The experimental study on LD pumped Nd∶YVO_4 laser passively Q-switched by Cr 4+∶YAG was carried out. Especially, the emphasis was on the influence of pump power, initial transmissions of Cr 4+∶YAG and its position in the laser cavity on the pulse width and repetition rate of laser output. The experiment results were analyzed and discussed.

The continuous 2 μm laser with 90 mW is got in a Ti sapphire laser pumped Tm, Ho∶YLF microchip. The pump power threshold and analytical formula are given from rate equation theory. Both the relations of output power with pump power and the conversion efficiency with pump power are obtained. The influence of temperature on laser output power is given.

By the use of a common X-cavity, a self-start KLM Cr4+:YAG laser was obtained while a elaborating designed semiconductor saturate mirror was inserted into the cavity. The shortest pulse width is not longer than 80 fs, the repeat frequency was 120 MHz, and the pulse peak power can exceed 100 W.

In this work, a diode laser end pumped continues-wave polycrystalline 1% Nd∶YAG ceramic laser at 1.06 μm is reported. The lasing threshold was 0.3 W. With an incident pump power of 9 W, an average output power of 2 W was achieved. The optical-to-optical conversion efficiency is 22.2%.

A fiber-coupled diode-end-pumped Nd∶YVO_4 laser with a Nd∶YVO_4 crystal of 0.3 at.-% dopped concentration and 10 mm length was reported in this paper. CW TEM_ 00 mode output of 14.85 W was obtained at a pump power of 27.365 W, resulting in an optical conversion efficiency of 60.49%, and a slope efficiency of 64.5%. The effect of dopped concentration and crystal length on the performance of Nd∶YVO_4 was also analyzed.

High duty-cycle high power 1 cm-bar laser array has been gained. The duty-cycle achieves 20%. The output power is up to 61.8 W at 70 A. The threshold current density J_ th is 220 A/cm 2 and the slope efficiency η_s is 1.1 W/A. The laser wavelength is 808.2 nm.

Two sets of laser system are used, one as a probing beam, the other as an optical pumping beam, to analyze the population distribution of the magnetic sublevel. By scanning the frequency of the optical pumping beam at different frequency, the absorption spectrum is got, from which the population variation of some sublevel can be deduced.

By simulating the Q-switch process of the optical activity crystals in the laser cavity, the experiment setup for studying the electro-optic effect of the optical activity crystals is designed. The phenomenon of interference of the optical activity crystals in the perpendicular polarized light and the parallel polarized light is studied. The optimum configuration for the optical activity crystals to be used as the electro-optic Q-switch in the laser cavity is obtained, and the electro-optic Q-switch is made by using the typically optical activity crystal La2Ga5SiO14 successfully.

A novel broadband acoustooptical (AO) surface acoustic wave interdigital transducer (SAW-IDT) scheme is presented, by using double-tapezia-electrode IDT to compensate high-frequency component of the slanted single-trapezia-electrode IDT. It makes flatter amplitude response and wider bandwidth than those of the single-trapezia-electrode IDT. At the same time, the external compensating network is eliminated. The optimal compensating factor ρ=0.12 and other optimal parameters are found by computer simulation. In the device, Ti-Diffused YX-lithium niobate substrate was applied as optical waveguide, a SiO2/In2O3 film of thickness ~150 nm as ASW waveguide and an acoustical aperture of width 110 μm, in conjunction with N=9 finger pairs. This laboratory prototype shows Bragg acoustooptical bandwidth is 55.3 MHz at 187.7 MHz, its passband slope is 0 and hollow depth is less than 1.0 dB. The RF drive power is measured to be 45 mW at mode-conversion efficiency of 99%. The device is expected to be a integrated optics acoustooptical spectroscopein spectrometer for 1.15~1.65 μm.

Planar optical waveguides were fabricated by Cu +-Na + ion-exchange on soda-lime glass substrate. The effective refractive index was measured by prism-coupling technique at the wavelength of 632.8 nm. Refractive index profile was determined by Inverse-WKB method. Results are compared with mathematical solutions, the best fit to the index experiment data is Gauss function. Therefore, the diffused coefficient of Cu +-Na + ion-exchange at 580℃ is De≈2.223×10 -15 m 2/s.

On the basis of the interference theory, by decomposing the single wave beam, the transmission of polarized light passing through a rotating Taylor analyzer is calculated. By transforming the comparative position of incident light, the normal direction of light transmission plane of the prism, and the normal direction of the glued plane into geometric model, the relationship of incident light and the rotating angle of analyzer is given, according to which it is succeed in explaining the cause of “minute fluctuation” appearing along with the transmission curve of polarizing prism.

The novel manufacturing method for gray-scale masks based on the spatial light modulator has been proposed. In this paper, the basic principle of this method was analyzed, and the corresponding experimental system was fabricated. At the same time, the gray-scale masks of some binary optical elements such as blazed grating, Fresnel lens and Dammann grating have been actually fabricated. This system has intrinsic parallel characteristic owing to its stepper exposure mode, therefore it can improve the manufacturing speed and precision of gray-scale masks with low cost.

The coherent combination of multi-Hermite-Gaussian beams is proposed to describe the flat-topped beams. Based on the Wigner distribution function and intensity moments methods, the analytical equations of beam propagation factor (M 2 factor) and kurtosis parameter (K parameter) of the resulting beam are derived in the general case. It is shown that a flat-topped intensity profile of the resulting beam can be obtained at a certain plane by an appropriate choice of the parameters of Hermite-Gaussian beams. Numerical examples are given to illustrate properties of the resulting beam.

A stochastic resonance (SR) phenomenon was observed by studying the output signal-to-noise (SNR) of the linear model of single-mode laser, which driven by two white noises correlated in the form of a exponential function. Moreover, the influence on SNR by noise (noise intensity, correlated strength and correlation time between noises) and signal (signal frequency and signal strength) was discussed.

Base on the propagation theory of focal shift, the analytical expression of focal shift and relative focal shift were deduced. The effects of flying distance, Rayleigh range and the focal length of focusing lens (or mirror) on focal shift were also discussed.

By using the birefringent crystal YVO_4, a novel scheme of wavelength monitoring in DWDM optical communication systems is presented. The principle of this scheme is analyzed and its feasibility is inspected with experiments. Theoretical analysis and experimental results both show that it can be applied in C-band wavelength monitoring and locking in DWDM systems. As compared with the method of wavelength monitoring by means of the transmission spectrum of a Fabry-Perot etalon, this scheme has advantages such as easy judgment of normal operation wavelengths, high sensitivity of monitoring and easy integration.

In this paper, an algorithm for distributed locating failure in all-optical networks is proposed, whose aim is assure the survivability of optical network. The algorithm avoids the signal transmission between optical nodes, so failure can be located fast. In addition, the algorithm is fit for any scale and any topology.

A novel Interleaver using a modified Michelson interferometer in which its reflecting mirrors are replaced by two Gires-Tournois resonators is presented. On basis of the theory of Michelson interference, a designing principle of the interleaver which has square-like frequency response with zero ripple, wide flat-top, unity contrast, simple structure, and stable performance is given. The device which possesses channel spacing of 50 GHz, ripple less than 0.05 dB, 1 dB bandwidth more than 0.38 nm, and close channel isolation more than 23 dB has been designed.

Delay characteristics of cascaded chirped fiber Bragg gratings (CFBGs) have been theoretically analyzed. Delay ripple increases while the number of cascaded CFBGs increases, and also increases as the wavelength interval between neighbor CFBGs decreases. A way to mitigate the effect, namely using 8-order Gaussian apodization when CFBGs are written is found.

In this paper, a new nonlinear weighted average multidirectional morphological filtering algorithm is proposed to suppress speckle noise. Processing to the images from CO_2 coherent laser radar shows the algorithm can not only preserve the geometrical features of images but also effectively suppress speckle noise in images.

simple and explicit characteristic matrix analysis is used to deal with the holographic mirrors (holographic volume gratings). The continuously varying of the refractive index is considered, and according to the property of holographic material, the small wavenumber approximation is utilized and the periodicity of the grating is used. The calculated precision can be improved by increasing the number of sublayer or developing the terms of power up to higher. The method does not be restricted to region of “near Bragg incidence” and is suitable to solve problems of gratings bounded by two different media. Then the reflectivities, the angular selectivities and the wavelength selectivities of several gratings are computed as numeric simulation

The algorithm of image segmentation is analyzed. The property of low contrast and gray randomly distributed image is considered and the method based on space region variance and gray region variance is proposed for image enhancement and gray segmentation. The experimental results show this method is valid for low contrast image.

A simple all-optical switch based on the photoinduced birefringence is demonstrated in azodye (DR1) doped polymer (PMMA) thin film. The all optical switching effect of the sample is studied at different control beam modulating frequency, different control beam power and different temperature of the sample. In this paper, with the control beam power of milliwatt magnitude, response time in several milliseconds and the depth of modulation above 60% of the all optical switch are obtained.

Wide bandgap semiconductor zinc oxide thin films have been prepared by an electrochemical deposition performed in a chemical cell with three-electrodes, using an aqueous solution of Zn(NO_3)_2 as electrodeposition solution. The obtained ZnO thin films have optical bandgap of 3.35 eV and optical transmittance larger than 80% in the range of 400～2000 nm determined from their optical transmission spectra. XRD pattern indicates hexagonal wurtzite structure without c axis orientation for the ZnO thin films. AFM studies show a dense, irregular polycrystalline film structure with grain size below 250 nm. Stimulated emission occurs at a close ultraviolte wavelength of 403.9 nm under 355 nm optical pumping. When the excitation intensity exceeds a threshold (about 196.8 kW/cm2), very narrow emission peak (FWHM=0.5 nm) emerges and its intensity increases superlinearly with increasing the pump power. The stimulated eimission light is multimode laser relative to incident area and can be observed in all directions, showing a random laser emission due to the formation of a closed-loop path for scattered light in the ZnO thin film.

Depth retrieval method for airborne laser bathymetry is discussed. The corrected method using sea wave and tide and the non-corrected method using KGPS-OTF are introduced. The facts affecting the depth error in airborne laser bathymetry are analyzed. The depth retrieval errors of airborne laser bathymetry using the two methods are evaluated. The accuracy from the corrected method is little higher than that from the non-corrected method, while the non-corrected method is more simple and fast for data processing.

After introducing the temperature real-time measurement system using lasers InGaAs/I and pyroelectric detector LiTaO_3, this paper mainly discusses the effect and control on temperature measurement accuracy by reflection radiation and detector radiation itself. Four measures on improving temperature measurement accuracy are presented: The first is using water-cooled shelter plate and cooling the detector by water. The second is making the detector head the measurement surface as vertically as possible. The third is choosing suitable wavelength bandwidth. The fourth is making electrical compensation. Some necessary calculations and analyses are given Experimental results show that temperature measruement accuracy is suitable for requirement in the range of 400~1200 ℃ after taking these optimal measures.

The commercial picosecond measurement instrument and autocorrelation second harmonic generation (SHG) measurement method have been uniformly calibrated in this paper, which is based on the summary of the present ultrashort laser pulse measurement method. In this experiment, the known delay, which is used as time criteria for calibration of instrument, was generated by the relative optical path difference of Michelson interference light path.

In this paper, the normal Z-scan technique is used to study photorefractive crystal (KNSBN) on theory and experiment. From the result it is found that scattering has an influence on Z-scan. In this paper, the influence has been studied in detail.

A new coaxial feed laser cladding system without carrying gas is researched. Its technical characteristics are as follows: the diameter of focused powder stream about 1.5 mm, focusing length from 15 to 35 mm adjustable,omnidirection, open space and covenience for operating, uniform distribution of microstructure, chemical contents and microhardness, as well as high powder efficiency about 60%～80%.

Strengthening the important aerial aluminum alloy material, 7050T7451, 7050T7452 by laser shock processing (LSP) technique with the home made device. Testing the fatigue life. σ_m-N curves which show the relation of fatigue stress level and fatigue life of material were given, the result showing, after LSP, fatigue life of 7050T7451 increases to 435% of non LSP sample under 67.3 MPa stress level, fatigue life of 7050T7452 increases to 518% of non LSP sample under 81.4 stress level. Also researching the mechanism of LSP on 7050 aerial A-alloy, the result shows the surface of the test piece has biggiesh residual compressive stress, and biggish internal dislocation density.