavepackets in the ground state and in the ground state and in the excited state in the signal were separated by multi-channel measurement. The C=C stretching mode in the ground state starts to oscillate π-out-of-phase with the C≡C stretching mode. The structure of PDA-3BCMU in the geometrically relaxed state is not pure butatriene-type but more like acetylene-type. The frequencies of C=C and C≡C stretching modes there were determined by singular value decomposition method to be 1472 ± 6 cm^-1 and 2092 ± 6 cm^-1, respectively. The double and triple bond stretching frequencies in the ground state which are 1463 ± 6 cm^-1 2083 ± 6 cm^-1, respectively.