This PDF file contains the front matter associated with SPIE Proceedings Volume 7844, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Novel design concepts, simulations and experimental results on semiconductor lasers and integrated photonic devices are presented, for both telecom and biomedical applications. It is shown that the Vernier effect can be used to increase the tuning range of a digitally wavelength-switchable semiconductor laser, and to increase the sensitivity of passive and active waveguide sensors. The wavelength switchable laser based on V-coupled cavity has a large tolerance on the accuracy of the setting current. For the middle 50% of the current range corresponding to a wavelength channel, the wavelength varies by only ±0.01nm from the set value for 0.8nm channel spacing and the SMSR is maintained above 38dB. Wavelength switching over 8 consecutive channels is experimentally demonstrated using a single electrode control. The wavelength shift sensitivity of a waveguide sensor based on two cascaded microring resonators with Vernier effect can reach 1300nm/RIU, over an order of magnitude higher than a single ring sensor. A monolithic integrated intracavity biosensor based on V-coupled cavity laser is also proposed and analyzed. By simply detecting the power ratio of two output ports, a refractive index sensitivity in the order of 10^-8 RIU can be achieved thanks to the intracavity sensing mechanism and the Vernier effect.

High brightness InAs/GaAs quantum dot tapered lasers at 1.3μm were first developed with high temperature stability. The devices consisted of a straight index-guided section formed by a ridge waveguide (RW) and a gain-guided tapered section. To enhance the mode filtering, a pair of cavity spoiling grooves had been included. For two different laser lengths L =1.5mm and 3mm with a constant full taper angle φ_TR = 4°, the length of the ridge waveguide section L₂ was varied for 1.5 mm long devices, whose L₂ was 0.5mm and 1 mm, respectively. In case of L=3 mm, the L₂ was fixed at 1mm. For above-mentioned geometries, the light power (P) - current (I) characteristics and the beam quality factor (M²) were presented. The lasers with a smaller L₂ have higher threshold current due to the larger area of the tapered section at fixed total length. The beam quality can be improved with longer L and L₂ at fixed total length L. The M² was lower than the value of 3 measured under different light power, moreover, the M² increased with light power increasing. We also measured temperature dependence of threshold current for two kinds of lasers with L=1.5 and 3 mm. The threshold current was almost constant over a temperature range from 30 to 70°C. It is of important significance for the practical application because that the temperature range overlapped with the operating temperature range. In addition, temperature dependence of the M² for the lasers with L=3 mm was also studied.

A novel beam-shaping method which obtains nearly uniform illumination for a high-power Laser Diode (LD) stack is introduced. Based on the properties of the angular distribution during the Gaussian beams propagate, a flat-topped beam profile can be achieved by the superposition of Multi-tilted Gaussian beams. Due to the theory above, the individual lensing techniques are introduced to shape the beams of the LD stack. Cylindrical lenses are used to control the divergence-angle of the output beams. By adjusting the offset of each cylindrical micro-lens, each output beam on the fast axis gains the different tilted emitting-angle. Meanwhile the beams on the slow axis are also shaped by a large cylindrical lens. Thus the beam-shaping optical system is designed to reconfigure the beams of a high power LD stack to form a Multi-tilted Gaussian beam shape for a 10°×10° field-angle illumination. The simulation results from ASAP software show that uniform illumination can be obtained in the far-field district. With the proper uniformity and high efficiency, the beam-shaping optical system we have proposed for high-power LD stacks can be well suitable for laser illuminator in laser active imaging and detecting system.

We report our experimental results on a two-section DFB laser with a wide tuning range of over 10nm. The device consists of two individually injected gain-coupled DFB sections with a uniform grating pitch. The total device length is only 350um, with 150um for one section and 200um for the other. The threshold current is about 24mA total for the two electrodes. The lasing mode lies on the longer wavelength side of the stop band. In the tuning process, we adjust only one injected current monotonically until the other DFB mode at the shorter wavelength side of the stop band is about to be excited. Then we alter to the other electrode and repeat the process. We found that the shorter wavelength DFB mode can be suppressed efficiently through this method and a mode-hop-free tuning range as large as 11 nm can be obtained. The side mode suppression ratio (SMSR) in optimal conditions is maintained above 45 dB when the wavelength is tuned from 1541nm to 1550nm, while the output power variation is less than 3 dB. To our knowledge, this is the largest tuning range achieved for a two-section DFB laser with a simple uniform grating tuned only by injection current. The device is suitable for applications in DWDM systems as well as laser spectroscopy and lidar sensing.

We present a landslide monitoring approach using a high-resolution distributed fiber stress sensor based on polarizationsensitive optical frequency reflectometry (P-OFDR) technology. The sensing system consists of a polarizationmaintaining (PM) fiber and an OFDR with a high spatial resolution. The PM fiber is used as a distributed sensing element. The OFDR is used to measure the polarization mode coupling loss in PM fiber causing by the external pressure along the PM fiber. With the advantages of frequency domain technique and coherent detection, the sensing system can achieve high spatial resolution, high sensitivity and large dynamic range. By monitoring the mechanical property distribution and variations in the landslide body, the occurrence of the landslides can be predicted accurately. We demonstrate an early landslide warning system based on polarization-sensitive distributed fiber stress sensor, which has a spatial resolution of 5cm, dynamic range of about 70dB and theoretical measuring range of 10km. The warning system is also investigated experimentally in the field trial.

We experimentally and numerically investigated the time delay (TD) signature suppression in a mutually delay-coupled semiconductor lasers (MDC-SL) system. The results show that excellent TD signature suppression can be achieved and all TD signatures are suppressed into background noise level. Meantime, two chaotic sequences are obtained concurrently and the corresponding self-correlation curves exhibit almost perfect δ function profile.

An all-optical power equalization based on nonlinear polarization rotation in a single semiconductor optical amplifier (SOA) is proposed for waveform distortion reduction. Simulations have been done for the degraded data signals to demonstrate the feasibility of the proposed scheme. The primarily simulated results indicated that the switching power is less than 10 mW. The all-optical power equalization mentioned in this paper has promoting potential to improve the signal quality and needs low optical power. Our approach has a simple configuration and allows for photonic integration, which can be constructed by commercially available components.

A novel approach, using a PNA(network analyzer) instead of Spectrum Analyzer in optical heterodyne measurement system, to characterize the frequency response performance of photodetectors is proposed. This scheme synthesize the advantages of both the optical heterodyne technique and accurate calibration technique of PNA. In this paper, two tunable narrow linewidth lasers are used to reduce the errors caused by the variations in the linewidth of the beat signal, and the optical power is accurately monitored and controlled to minimize the noise due to laser output power fluctuates. We analyze the influence of variations linewidth, and associative simulation on this influence is been done. And an error eliminate model is presented to remove the influence of variations linewidth. SOLT calibration technique is used to accurately calibrate the power receiver of PNA. In addition, when configured with an 80 GHz frequency mixer in this measurement system, we can achieve the frequency response measurement of a 80 GHz photodetector since we are using a 40 GHz PNA.

We review our proposed decision-aided (DA) maximum likelihood (ML) phase estimation in coherent optical communication systems with semiconductor laser noises. Our method eliminates the phase unwrapping and argument nonlinear operations. In addition, the proposed adaptive DA receiver has a strong self-adaptation capability to recover the carrier phase effectively without knowledge of the statistics of the phase and additive noises.

Based on the modified coupled-wave theory, the emission characteristics, including threshold gain, photon density distribution in the cavity, and external differential quantum efficiency for second-order DFB lasers are investigated. Numerical simulation results show that for given device structure with wavelength of 1.55 μm, the feedback coupling coefficient and the surface radiation coupling coefficient of the second-order grating have great influence on the emission characteristics of the device. By choosing different duty cycles of the grating, we can change the two coupling coefficients, which affect the emission characteristics. For an overall consideration, an optimal duty cycle of 0.43 is chosen. The optimized results show that the device works without degeneracy modes and spatial burning hole. Besides, the side-mode suppress ratio (SMSR) and external differential quantum efficiency reach as high as 42 dB and 47%, respectively.

The Optically pumped semiconductor disk laser use the InGaAs/GaAs quantum structures as the gain medium, and optically pumped at 808 nm by the Laser Diode. We have got the fundamental output at 1030 nm, and its highest output power is about 60 mW. Then, in straight cavity, we used LBO, KTP, KNbO₃ as second harmonic generation crystal respectively, and obtain the green laser with maximum power of 8 mW. In folding cavity, we employed LBO as second harmonic generation crystal and got the laser at 515 nm with it's maximum power is 11mW. The characteristics of these crystals were discussed. Finally, we simulated the heat distribution of the gain chip by finite-element analysis method, and some measures of improving heat spread and output efficiency of the semiconductor chip.

We demonstrate optical bistability in InP/InAlGaAs multi-quantum well(MQW) semiconductor ring lasers(SRL) which are fabricated by the use of inductively coupled plasma reactive ion etching (ICP-RIE) and can be used in a multi-ring to achieve all-optical storage. Unlike other international reports, the observed optical bistability has unidirectional regime started directly from the threshold, skip the first two regimes and greatly reduce the injection current required in applications. The device described in this article achieves threshold current 56mA which is quite low compared to other reported devices, and some analysis and experiments on the etching depth have been done.

The packaging aspect of the high-speed TO laser module has been investigated in this paper. A conventional TO 56 package is employed for compact and low cost high-speed applications. In the TO header, a special designed RF substrate is developed to minimize the RF reflection and insert loss. The influence of the feedthrough and the TO leads on signal transmission is analyzed using the electromagnetic (EM) method. A testing interface PCB based on the tapered coplanar waveguide (CPW) transmission line is proposed, and simulation results indicate that the coaxial type TO package has an insert loss of 1.5dB at 10GHz. In order to improve the electronic performance of the TO module, the equivalent circuit is built and a bandwidth compensation circuit is introduced, and results show that the 3dB bandwidth of the TO package can extend to 16.3GHz.

A high-speed DFB laser module in butterfly housing has been fabricated in our laboratory, which is operated in direct modulation for Ku-band. The bandwidth of the laser module is measured up to 18 GHz with highly linear characteristics and low relative intensity noise. The input points for 1 dB compression and third order interception of the laser have also been obtained as 23 dBm and 30 dBm respectively, and it can be utilized in analog optical link systems with good performance.

In this paper, a new style state-bistability has been experimentally observed by back and forth sweeping the current of a semiconductor laser nearby its threshold. Moreover, the influence of the injection power on the width of state-bistability loop has been analyzed and discussed in detail.

We experimentally and numerically investigate the chaos synchronization characteristics of mutually coupled system consisted of two semiconductor lasers (SLs) with asymmetrical bias currents. The results show that, for the case of the two SLs with identical free running oscillation frequencies, the mutually coupled system can achieve excellent chaos synchronization under relatively large asymmetrical bias currents. Frequency detuning Δƒ (Δƒ=ƒ₁-ƒ₂, where ƒ₁, ƒ₂ are the free running frequencies of SL1 and SL2, respectively) has obvious influence on the synchronization performance. For the case of the SL1 biased at a relatively much larger current compared with that of SL2, the synchronization performance will be degraded with the increase of the positive frequency detuning (ƒ₁>ƒ₂), while the synchronization performance can be further improved with suitable negative frequency detuning. The simulated results are basically consistent with experimental results.

In this paper, analytical method is employed to analyze the system strain energy and critical diameter of one kind of longitudinally heterostructure nanowire which contains component gradient buffer sections. Based on the critical diameter model of F. Glas in heterostructure nonawires, calculation has been made to research on how does single-layer thickness and total thickness of gradient buffer effect the critical radius of the system. The results illustrate that component gradient buffer layer can effectively reduce the system strain energy, and the thinner the single-layer buffer section thickness , the more obvious the improvement of its critical radius; if the lattice mismatch of the heterostructure nonawires is smaller, the strain energy can be reduced more significantly, also the greater rate of increase of its critical radius. The freedom cut of the nonawires diameter can be realized by controlling the component and thickness of buffer sections. Using Au assistant MOVCD method, we can get high-quality nonawires with component gradient buffer sections, in contrast to the bad quality SEM image of the nonawires without buffer layers, which effectively prove the above conclusions.

Sapphire is an important material for fabricating photonic devices such as light emitting diode (LED). The matter is strongly resistant to wet and dry chemical etching because of its unique physical property. Moreover, there also exist some problems like chipping and edge crack by diamond dicing. Thereby, lots of emerging laser-based techniques have been invented, including various lasers at different wavelength and different technologies, which have gradually become the alternative powerful and efficient methods to dicing this material. Most of investigations on laser dicing sapphire are conducted by UV and ultra-short pulse laser, few by green laser with wavelength of 532nm. So a green laser with wavelength of 532nm and high repetition frequency is employed to dice sapphire substrate. The effects of machining parameters as laser power, repetition frequency, scanning velocity and number of scans on kerf width, kerf depth and aspect ratio are analyzed. Kerf width and depth are measured by optical microscope (OM) and micro-morphology of sapphire is observed by scanning electron microscopy (SEM). Results indicate that narrower kerf, higher aspect ratio and better surface quality can be obtained under the combined processing parameters of medium laser power, lower repetition frequency, medium scanning velocity and multiple scans, which proves green laser to be an effective tool to dice sapphire substrate.

In this paper, the researches and experiments on the feasibility of a common aperture active imaging system using a polarization beam splitter have been presented. The system includes a CCD imaging unit, a semiconductor laser unit, a polarization beam splitter, a linear polarizer, a quarter-wave plate, a telescope objective, a designed laser collimating lens and mechanical assembling structures. According to the analysis with Jones matrix, the system gains remarkably high utilization ratio of luminous energy. Also, the system can reach an illuminating distance of 3km, a laser divergence angle of 0.504° and a degree of uniformity of 83% theoretically. The experiments have been conducted to obtain images of objects at 300m and 3km. From the results, clear illuminated objects can be identified and no impacts of back scattering of atmosphere turbulence have been detected. However, to make this kind of systems more effective, higher demands on the extinction ratio, reflectivity and transmissivity of the polarized components and the uniformity of the illuminating spot should be met.

The Self-Mixing Interference (SMI) effect of a Vertical-Cavity Surface-Emitting Laser (VCSEL) is studied in this paper. The analysis and experiment are presented to verify the dynamics of the VCSEL. The phenomenon is observed and contrasted with traditional interference phenomenon. The output property of VCSEL is modulated by the change of cavity length and feedback intensity. An interferometer using VCSEL self-mixing based on temporal carrier phase shifting technique is studied. Theoretical analysis and simulation calculations are presented and some errors of this method are discussed.

We designed a distributed Bragg reflector mirror with a double-wavelength reflection, which can be used into opticallypumped vertical external cavity surface emitting lasers. This kind of mirror can reflect both the lasing light as a resonance mirror and the pumping light to reflect the pumping light back into absorbing area for increasing the absorption efficiency and improving the thermal characteristics of the laser device. By using GaAs/AlGaAs heterostructure layers and material data, the optical characteristics of the distributed Bragg reflector mirror with a double wavelength reflection at two peaks was calculated. From the calculated results, the two reflection peaks occur at 808nm and 980nm just as the structure design. The reflectivity can be more than 99% for 25-pair DBR. The reflection band width is about 20nm and 25nm for the 808nm and 980nm peaks respectively. This can give a flexibility selection for the double-wavelength distributed Bragg reflector structure design.

In this paper, a simple wavelength-locking scheme for a tunable distributed Bragg reflector laser is presented. A 1*2 wide band fiber coupler as the function of beam splitter forms two optical paths with evenly separated power, one for wavelength monitoring and the other for power reference. For wavelength monitoring, two single mode fiber collimators- one as a transmitter and the other as a receiver-form a collimated light path for laser beam and a highly stable air-paced Etalon inserted between them is used as an optical frequency discriminator to lock the laser wavelengths to several ITU channels maintain 100GHz or 0.8 nm channel spacing in C band. Meanwhile, a photodetector connected with receiving collimator by a FC/PC connector turns the optical signal into electronic signal. For power reference, one of the coupler output pots is directly connected with a similar photodetector. Then wavelength shifting signal proportional to the power differences between two optical paths could be feed backed to the phase region or DBR region for stabilizing the laser output wavelength.

To evaluate the optical influence of illuminant on green color with low chroma (C^*≈1~12) of nephrite from Manasi, three different standard illuminant-daylight D65, incandescent light A and fluorescent light F2 (CWF) were applied during the experiment. Two-way ANOVA was used to analyze the illuminants tested considering the coordinates of lightness L^* and chromaticity a^*, b^*. The results indicate significant differences for L^*, a^* and b^* (p<0.05). Only L^* between D65 and F2 didn't vary significantly (p=0.691) with the multiple comparisons (LSD- test). The green color with higher C^*and L^* were found to be easily influenced by illuminant, and the color-difference was larger and the color appearance varied more obviously while the illuminant as changed. The changes in color parameters and visual effects showed that the D65 light illuminant is more suitable for the evaluation of green nephrite's color grading while light source A can be used during trading.

Cu²⁺, Fe²⁺ and Fe³⁺ of 146 pieces of turquoises from ZhuShan, HuBei province are researched of their contribution to the color of bluish green. Without consideration of its mineral water on the effects of color chroma, the content of these three cations are confirmed by chemical composition analysis, and then their specific contribution to lightness, chroma and hue are quantified within the uniform color space CIE L^*a^*b^*. Consequently, it is considered that Cu²⁺ determines turquoise's vivid blue, and Fe²⁺ makes color changed to green and improves the chroma slightly, as a result it enhances the visual appearance a little too; while Fe³⁺ leads to red and yellow tone and makes chroma descended simultaneously, with its increment, the color appears low saturated brown, and then the color quality reduced.

We have set up a computer automated controlled diode array reliability experiment which can take up 10 to 20 high power cm-bars. Subsequent 25°C and 50°C lifetime tests were completed. According to the method of least squares, the degradation model of cm-bars is obtained. Using the model and weibull++7 software, the extrapolated lifetime of cmbars at 25°C is 7950 hours (2.86×10⁹ shots). We also obtain an acceleration factor 1.88 of resulting in a thermal activation energy of Ea=0.21eV using Arrhenius function. Finally, failure analysis was carried on the gradually degraded devices, the results show that it is the facet degradation which made high power cm-bars degrade during the long time lifetime test.

Large scale optoelectronic monolithic integration for optical fiber communication makes more and more optoelectronic active devices and passive components integrate into a single chip. It is necessary to provide enough wide gain spectrum to satisfy the requirement from each device. In this paper, based the analysis on the gain spectrum of InGaAsP/InP quantum well, the dependence of its gain spectrum bandwidth on the well width and doping concentration was derived. An asymmetric quantum well with the same doping concentration and different well width was design to realize the destination. The simulation results prove that the asymmetric quantum well indeed make the gain spectrum wider. Then the asymmetric quantum wells were grown successfully by low pressure MOCVD at 665°C. The full width at half maximum (FWHM) of 115nm was observed in its amplified spontaneous emission (ASE) spectrum, which was flatter and wider than that of the symmetric quantum wells.

Based on a special sampling technique, we present a special structure for distributed feedback (DFB) lasers. As a conventional equivalent π phase-shift sampling Bragg grating (SBG), this proposed structure also introduces an equivalent π phase-shift into both its ±1^st order channel. Combined with the conventional equivalent π phase-shift, the sampling technique can be used to design and fabricate multiwavelength semiconductor or fiber lasers conveniently.

A distributed feedback (DFB) semiconductor laser with multiple phase shifts based on reconstruction equivalent chirp (REC) technology is numerical studied and fabricated. The simulation results show that the performances of the multiple phase shifts DFB semiconductor laser based on REC technology are nearly the same as the actual multiple phase shifts DFB laser. They have the same P-I curves, the internal power distributions and the output ASE spectra. However, it only changes the sampling structures of the REC based laser with the uniform seeding waveguide grating. So the fabrication of such laser is very easy. In this paper, the fabrication of this structure was realized for the first time to the best of our knowledge. The experimental results show that it has good single longitudinal mode operation even under high injection current with side mode suppression ratio (SMSR) above 55dB even at high injection current.

Hydrogen (H₂) and Argon (Ar) plasma passivation technology was investigated to improve the optical properties of the III-V laser diodes. The main experiment was carried out in the vacuum chamber of the magnetron sputtering system. At first, H₂ and Ar plasma passivation treatment was performed on the GaAs (110) surfaces. The obtained optimum passivation conditions were 65-W radio frequency (RF) of power and 15-min duration, the flow of hydrogen and argon were also 20 sccm.The effect of passivation was characterized by photoluminescence (PL) measurements,the PL intensity of GaAs(110) after passivating was about 10 times of that the unpassivated samples. And then the laser cavity surfaces were treated under the optimum passivation conditions.Consequently,compared with the unpassivated lasers with only AR/HR-coatings, the catastrophic optical damage (COD) threshold value of the passivated lasers by H₂ and Ar plasma treatment was increased by 30 per cent.In the 20 ~ 80°C temperature range, characteristic temperature value of 128K was incresed by 11.3 per cent.The processing is simple and high efficient, can be widely applied to the III-V laser diode devices.

The laser diode(LD) beam propagate through the collimating lens is studied here beyond the paraxial approximation, the ray from the LD entering the lens at coordinates on one face emerges at approximately the same coordinate on the opposite face. The lens delays an incident wavefront by an amount proportional to the thickness of the lens at each point, Further propagation of this field can be adequately represented by the calculation of the Rayleigh-Sommerfeld (RS) diffraction integral, and the stationary-phase method is employed in order to find the asymptotic expansion of the diffraction integral. The propagation optical field after the lens is obtained. The model employed to predict the light intensity at various beam cross sections.

Optical microcavity is a high quality factor micro-cavity with a size of the resonant wavelength. By using of spontaneous emission modulation of organic gain medium, an organic microcavity laser can be achieved. In this paper, a metal Ag-dielectric DBR mirrors mixed organic micro-cavity structure was proposed in this paper. And the influences of center wavelength, growth sequence and the cycle number of DBR, and the thickness of Ag mirror and organic light-emitting layer on performance of Ag-DBR mixed organic micro-cavity were investigated by simulation. And then according to PL characteristics of Alq3:DCM(0.5wt%), an optimal metal Ag-DBR microcavity structure was designed, and based on theoretical calculation results, a corresponding microcavity devices (air/Ag/organic layer/DBR/glass) was fabricated. The experimental and theoretical simulation results are in good agreement. The results show that the calculation method of ours is of great guided significance on the fabrication of metal-DBR organic microcavity lasers.

Based on the beam characteristics of semiconductor lasers, a new parameter for evaluating beam quality of semiconductor lasers is introduced. The shortcomings of M2 factor used in evaluating beam quality of semiconductor lasers are discussed and its limitations are pointed out. Moreover, some important aspects of the beam quality factor are discussed. The main factors to influence collimating the beam of semiconductor lasers are analyzed. Our results give us grounds to make the following conclusions: the new propagation parameter succeeds in its universality and adaptability.

This paper presents a simulation analysis for the threshold characteristics of proton implanted vertical-cavity surfaceemitting lasers(VCSELs) with the aid of optical-electrical-thermal-gain model. The equations for potential, the carrier density, optical transverse mode and thermal field are given. The distributions of injected current, the fundamental transverse mode, carrier and temperature for VCSELs at various aperture radii of 1,2,4 and 6 microns are studied selfconsistently. The threshold injected currents versus the current aperture radii are obtained. The calculated results show that decreasing aperture sizes is an effective method to drop the threshold currents only when the current radii are larger than 2 micron. On the other hand, the threshold currents with the decrease of aperture radii for too small sizes of current aperture. The current aperture radius for low threshold proton implanted VCSEL is found. The threshold currents may drop with improving the confinement of current, while too much small current apertures also damage the threshold. The reason that few VCSEL with smaller aperture radii realize to operate is explained.

A frequency stabilized system of the laser diode is described in this paper. It consists of two parts: the temperature controlling module and the driving current modulating module. The principle and construction of the system are analyzed. Experiments are conducted and data are obtained. It is found that the temperature stability is better than 0.01 K and the stability of the current source is better than 10 uA.

The carriers' distribution of the semiconductor quantum dots are investigated by a rate equation method in this paper. The inhomogeneous broadening of quantum dot's size is considered with a Gaussian distribution. Carrier distribution between different quantum dots size are coupled via the carrier density in the wetting layer, carriers can be captures into the quantum dot energy levels from the wetting layer as well as thermal escaping in reverse, the relaxation effect of the carriers between the different energy level in the same quantum dot is also considered. So a detailed balance between capture and re-emission is established in the different size quantum dot. The carrier dynamics are discussed in the moment paper.

The generation of high-power green laser is important for the numerous applications in industry, medicine, research and even entertainment. In addition, mode-locked lasers operating at ~100 MHz repetition rate, are particularly attractive for nonlinear optics and spectroscopy. Characteristics of high-power, mode-locking green radiation obtained by Nd:YVO₄ at 1064nm in the nonlinear crystals of PPKTP are studied. Two identical highly efficient diode-pumped laser heads placed in a plane-plane resonator are used for the input laser based on theoretically investigation of the thermally stable region of Nd:YVO₄ rod. The PPKTP crystal of Brewster-cut is used in the external cavity configuration, the cavity losses is significantly smaller than for an antireflection(AR) coated crystal cut for normal incident, however, the effective nonlinearity is reduction. Frequency doubling nonlinear mirror(FDNLM) based on intensity dependent reflection in the laser cavity is used for the laser mode-locking. A stable green output power of 510W with pulse repetition rate of 100MHz and net conversion efficiency of η=50% at an input mode-matched power of 2KW are obtained. Meanwhile, thermal effects in the nonlinear crystal severely limit the efficiency of the laser configuration when using high pump power.

Based on the analysis of temperature field generated when semi-insulating GaAs photoconductive switch irradiated by light pulse, the paper focuses on the light damage induced by nanosecond laser pulse with 1.06μm wavelength at high repetition frequencies in switch materials. On the basis of the thermal conduction theory, the transient temperature field in the materials is simulated in a computer by using the finite difference method, the main reasons of damage induced by laser in chip material are analyzed according to simulation results and experimental results of the damage test, and the damage mechanism is discussed.