The output characteristics of an acoustic-optic (AO) Q-switched laser diode (LD) stacks partially end-pumped Nd:YVO4 slab laser was demonstrated. A stable cavity was employed,the curvature radius of input mirror was 500 mm,the transmission of the output mirror was 35%,and the cavity length is 110 mm. The size of the 0.3% Nd:YVO4 slab crystal was 12 mm×10 mm×1 mm,with a-cut and the c-axis along its 12 mm-direction. At pumping power of 104 W and repetition rate of 40 kHz,the average output power of 40 W and single pulse energy of 1 mJ were achieved with an optical-to-optical efficiency of 38.4% and pulse width of 42.2 ns;at repetition rate of 20 kHz,the average output power of 33.3 W and single pulse energy of 1.66 mJ were achieved with the pulse width of 21.1 ns.

By implementing astigmatism compensation of the laser resonator,selecting stable operation conditions as well as optimizing the mode match between light fields and tuning elements,we design and build a stable single-frequency continuous-wave (CW) all-solid-state Ti:sapphire laser with short cavity length. The pump source is a homemade CW single-frequency green laser. Under the pump power of 4 W,the output power of 670 mW at the wavelength of 780 nm is obtained. The intensity fluctuation of the output laser is less than ±0.4% during 1 h,and the beam quality factor M2<1.1. After the laser resonator is locked on a confocal reference cavity with an electronic servo-system,the frequency stabilities are better than ±188 kHz and ±3.28 MHz over 10 s and 15 min respectively in the totally tunable range from 750 nm to 810 nm.

An all solid-state doubling frequency continuous-wave green laser at 542.7 nm is reported. By using a three-mirror folded cavity resonator and pumping the Nd:YVO4 crystal whose doping Nd3+ concentration is 0.2% (atom fraction) with a 20 W output power laser diode (LD),a green laser at 542.7 nm is obtained by reasonably chosing a 10 mm long type II critical phase matching RbTi OPO4 (RTP) crystal to intra-cavity doubling frequency. When the incedent pump power is 19 W,the maximal output power is 2.4 W,the optical-optical conversion efficiency is up to 13%,the power stability in half an hour is better than ±2.8%,and the M2 factor is 1.22.

In laser diode array (LDA) side-pumped module,coupling system with high efficiency and optimized pump distribution is very important. To evaluate different coupling systems,evaluating specifications are put forward. Because different requirements are put on LDA side-pumped modules used in laser oscillator and as amplifiers,different specifications are set up for laser modules and amplifier modules. Calculating results of different pumping intensity distributions of laser modules and amplifier modules show that these specifications can not only show pump depositing efficiency and uniformity of the intensity distribution in the gain modules,but also the matching degree between pump intensity distribution in the laser module and laser oscillating modes.

One part of the saturated absorption spectroscopy on cesium molecules near 780 nm at the absorption band X1Σ+g→B1Πu is obtained. The position of cesium molecular saturated absorption spectroscopy can be determined by 5S1/2(F=2)→5P3/2(F′=2) resonance line of the saturated absorption spectroscopy on 87Rb atom. The five absorption peaks of the saturated absorption spectroscopy are observed. The 780 nm diode laser is stabilized to the “R5” absorption peak. The frequency stability of the laser is better than 1.5 MHz in 800 s. It offers a new method to stabilize the 780 nm diode laser frequency by the saturated absorption peak of cesium molecules. This laser can be used to produce the ultracold ground state cesium molecules,and can be used as the frequency-doubled reference of optical communication range in 1560 nm.

A new high power single emitter laser (F-mount) is reported. This package structure is different from the commercial products structure with C-mount,and it has an advantage of higher thermal conduction. The maximum output optical power of 13.3 W through this package structure is obtained under the testing condition of continuous waves (CW) at 20 ℃ and the laser can still work well. There was no catastrophic mirror-damage (COMD) occurred on it. The maximum output optical power of 30.8 W is obtained under the testing condition of quasi-continuous wave (QCW). Moreover,the following parameters are calculated with coefficient of wavelength-shift versus temperature of 0.278 nm/℃,thermal resistance of 3.18 K/W,the characteristic temperature of 135 K at the threshold current at room temperature,the characteristic temperature of 743 K for the differential efficiency at room temperature. It has lower thermal resistance and better heat sink capability and higher output power than commercial single emitter laser packaged with C-mount structure.

Based on the theory of nonresonant Fresnel phase matching (FPM),tuning characteristics of second-harmonic generation (SHG) wave,the full-width at half-maximum (FWHM) acceptance bandwidth for total internal reflection angle,and the effective nonlinear coefficient of sum-frequency generation in ZnSe and GaP crystals are calculated under different polarization configurations. In theoretical calculation,the parameters,which have been reported to generate the tunable infrared waves by SHG in experiments,are adopted. The optimal quasi-phase-match conditions in ZnSe and GaP are summarized by comparing the simulated results,respectively. The calculated results show a sound theoretical basis for using FPM method to generate tunable mid-infrared wave in isotropic crystals.

Based on the birefringent index dispersion effect,a quartz crystal birefringent filter is constructed with quartz crystal and polarizer for picking up the 590 nm spectral line in an intracavity Raman yellow laser. The operating principle is analyzed by means of Müller matrix and Stokes parameters. The filtering performance is tested by AQ-6315A spectrometer with an intracavity Raman yellow laser as light source. The experimental results show that the 1180 nm spectral line is extracted after filtering,and the purity of 590 nm frequency laser has been ensured. The structure of this birefringent filter is simple and the operation is convenient. At the same time,it does not change the direction of light beam.

A novel global optimization method based on artificial neural network and genetic algorithm is proposed for laser parameters design. An artificial neural network (ANN) is built to simulate the mechanism of the effects of laser parameters on its output power. And then the laser parameters are further optimized with genetic algorithm (GA) with the above obtained network as objective function. As an example,parameters of a typical plano-concave cavity He-Ne laser are globally optimized to testify the feasibility and effectiveness of the method. As concluded from the optimization experiment,the mean square error between the experimental data and simulation data from laser output power network is only 0.0127 mW. The output power of laser with parameters optimized by genetic algorithm is larger than the other laser with the same cavity length,which proves the effectiveness of the method.

In the single-axial rotation inertial navigation system using ring laser gyro (RLG),the errors of the inertial elements can be counteracted automatically because of rotating around the z-direction axis of inertial measurement unit (IMU),so the performance of single-axial rotating inertial navigation system is mostly determined by the estimate precision of z-direction gyro drift. A method to estimate the drift of z-direction gyro based on attitude determination is put forward in this paper,and the theoretical and experimental results are obtained. The experiments show that this method in this paper can estimate the drift of z-direction gyro efficaciously,and the result of navigation is excellent.

We investigate the generation of isolated broadband attosecond pulses for a model of He atom driven by a midinfrared (MIR) laser pulse in combination with a ultraviolet (UV) controlling pulse. By solving the time-dependent Schrdinger equation with split-operator method,the high-order harmonic and attosecond pulse are obtained with MIR and UV pulses,whose wavelengths are 1400 nm and 78 nm respectively. By adjusting the time delay of two lasers,we can enhance the contribution of one electron trajectory and suppress the other electron trajectory. Thus we obtain a shorter isolated attosecond pulse,compared with the pulse produced by the He atom driven by the infrared and ultraviolet fields.

Based on conventional GS algorithm,an accuracy and fast algorithm for phase retrieval is presented. This algorithm,which can be called the accelerated angular spectrum iterative approad,induces a gradient by using the angular transfer functions. The intensity distribution of three planes,e.g. an incident plane and two emergent planes,is employed to retriere the phase distribution of incident optical field. The simulation result shows this algorithm can retrieve the phase distribution of an arbitrary two-dimensional incident optical field in high accuracy. The retrieval accuracy of complicated optical field is greatly enhanced. Robustness and sensibility of this algorithm are evaluated and the algorithm exhibits good convergence.

A system of detecting micro-Doppler effect based on laser coherent radar worked in the 1550 nm wavelength is presented,and experimental research on micro-Doppler effect of detecting the dynamic target is developed. The time domain signal of the returns is decomposed into a set of components that are represented by different wavelet scales. The micro-Doppler features are extracted by sorting the components that are associated with the vibrational/rotational motions of a target and reconstructed by inverse wavelet transform. After the extraction of micro-Doppler features,time-frequency analysis is employed to analyze the oscillation and to estimate the motion parameters. The analysis of experiment results show that micro-Doppler information of the dynamic target can be detected effectively by this system,and tiny vibration can be acquired effectively by analysis of multi-resolution analysis and time-frequency analysis of short-time.

The one-pluse-process plasma electrodes Pockels cell has been established. Five pieces of KDP crystals with 50 mm×50 mm are inserted into the specific areas in the aperture instead of the one-piece crystal with 400 mm×400 mm to investigate the temporal behaviour of the Pockels cell. Owing to the optimum designs,the full aperture high conductive plasma has been created,and the breakdown of the operating gas is stable. The measured switching efficiencies of full aperture are higher than 99.5%. At the neon pressure of 1200 Pa and 2000 Pa,the rise-times of the Pockels cell with full-scale KDP crystal are 78.4 ns and 80.7 ns,respectively.

A streak tube imaging lidar (STIL) system is established to finish a field imaging experiment. With thirty streak images piled up,reconstruction contrast map and range map of a target 702 m away are presented. Relationship between streak images and target detail is marked. The range resolution is better than 0.5 m in the experimental result. Imaging precision affected by streak and divergence of laser beam is discussed.

Accessorial program is actually indispensable to implement the avoidance of ghost image in complex optical systems because common optical CAD software could not accomplish ghost analysis alone. This paper proposes a method that uses programs designed to deal with the output of ZEMAX,so as to export ghost image layout conveniently. The executive results are accurate and the ghost image layouts of complex optical systems are visual and legible. This method could be applied to the high power laser systems design efficiently.

We present a novel spectrum-resolved multifocal multiphoton microscopy (SR-MMM) that is capable of performing fast 2-dimensional (2D) spectral measurements of fluorescent samples with optical sectioning. Fluorescence emission from the excited lines on the sample is spectrally dispersed with a prism,and a CCD array is used to acquire the spectrally resolved image. Spectrally resolved images of 512 pixel×512 pixel can be obtained by acquiring only 128 raw images when a 4×4 excitation foci array is used. Multi-color fluoresent beads,sample slide of a stained lily and pollen particles are used for spectrally resolved imaging experiment. The spectral measurement range is from 450 nm to 700 nm,and the spectral resolution is less than 3 nm.

Optical tweezers,as a powerful tool of manipulation of micro-objects,is commonly used for trapping micro-objects and controlling their movement. Making use of the highly focused heat energy at the laser focus and the transportation ability of the optical tweezers,the process of crystallization,the shape of crystal separating out from solution,and the arrangement mode of the deposition from precipitation reaction can be controlled precisely,which may be used as a means of making micro devices. The laser-induced crystallization method and the laser-assisted precipitation method are used to make micro devices with the copper sulfate and the calcium carbonate as the based materials,respectively. Different factors influencing grow speed of crystals are investigated. The condition of precipitation reaction fitting to the laser-assisted precipitation method is discussed. By comparing,the method of laser-induced crystallization works more efficiently,while the method of laser-assisted precipitation can produce more stable devices. The experimental equipment and the proposed methods not only spread the application domain of optical tweezers but also provide a new way for fabrication of micro devices.

Based on supermodes derived from coupled mode theory,we present the formula to analyze dual core fiber gratings with rectangle-shaped index change,and give its general solution. To the same core with same synchronous uniform grating model,we present a simple express of the solution for each core that can be straightly used in calculation. In this model,the effect of grating is shifting resonant wavelength and adding different additional phases for different wavelengths and it could be used for adjusting the output spectrum of the dual core fiber,and controlling on its additional phase. To the model that gratings are different in index change,we give a numerical simulating result,and discuss its impact on performance.

A multi-longitudinal-mode Bragg reflector (DBR) fiber laser based displacement sensor is reported and implemented. Using cantilever structure,the fiber laser sensor is on the basis of beat frequency demodulation. When the free end of cantilever has a displacement,the longitudinal mode beat (LMB) will change correspondingly. Within the displacement range of -60.17-59.75 mm,the LMB changes from 273.85-272.908 MHz linearly,with a linearity of 0.9993,which agrees with the theoretically analysis. The sensor has a high repeatability and a precision of 3.8×10-3 mm.

A novel optical dense comb filter is proposed,which is composed of many identical linearly chirped fiber Bragg gratings (LCFBG).The spectral characteristics of optical dense comb filter are numerically simulated and analyzed. The results show that the channel spacing of filter is controlled by the length of Fabry-Perot (F-P) cavity which is equal to that of unit grating. By choosing optimal structure parameters of grating,for example,the total chirp,the index modulation depth of unit grating and the concatenated grating number,the reflection spectrum of the filter shows the characteristics of high reflectivity,large bandwidth and multi-channels. For the multi-concatenated gratings,which are easy to be made with a single grating mask,the high reflection of filter can be achieved with a low index modulation depth.

Aiming at the most common and reliable way of packaging-embedded packaging,theoretical and experimental studies on standard packaging design are conducted. Through the analysis of boundary conditions and deformation compatibility conditions of established optical fiber strain transferring analytical model as well as existing main strain transferring characteristic equations,a determined strain transferring characteristic equation is developed,and thus an universal strain transferring relationship is established,which may serve as a basic theoretical model for standard embedded fiber Bragg grating (FBG) packaged structure design. The tested results of packaged models show that strain transferring relationship sestablished according to classic shear lag theory and Ansari′s fiber optical strain transferring analytical model are more reliable for packaged structures containing relative low modulus adhesive materials.

There are wide range of potential applications about long period fiber grating (LPFG),in order to utilize LPFG as sensing element,it is necessary to develop low cost and high precision wavelength demodulation schemes. An high sensitivity technique for LPFG sensor signal demodulation is introduced. A interferometer based on fiber ring mirror and two LPFGs are designed,the wavelength-shift of sensor grating affected by the measured concentration is converted into variation of time-interval between negative-going pulses that is scanning by F-P tunable filter controlled by PZT. The experiment results show that the sensing sensitivity of this system is 0.04 ms·L /g,with the sucrose solution concentration being from 0 to saturated.

Basic principle and merits of fiber Bragg grating (FBG) are introduced. A novelty strain sensor and a temperature sensor with FBG technology are presented. Theoretical and experimental analyses of FBG sensor are implemented. The variations of temperature and strain profiles during curing process are experimentally explored by embedded FBG sensors. However,the thermal drift of FBG strain sensor should be considered during the strain measurement. The experimental results indicate that application of FBG sensor on monitoring the composite in curing process is suitable.

Beams combination is an important way for development of high power solid state lasers,and the phase control electronics contributes greatly to the success of the coherent combining. The method of phase detection for beamlets in a 4 rectangle spot beams array is analyzed,and its mathematical model of coherent combination under phase-locked condition is established. A high-speed wavefront sensor is used to sample the wavefront of one beamlet in laser array,and phase difference between the beamlet and reference beam is detected by the way of heterodyne method from the beat frequency signal,which results from the interference of the reference beam with each beamlet. The phase difference is used to actively control the phase modulator of the beamlet,and then all of the output phases are exactly aligned. Some simulated waveform signals changing versus time are presented during the locking loop is closed,and it is also simulated that the intensity distribution of combined far-field spots changes with phase difference and random aberration among these beamlets,which is compared with that when the locking loop is opened. It is concluded from the simulated results that all output phases of each beamlets can be exactly aligned when the locking loop is closed. The control precision and condition of closing-loop are also analyzed.

A method based on the G-S algorithm is presented,using beam angular spectrum transmit formula to iterate the phase that the compensation for the near-field intensity distribution requires. The iterative algorithm used in the control of beam near-field intensity is presented. Based on this algorithm,an adaptive optics system to achieve control of beam near-field intensity is designed,and numerical simulation and experiments verify the feasibility of this method. The experimental results show that the similarity value ε,which is the distribution of beam near-field amplitude comparing to the ideal distribution of the amplitude,has been improved from 0.718 to 0.966 when the adaptive system working. This indicates that the system is effective in controlling the beam near-field intensity.

Phase-only spatial light modulators are employed to generate controllable wavefront distortion,which is incorporated into a coherent beam combining system to investigate the influence of wavefront distortion in single laser channel on phase control system. Experimental results show that the phase control system is almost not affected in the case of wavefront distortion with small root mean square (RMS) value (i.e.,RMS<π/10). As an increase in the wavefront distortion,the optical phase cannot be totally controlled,residual phase error goes with excursion in the interference patterns exists in the system. When the RMS value of the wavefront distortion is as large as π,the phase control system is in invalidation state and the beamlets cannot be phase locked. Our experimental results present reference for designing and manufacturing high energy laser system based on coherent beam combining.

Based on integral photography and computer graphics,a new method for recording color holograms of virtual 3D objects using single wavelength laser is proposed. Three horizontal parallax only integral photography (IP) images whose colors correspond to tricolor are calculated by simulating integral photography. IP images are illuminated with the coherent beam from the opposite side. Three images of the virtual 3D object are reconstructed and overlapped on a particular image plane by three liner micro-lens arrays. With interfering the reconstructed 3D images and the reference beam after a single exposure,a color hologram is created. Experimental implementation of the new method for a simple case is presented.

NiFeBSi alloy coating and NiFeBSi+mass fractiont 10% nano-SiC composite coating were prepared by laser cladding on the 45# steel,respectively. Microstructural characterization of these coatings were analyzed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM),micro-hardness and tribological properties were measured using Vickers micro-hardness tester and wear testing machine. The results show that the microstructure of the NiFeBSi alloy coating is featured with FeNi3+α-Fe eutectoid structure distributed between the γ(Fe,Ni) dendrites. When mass fraction 10% nano-SiC was added into the NiFeBSi alloy coating,besides FeNi3+α-Fe eutectoid structure,four kinds of carbides are also formed between γ(Fe,Ni) dendrites due to decomposition of SiC particles. The hardness and wear resistance of the NiFeBSi alloy coating are obviously improved due to enhancement of multi-carbide and refinement of FeNi3+α-Fe eutectoid structure.

In present work,the 16 mm thick 11CrNi3MnMoV low alloy high strength steel plates are well joined by dual laser beams welding with hot filler wire,and the strength of joint is higher than parent metal. The microstructure characteristics of primary laser weld,the secondary remelting weld,heat treatment weld,and the effect of microstructure transformation on performances of weld are investigated. The results indicate that,in dual laser beams welding with filler wire,the microstructure of weld is mainly bainite and acicular ferrite,which should be refined by remelting and heat treatment. It’s distinct that the microstructure in reheated zone is similar to that of heat affected zone,and consists of normalized and tempered bainite. Moreover,the acicular ferrite in inner layer weld is much more than that in last layer weld. Meanwhile,a large number of parallel and compact ferrite exist in weld,which improve the tough of weld joint.

The finite element software ABAQUS was used to simulate the processing of constant elastic alloy metal sheet by laser shock waves with semi-die process. The effects of pulse laser energy on metal sheet movement velocity and forming accuracy were investigated. The law of sample velocities in different regions at the same energy was discussed. The results showed that there was no collision between the metal sheet and the concave die when the energy was low. The central node vibrated around the equilibrium position,but the amplitude of vibration decreased gradually and reached zero finally. When the energy was high,the metal sheet collided with the bottom of dies severely,and then the sheet had a reverse movement. The velocity fluctuated slowly for some time and then reached equilibrium state eventually. A good quality waveform sample could be obtained by adjusting pulse laser energies. It was concluded that the software ABAQUS could predict metal sheet velocity in the laser shock forming (LSF) process,and it provides the reference for further study on LSF.

The wide use of galvanized steel in automobile manufacturing brings much challenge to the laser welding process of roof to body-side. The fillet joint is the most effective way to solve the problem of welding pores in the process of laser welding. However,there is little research on this complicated joint process. Focused on this problem,taking metallographic size of welding seams as weld quality criteria,response surface methodology (RSM) is used to study the influence of laser beam on welding seam quality. Key welding process parameters and the optimum welding parameters are concluded.

The related factors to affect WC ceramic-metal composite coatings prepared by laser induction hybrid rapid cladding (LIHRC) are investigated. The results show that,with the preheated temperature of substrate increasing,the efficiency of LIHRC increases. The substrate types also have a significant effect on the efficiency of LIHRC,which is determined by the thermophysical properties (i.e. melting point,resistivity and permeability). With the laser specific energy and the preheated temperature of substrate increasing,the dilution of the composite coating increases,while the dilution decreases with the increase in the powder density per area. Moreover,the efficiency of the composite powder not only depends on the laser processing parameters and the preheated temperature of substrate,but also relates to the weight percent of WC particle and the types of the bonding metal during LIHRC.

In order to study the effect of overlay and laser power density on shockwave in laser shock processing to AZ31B magnesium alloy,the laser induced shockwave was measured by a polyvinylidene fluoride (PVDF) gauge with short rise time and high response frequency and a digital oscillograph. Based on the piezoelectric waves measured in the overlay geometry and direct ablation regime,pressure waves were obtained and compared;the pressure waves acquired in different laser power density conditions were also compared and analyzed. The research results show that the peak pressure of laser shockwave in the overlay geometry is about as eight times as it is in the direct ablation regime,and the duration time of the pulse is extended obviously. Below the dielectric breakdown threshold of the overlay,the peak pressure of laser shockwave is improved with the increase of the laser power density.

0.1-mm-thick PET films and 0.1-mm-thick titanium are joint using laser transmission joining technology. A 3D thermal model based on the finite element theory to simulate the temperature field on laser transmission joining of PET and titanium is established. With the ANSYS parametric design language (APDL) a moving super Gaussian distributed heat source is applied,and the distribution of the temperature field and the time to achieve quasi-steady-state temperature field are gained. Effect of process parameters,including laser power and scanning welding,on the joinging result is investigated,and the calculated joint width is obtained. Experimental data for joint width is collected. Very good agreement is achieved between the calculated values and the measured values. It shows that the model is reliable.

In laser thermal stress cleaving of brittle materials using controlled fracture technique,the applied laser energy absorbed in a local area produces a tensile thermal stress that causes the material to separate along the moving direction of the laser beam. The material separation is similar to a crack extension and the fracture growth is controllable. A three-dimensional finite element thermoelastic calculational model with the heat transfer theory is established to investigate the process when pulsed laser is applied to cut the Al2O3 ceramic plate. The temperature field and thermal stress field at the area irradiated by the laser are simulated. During the laser pulse,the distribution of the tensile stress and compressive stress with depth is obtained. The mechanism of crack propagation is investigated by analyzing the development of the thermal stress field during the process.

Laser-resistance hybrid welding is used to weld LF6 aluminum alloy plates and the process characteristics are analyzed. Thanks to the interaction between laser and resistance heat,the weld depth and cross section area increase evidently. The aluminium alloy joints with full penetration are achieved with low laser power,resulting in the welding efficiency increasing and production cost reducing. The amount of pore in hybrid welding joints decrease compared with that of laser welding. Microstructure observation indicates that the β(Al8Mg5) strengthen phase in weld zone is typical as-cast structure and dispersal distribution,and in heat-affected zone (HAZ) the β strengthen phase clusters grow up together. During tensile test,the hybrid welding joint ruptures at weld zone with ductile shear characteristic. The average tensile strength of hybrid welding joints is 292 MPa,about 83.4% of base metal.

The electronic energy band structure and linear optical coefficient of LiB3O5 (LBO) crystal were calculated with first-principle pseudo-potential plane wave method. The nonlinear optical coefficient of LBO was calculated using coupling perturbation (CP) method. The calculated refractive indices and second-harmonic-generation (SHG) coefficients matched well with experimental results. The electronic density of states on upper part of valence bands and bottom part of conduction bands were calculated. It is found that the 2p orbital of B and O atoms in LBO crystal are hybridized,which is the origin of the nonlinear property.

TaSi2 nanoparticles have been synthesized on highly oriented pyrolytic graphite (HOPG) by ablating high purity TaSi2 target using pulsed laser ablation (PLA) technique. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) are applied to analyze the surface morphology and chemical states of the sample. The SEM results reveal that the average size and surface density of nanoparticles are 10nm and 1×1012cm-2 respectively;The XPS spectra show that the surface chemical elements of the nanoparticles on the HOPG substrate include Ta,Si,C and O. The corresponding investigations confirm the presence of TaSi2 compound. Quantitative analyses indicate the atom ratio of Ta and Si is 1:2.2 utilizing integral peak area sensitivity factor method,which is close to that of stoichiometry TaSi2. The further analysis demonstrates that the formation of TaC is due to the reaction of Ta element and C in the laser ablation process,and the formation of SiC is due to the reaction of Si with C. At the same time,most of the O signals come from the chemical adsorption oxygen on the surface composition of TaSi2 nanoparticles.

Phase change films with SiN/Sb80Bi20/SiN structure are deposited on the K9 glass substrates by direct current magnetron sputtering. Nonlinear optical response of transmittance and reflectance of the films is investigated using a confocal Z-scan technique with a continuous wave He-Ne laser. The results indicate that the transmittance and reflectance at focus both have nonlinear response induced by phase change. The transmittance at focus increases with the increasing of scan power and keeps a saturated value. Formation of phase change micro-area can be achieved at focus of scan laser,and the area will increase with the increasing of scan power. The transmittance of irradiated sample under different powers was studied with in situ repetitive method;and the repetitive power is smaller than the phase change threshold. The results of repetitive Z-scan experiments indicate that the phase change area have a good opto-thermal stability. BiSb films show potential capability for phase change data storage.

The absorption spectroscopy combined with computerized tomography technique is used to reconstruct the two-dimensional (2D) image of gas distribution at uniform temperature and pressure. A new optical scanning system is set up based on four rotation platforms. The 16 cm×16 cm region of interest is scanned within 0.1 s,and 400 projections are calculated according to the laser attenuation caused by gas absorption. With numerical simulation,the assumed model of gas distribution is reconstructed by algebraic reconstruction technique (ART) and least square QR-factorization method. The effect of the concentration boundary constants on reconstruction results is also discussed. The experiments are performed on the reconstruction of 4% NH3 distribution at different heights away from the round flue located in the scanning range,and the images are analyzed further.

提出将激光多普勒测速仪(LDV)应用于车载惯性导航系统提供速度参数。阐述了激光多普勒测量自身速度的基本原理,设计了参考光束型LDV,并运用跟踪滤波、频谱细化及频谱校正技术对多普勒信号进行处理。理论分析与实验表明,参考光束型LDV解决了双光束不能进行离焦测量的难题;跟踪滤波器实时跟踪多普勒信号,去除基底信号和部分噪声,提高了信噪比;频谱细化和频谱校正技术,提高了频谱分辨率,使提取的多普勒频率更接近于真实值,减小了系统的测量误差。LDV可以为车载惯导系统提供有效的速度信息。

At present,the purpose of anti-stealth has been achieved by improving diffuse reflectance signal strength for the most advanced anti-stealth radar,while it is impossible to achieve the fundamental anti-stealth by this method. So,a new radar anti-stealth technology is proposed and by means of straight edge diffraction it can be realized in measuring and tracking stealth flying objects. When scanning the stealth flying object with laser,not only the position and the flying speed of the stealth flying object can be simulated,but also the shape and size can be obtained. Thus,it can be realized in full tracking the stealth flying objects. In addition,the radar of using the principle of straight-edge diffraction has the functions of data encryption.

Scale factor of rate biased laser gyro is precisely measured by calibrating fix-error angle. Common scale factor measurement methods are analyzed according to the characteristics of rate biased laser gyro structure,and it is found that the precision of measuring scale factor is determined by fix-error angle. A method of calibrating fix-error angle is put forward. With this method rate biased laser gyro is installed on position turntable by approximate 45°,the ouput pulses of four different states are measured,then the laser gyro fix-error angle can be calculated,and the formula of measuring scale factor is corrected by the fix-error angle. The experimental result shows that precision of measuring rate biased laser gyro scale factor can be higher than 10-7.

Laser-induced acoustic signal is a new approach for underwater acoustic source,which has much virtue such as high intensity,short pulse and broad frequency. The acoustic signal characteristic of laser-induced breakdown is studied and its corresponding theory model is systemically analyzed. The experimental measure investigation is formed with the high power laser,water tank and high frequency hydrophone. The characteristic of acoustic signal such as intensity,frequency and transmitting is analyzed. Based on the underwater target detection technology,the experiment of underwater target detection is done through laser-induced acoustic signal. The experimental results show that the laser-induced acoustic signal has a salience role during the small target detection. This makes a stride for investigation of laser-acoustic underwater objects detection.

A method based on basic phase measuring deflectometry (PMD) is proposed for testing the aspherical mirror,which uses two reference screens in different distances from the tested mirror. The intensity-modulated patterns are generated on the screens and the images reflected via the tested mirror are recorded by a camera. The original ray of every pixel and its corresponding deflected ray can be constructed using the recorded patterns and phase-shifting technique. Their intersection points and the surface normal are obtained. Then the mirror surface is reconstructed by numerical integration. The procedure for this method is presented,and the computer simulation and experimental results are shown.

To characterize error performance of pulse position modulation (PPM) with optimal demodulation and digital pulse interval modulation(DPIM) whose variable symbol length makes it difficult to analyze performances,an exact symbol error rate (SER) expression is presented as well as its union-bound about PPM based on maximum-likelihood (ML) detection under turbulence channel,and an approximate SER mathematic model of DPIM grounding on transmitted packet is proposed. Appling pairwise error probability (PEP) theory in conjunction with SER,the bit error rate (BER) is also derived. Simulations show that,union-bound analysis of PPM can yield simple analytical upper bounds and approximations to SER,and the performance of PPM influenced more by turbulence is better than DPIM and on-off keying (OOK). DPIM isn′t suitable for simplex communication for its poor BER and SER. The modeling methods and conclusions are applicable to other digital pulse modulations.

Non-coaxial laser confocal microscopy is a novel imaging method of laser confocal microscopy. By observing the sample at an angle to the illumination axis,this method decreases the observation volume of overlap and then improves the axial resolution. Compared with the conventional confocal microscopy,this method has gained wide attention for its advantage that it can improve the resolution,working distance and field of view simultaneously. We summarize the key principle of the non-coaxial laser confocal microscopy,and expand the recent progress and development trend of two typical non-coaxial laser confocal microscopies,confocal theta microscopy and dual-axes confocal microscopy. Finally we briefly introduce our researching plan.