This article has reported the detailed analysis about the error in the experimental measurement of laser equation of state. A kind of matrix method to calculate the uncertainty of state parameter was put forward and applied to the error estimation in the experiment with Al-Cu impedance-match target. The shock adiabatic data of Cu with the pressure up to ~2.24 TPa and the relative uncertainty of shock velocity of ~2% have been also presented.

The experiment of laser-driven Rayleigh-Taylor (RT) instability on Shenguang II (SG-II) facility has been presented. A Ni-like silver soft x-ray laser at 13.9nm has been used as a probe to take radiography of the modulation target RT instability first time. The modulation target is irradiated by a laser beam at 527nm of wavelength, 1500J of energy and 2.4ns of pulse width (FWHM), which is focused to intensity of 4×1014Wcm-2 on the target by a lens array. The evolvement of RT instability has been observed clearly. The results obtained by numerical simulation agree with that given by experiments.

In order to realize less than 30μm the pointing error of the main laser and the large focal spot irradiation uniform on target surface better than 10% of the additional beam in ＂Shenguang- Ⅱ ＂ laser facility, a physical design of final optics assembly（FOA） has been proposed. Using finite element method, the static and dynamic states about the main machine components of FOA and the integral ICF target chamber are analyzed and the design of FOA is optimized. And using mathematics simulation, lens array has been analyzed and designed based on the focus lens about unit number, radius, thickness, long axis and short axis. Experimental results show that the pointing error of main laser on the target is 28.9μm , the large focal spot is 1000μm× 500 μm and the large focal spot irradiation uniform is 12.0%.

To obtain a large-aperture high damage threshold grating compressor for a perawatt laser system, the multi-piece dielectric membrane tiled grating is an effective method. In order to avoid the influence of tiling error on the temporal and spatial characteristics of grating, the rotation error needs to be controlled in 1 μrad. Therefore, the zero-order and first-order diffracting light is used to monitor the rotation error independently. 0.1 pixel accuracy can be achieved by location of the center of fringe with quadratic curve-fitting, which can detect rotation error about 0.5 μrad. For the requirement of high precision is confined by the controlling device and environment, real-time monitoring and adjusting are necessary to maintain the grating posture, and feedback the deflection to the installations to maintain the sub-grating position. The deviation can be maintained within 0.5 μrad for a long time. Experiments show the rotation error real-time monitoring and adjusting about tiled gratings can meet precision and stability requirements.

In order to take full advantage of amplifier gain-bandwidth, and obtain a shorter pulse with higher power in the terminal, it is necessary to conduct a spectrum shaping before the seed pulse being injected into the main amplifier chain to compensate the effect of gain narrowing. A new method, based on the spatial grating with variable line-space for spectrum shaping of chirped laser pulse with the central wavelength at 1053 nm and line width 6 nm, is presented. The rigorous coupled-wave theory is used to analyze the characteristics of grating diffraction, and the results indicate that this method produces no phase distortion. The diffraction efficiency, as a function of the depth and period of groove, incidenct angle, and incident wavelength, is calculated and analyzed, respectively. With proper grating parameters, the spectrum modulation depth from 0.5% to 84% can be achieved.

Alignment errors of sub-aperture gratings in the optical design of tiled gratings and tiled grating compressors are almost unavoidable. It is important to study the relation between alignment errors and temporal properties of the tiled graing. Analyzed by pulse compression theory, the relation between these alignment errors and focused pulse width broadening is obtained. And the numerical calculation results show that planar alignment errors have much more important influences on the pulse duration, which must be controlled within 21.08 μrad, and the groove-width difference also affects the pulse duration severely, so the ratio between the groove-width difference and groove-width must be controlled within 10-5. From the point of view of eliminating angular dispersion, the planar tilt errors and groove parallelism can ompensate each other, and the groove-width difference and planar errors of tip can also compensate each other.

Introducing the tip-tilt and piston error as the parameter and defining the aperture function of the tiled-grating, far-field property was analyzed with Gaussian beam incidence using the theory of Fourier angular spectrum. The results showed that the output beam was Gaussian while the center of the envelope shifted, the shift magnitude was determined by angle errors and beam size. The phase difference caused by piston error translated with the tiled-grating compressor, the focal spot was affected by both non-integral number of grating space and out-of-plane piston error. Numerical simulation showed the effect on the spatial characteristic of the tiled-grating compressor due to alignment errors.

Spectral clipping effect in a chirped pulse amplification laser system is developed in this paper. A grating-size-limited stretcher/compressor as well as an amplifier can alter the spectrum profile of an ultrashort pulse, so the temporal profile will be influenced. We present a model of spectral clipping effect and calculate the wavelength-dependent spectral clipping ratios in a CPA laser system for a variety of matched stretcher-compressor designs. Then we analyze the output pulse’s temporal distribution, and find that the temporal contrast ratio is mainly determined by the stretcher and the amplifier. The pulse duration of the output pulse is mainly influenced by the amplifier.

In this paper we propose a system with the piezoelectric actuator by the single neuron adaptive PID controller for the grating tiling. Then the design of the control system as well as the control method by considering the nonlinearity of piezoelectric actuators is discussed. At last, close loop position examinations by the capacitive displacement sensor with nanometer scale precision are performed. The experimental results indicate that the system is working effectively. The system is provided with the characters of self-learning, easy calculating and adaptability as well as of a simple structure.

The laser irradiation non-uniformity of target is required below 5% in inertial confinement fusion (ICF). The scheme of combining smoothing by spectral dispersion (SSD) and lens array (LA) is introduced to meet the above demand, based on the present application LA. The feasibility of the scheme is analyzed by numerical simulation. It shows that the irradiation non-uniformity of focal spot falls down from 14% with LA to 3% with SSD and LA. The result power spectrum analyses of focal spot show that the smoothing effect is caused by middle and high frequency intensity suppression. The scheme can improve the ability of beam smoothing. The results are useful for practical application.

A scheme of combining technology of lens array (LA) and smoothing by spectral dispersion (SSD) is introduced to improve the irradiation uniformity in laser fusion based on the earlier works on LA. The feasibility of the scheme is also analyzed by numerical simulation. It shows that a focal pattern with flat-top and sharp-edge profile could be obtained, and the irradiation nonuniformity can fall down from 14% with only LA to 3% with both SSD and LA. And this smoothing scheme is depended less on the incidence comparing to other smoothing methods. The preliminary experiment has demonstrated its effectiveness.

The field intensity distribution and phase velocity characteristics of a flat-top laser beam are analyzed and discussed. The dynamics of electron acceleration in this kind of beam are investigated using three-dimensional test particle simulations. Compared with the standard (i.e., TEM00 mode) Gaussian beam, a flat-top laser beam has a stronger longitudinal electric field and a larger diffraction angle. These characteristics make it easier for electrons to be trapped and accelerated by the beam. With a flat-top shape, the laser beam is also applicable to the acceleration of low energy electron and bunch compression.

The target irradiation uniformity is improved by using two-dimensional smoothing by spectral dispersion and a lens array (LA). A pattern of steep edges and good middle-scale uniformity is obtained with a diffraction-weakened lens array. When two-dimensional spectral dispersion is employed in the laser chain, the beams experience spectral dispersion in two vertical directions, and the fine stripes caused by beamlets interference are smoothed out greatly. If the effect of lateral thermal conduction smoothing is taken into account, the high spatial-frequency intensity fluctuation can be eliminated further. Two-dimensional theoretic results indicate that a flat-topped and steep-edged target pattern can be achieved in this scheme. Because the position of the target does not require adjustment with high precision, the implement of this scheme is comparatively convenient.

The noise origin of attenuation system is explored by analyzing the wedged plate attenuator based on Fresnel transmission through two pairs of wedged plates. Multiple reflections between two surfaces of a pair of wedged plates introduce fluctuating error into the attenuation of the wedged plate attenuator and wavefront distortion of the exit laser beam. The attenuation and the radial light intensity distribution of the laser beam considering the effect of multiple reflections are calculated when the wedge space varies. And the calculation results show that wedge space between a pair of wedged plates has important influence on laser beam quality. The fluctuation of attenuation decreases but the distortion of wave-front becomes more complicated with the wedge space between the two parallel surfaces of wedged plate pairs increasing.

A method for precisely measuring the phase retardation of wave plate is presented. In this method, a test wave plate is placed between a polarizer and an analyzer, with the polarizer and the analyzer being rotated to different position, the output power is tested and the phase retardation of the wave plate is reached. The modulated light source and the demodulation technique are used to erase the noises, which are helpless for continuous light, arise from background light and electronics. Since the light path is divided into measurement light path and reference light path and the software division technology is used, the influence of light fluctuation is eliminated and the phase retardation of wave plate can be measured precisely. Main error factors that degrade the measurement accuracy are analyzed in detail, which are wavelength change of the light source, temperature change of surrounding environment, oblique incidence of the light, rotational angle error of the sample carriers and fluctuation of the light power. Phase retardation errors that arise from the above mentioned factors for a piece of crystal quartz plate with thickness of 0.52 mm and phase retardation being 90° at 1064 nm are analyzed and calculated. The influence of light fluctuation is greatly improved after using division technique, and the total error is ±1.58°. The quartz wave plate with thickness of 0.52 mm is tested experimentally, and its phase retardation is 91.06°±1.78°, which consists with the theoretical analysis. Methods about measurement and error analysis can also be used for other wave plates.

Different from previous focusing on subwavelength imaging in the near field, we outline another potentially useful application of the self-collimating photonic crystal -- low-pass spatial filtering. A two-dimensional square-lattice photonic crystal is taken as an example and the low-pass spatial filtering is demonstrated by the dispersion analysis and numerical simulations. The high-spatial-frequency components, whose incident angles exceed a critical value, are reflected totally because no Bloch modes of the photonic crystal can be excited. However, the low-spatial-frequency components are coupled to the self-collimating modes and permeate the photonic crystal with high transmissivity.

As distinct from coated photonic crystals, in this paper we propose a novel one that is made of dielectric tubes arranged in a close-packet square lattice. Without metallic cores, this structure is low-loss and convenient to fabricate. A lefthanded frequency region is found in the second band by dispersion characteristic analysis. Without inactive modes for the transverse electric mode, negative refraction and subwavelength imaging are demonstrated by the finite-difference time-domain simulations with two symmetrical interfaces, i.e. ΓX and ΓM.

In this paper we theoretically investigate a photonic crystal with dielectric rods in a honeycomb lattice. Two left-handed frequency regions are found in the second and third photonic band by using the plane wave expansion method to analyze the photonic band structure and equifrequency contours. Subwavelength imaging by the photonic crystal flat lens are systematically studied by numerical simulations using the multiple scattering method. Different from the photonic crystals with noncircular dielectric rods in air, this structure is almost isotropic at the optimal frequency for superlensing. As a comparison, flat slab focusing is also demonstrated at other frequencies in the two left-handed regions.

Optical properties of a two-dimensional square-lattice photonic crystal are systematically investigated within the partial bandgap through anisotropic characteristics analysis and numerical simulation of field pattern. Using the plane-wave expansion method and Hellmann–Feynman theorem, the relationships between the incident and refracted angles for both phase and group velocities are calculated to analyze light propagation from air to photonic crystals. Three kinds of flat slab focusing are summarized and demonstrated by numerical simulations using the multiple scattering method.

Stable single-frequency and single-polarization distributed-feedback (DFB) fiber laser was realized by giving a pressure on the phase shift region of the fiber grating. The output wavelength of the DFB fiber laser is 1053 nm. When the pump power of 980nm laser diode is 100 and 254mW, the output power can reach 8.3 and 37.1mW and the polarization extinction ratio was 26 and 20 dB, respectively. After chopped by Acousto-optic modulator (0.3 Hz), the pulse peak value variance is 4.65%(peak to peak) and 1.098% (RMS) for 31 min.

Yb-doped phase-shifted fiber Bragg grating (PS-FBG) has been fabricated with phase shift introduced by shielded method. In the fabrication process, the PS-FBG is used as the laser cavity. Whether the introduced phase-shift is π/2 or not is determined by the laser output power. As long as the output power of the laser begins to drop down, the exposure is stopped, and the phase shift is π/2 then. It is necessary to anneal the PS-FBG to stabilize its characteristics, which will reduce the introduced phase-shift. The second exposure of the PS-FBG is needed to restore the π/2 phase shift. A fiber grating laser has been made with the method. When the pump power is 100 mW, the laser output is 25 mW with signal-noise-ratio (SNR) of 60 dB. Within 1 h the output fluctuation of the laser is less than 1%. The laser is always under single-mode operation when the temperature of the fiber grating is tuned between 25 ℃ and 30 ℃.

A diode-pumped Yb-doped double-clad fiber amplifier (YDDCFA) with the narrow bandwidth continuous wave (CW) and pulse input signal is investigated. The input single-mode (SM) signal bandwidth is 10^(-4) nm from a distributed feedback (DFB) fiber laser. The saturated gain of the CW amplification is 11 dB at the forward pump. And besides CW signals, we also amplify pulses with duration of 150 ns and the 1-Hz repetition. The pulse is amplified to 2 W of peak power, 0.31 microjoule of energy, 23 dB of gain and less than 6% of stability at the forward pump power of 1.4 W. For higher power, reflections and backscattering can generate the self pulsation in the amplifier. The results are important for the development of the narrow-band double-clad fiber amplifier.

By solving a set of time-dependent equations, the characteristics of the ytterbium-doped double-clad fiber amplifier are presented. Besides the steady state in the fiber of the upper-state population, pump power and amplified spontaneous emission without the input signal, the dynamic characteristics of the high power Gaussian pulse amplification like the evolution of pulse waveform distortion, upper-state population distribution and stored energy and pulse energy of the amplifier under the forward and backward pump, are simulated. The relations between the output pulse energy of the amplifier and the different input pulse peak power or pump power are also discussed. The models and results can provide important guide for the design and optimization of the high power pulse amplification.

Using three-dimensional test particle simulations, we investigated electrons accelerated by a focused flat-top laser beam at different intensities and flatness levels of the beam profile before focusing in vacuum. The results show that the presence of sidelobes around the main focal spot of the focused flat-top laser beam influences the optimum (as far as electron acceleration is concerned) initial momentum (and incident angle) of electrons for acceleration. The difference of initial conditions between laser beams with and without sidelobes becomes evident when the laser field is strong enough (a0>10, corresponding to intensities I>1×10^(20) W/cm2 for the laser wavelength λ=1 μm, where a0 is a dimensionless parameter measuring laser intensity). The difference becomes more pronounced at increasing a0. Because of the presence of sidelobes, there exist three typical CAS (capture and acceleration scenario) channels when a0≥30 (corresponding to I>1×10^(21) W/cm2 for λ=1 μm). The energy spread of the outgoing electrons is also discussed in detail.

Based on the rate equation, the amplification performance of small-mode-area (SMA) and large-mode-area (LMA) ytterbium-doped double-clad fiber amplifiers was studied using the finite-difference method. The Yb-doped double-clad fibers with the mode diameter 6.5 μm and 20 μm were used as the gain media for the amplification of narrow-band signals. Under the pump laser at the center wavelength of 915 nm, the relationships between output power and input signal power, pump power as well as fiber length, were discussed for SMA and LMA. Especially for LMA fiber amplifiers, it is important to choose the optimal fiber length. For the fiber amplifier with different mode diameters, the optimal pump power and fiber length were also analyzed. It is obtained that the critical pump power is about 4 W with the fiber length of 4 m, which is in accord with the experimental results. The results provide a theoretical guide to optimize fiber type and fiber length considering available signal and pump power, desired gain and mode requirement of fiber amplifiers.

Due to the demand of complicated-time-shape seed laser pulse for inertial confine fusion (ICF) research, by using the pulse-shaping system based on aperture-coupled striplines, we design the front-end laser pulse temporal waveform, which totally meets the requirement of physical experiments. Besides, we precisely calculate the numerical relationship between the voltage coupling coefficient of the aperture-coupling striplines and its aperture width with a new method. In order to meet the demand of high-contrast laser pulse waveform, we put forward a new scheme based on double-electrode integrated wave-guide modulator. The system is capable of providing 1～3 ns pulse envelope, high contrast (>100∶1) and slippery waveform, meeting the “ShenGuang Ⅱ” eight lines and the ninth facility demand of the front-end temporal shaping laser pulse.

We have investigated the basic properties of subwavelengthdiameter hollow optical fiber with exact solutions of Maxwell’s equations. The characteristics of modal field and waveguide dispersion have been studied. It shows that the subwavelength-diameter hollow optical fibers have interesting properties, such as enhanced evanescent field, local enhanced intensity in the hollow core and large waveguide dispersion that are very promising for many miniaturized high performance and novel photonic devices.

A theoretical method to analyze four-layer large flattened mode (LFM) fibers is presented. The influence of the second cladding on the properties of four-layer LFM fiber, including the fundamental and higher-order modal fields, effective area, bending loss, and dispersion, are studied by comparison. At the same time, the reasons for the different characteristics are considered. The obtained results indicate that the effective area of the four-layer LFM fiber is about 1.6 times larger than that of the conventional standard step-index fiber and the fibers have better bend-induced filtering ability than three-layer LFM fibers.

A flat high gain L-band gain-clamped erbium-doped fiber amplifier (GC-EDFA) by using backward C-band amplified spontaneous emission (ASE) is proposed. It uses two stages of EDFs pumped forward as gain media, and a broadband chirp fiber Bragg grating (CFBG) to reflect the backward C-band ASE back into the loop to control the gain, which avoids spectral-hole and relaxation oscillation due to no controlling laser exists. Compared with other similar GC-EDFAs, the proposed structure has higher and flatter clamped gain in L-band because of its optimal structure -- the length of EDFs and pump power, pump scheme, etc.. The gain is above 23 dB, the bandwidth of 3 dB is more than 36 nm, and the input signal saturation power arrives -15 dBm.

We propose a kind of photonic crystal fiber with flat-top fundamental mode by introducing a depressed central dip into the core of the conventional index-guiding photonic crystal fiber. The design guidelines and characteristics of the large flattened mode photonic crystal fiber (LFM-PCF) are discussed in detail. By appropriate design, the effective area of the LFM-PCF can be increased by a factor of greater than 2 as compared with conventional index-guiding photonic crystal fiber with the same hole and pitch parameters. The improved effective area, single mode operation and flat-top fundamental mode output make LFM-PCF an ideal candidate to realize high power, high beam quality fiber amplifiers and lasers.

The technique of Brillouin scattering distributed optical fiber sensing has been presented. Optical heterodyne detection was used to detect the weak Brillouin back scattering signal based on single longitudinal mode distributed feedback (DFB) laser and electric optical modulation technique. The scattering signal was amplified effectively by improving the filter and erbium doped fiber amplifier (EDFA). The 11 GHz radio-frequency (RF) signal of Brillouin back scattering is gathered and averaged. The experimental procedures and results are presented. The results show that the peak power of Brillouin back scattering at 11 GHz can reach 50 mV, and the intensity noise of light source induced the system's signal to noise ratio (SNR) decreased greatly, which reduced the difficulty of signal process in demodulation system. The experimental results confirm that the configuration is feasible.

According to the laser conditions of the ninth beam of Shenguang-Ⅱ facility,the characteristics of the laser-driving shockwave propagation in Al-Au impedance-matching target were studied by JB code and multi-step technique,respectively.The experimental results were consistent with the numerical simulation results.The results show that the shockwave's maximum stable propagation distance in gold decreases rapidly when shock front propagates from aluminum to gold.Therefore,when people design the Al-Au impedance-matching target, they should first select the Au step thickness, in which the shockwave should propagate steadily. The Al step thickness will be selected according to the calculated shockwave velocity raio of the two materials in impedance-matching target. For the ninth beam of Shenguang-II facility, the suitable Al substrate thickness is about 30 μm, the Au step thickness and the Al step thickness should be selected as less than 10 μm and 17 μm, respectively.

Experimental laboratory studies on the equation of state (EOS) based on laser driven shock waves has become a major way to obtain EOS data for materials above TPa pressures. Recent progress in laser EOS research is presented, with emphasis on the characteristics of laser driven shock waves, measurement methods in laser EOS experiments, research on shock wave planarity, stability and cleanliness, and the experimental results of such research.

Laser driven shock wave stability of propagation in impedance match target was studied using one dimension characteristic line method.In addition，one dimension three temperature laser-target coupling JB program was used to simulate it.It was compared with simplified equation of state.The results of the two methods agree wel1.The calculation results show that shock wave stability of propagation in Au depends closely on the thickness of the A1 base.

A key problem in streak camera data processing is how to determine the position of the signal pulse，and the resuits will be effected by the signal to noise ratio(SNR)of the experimental data and the signal pulse position determination method.In the paper，FW HM (half maximum and half width)method is used to determine the single pulse position.The method could determine the signal pulse po sition with sub-pixel precision when the SNR more than 100:1. As for the data with bad signal to noise ratio(SNR less than 10:1)，a Fast Fourier Transform method is used to filter the noise first，then the pulse position is determined by the FW HM method.And the streak camera calibration data of the super-fast sweep rate was processed.The sweep speed is(0.214+0.0029)ps/pixe1.The linear dependent coefficient is 0.9997, which shows the streak camera scanning linearity is good.

This paper describes the elliptical crystal spectrograph(ECS)which is used to investigate X-ray spectroscopy of laser-produced plasmas.The spectrometer was calibrated for experiments on“Shenguang lI”X laser target chamber.The K-shell and M-shell emission lines of laser-produced plasma were measured by the space-resolved spectrometer.Some X-ray spectral lines were obtained through studying and classifying photographs of spectra recorded by X-ray CCD camera. The measured spectral resolution of spectrograph was given.The focusing spectrometer based on the ECS provides high spectral resolution and spatial reso1ution as well as high luminosity(high collection efficiency).Possible applications of the ECS are demonstrated.

Equation of state (EOS) experiments were performed using a double-frequency (2ω) laser pulse, which exported from the ninth beam of “SG-Ⅱ” laser facility. The ninth laser beam was smoothed by lens-array (LA) uniform illumination technique to generate a flat-top intensity distribution at the target plane and planar shock fronts in targets, which was validated by the plane-target experiments. The shockwave stabilities were experimentally measured by the multi-step target technique. The results showed that the shocks were steady enough during the target thickness range in which the shock velocity was measured. Also, the results were consistent with the numerical simulation results. On this base, the Au EOS was measured by using the impedance-matching technique. Shock pressure higher than 2.7 TPa was achieved in Au, and the relative expanded uncertainties of the measured shockwave velocity were 2% (K=2). Moreover, the experimental data were compared with existing experimental data and EOS models.

The sol-ge1 organicmodified silica(SiO2:(CH3)2SiO=1:1)moisture-resistant(MR)and porous silicaantireflective (AIR)coatings were studied and developed for laser phosphate glasses in the national high laser systems.The stability of viscosity of MR coa ting solution an d AR colloidal suspension was researched .The surface reflection of coated phosphate glasses decre~ses 6.5％-7.5％.The laser damage threshold of coatings was 12 J/cm2，1 053 nm/1 ns.The coatings roughness(RMS) was 2.523 nm.

A new testing system was developed for the instantaneous parameter of multiple pulses of Xe flashlamps discharge system, which can replace the traditional testing mode of manifold paths oscillograph. It had a powerful function and was easy to operate, directly perceived through the sense, resisted disturb. It had a enormous data bank for looking for to all computers of a network.

Controlling the wavefront distortion introduced by mechanical mounting to raise the quality of output beam in inertial confinement fusion (ICF) facility must be considered in the structure design of the large aperture Nd:glass main amplifier. A novel method of data processing between the finite element deformation results and the surface distortion of optical element was presented and compared with the traditional method. The support system of large octagonal Nd:glass is optimized with integrated optomechanical analysis method based on the new data processing interface. The transmission wavefront distortion introduced by optimal support system is less than tenth wavelength and the correlation between the wavefront distortion and the design parameters variation is little.

For special requests of eliminatng noise in wrapped phase field, a vector filtering method of wrapped phase field pretreatment is proposed. Power spectral density and the filtering behavior of vector transformation are analyzed theoretically. Through simulation, the size of the filter template affecting on filtering imaging is investigated, the filtering effects of second mean filtering method and vector filtering method at the same size of filter template is comparised, the curve distribution of power spectral density of second mean filtering method and vector filtering method is analyzed. It shows the phase image filtered by vector filtering method which can decrease noise is still clean, the distribution of power spectral density has no change, the spectral information loss after pretreatment though vector filtering was smaller than second mean filtering. The vector filtering method improves signal-to-noise ratio, furthermore the information integrity still obtains a better guarantee at the same time.

Mode matching of the pump beam with laser modes in laser diode (LD) end-pumped solid-state laser was experimentally studied. Considering both the mode-match degree and laser threshold, the effective absorbed pump power in Nd:YAG was calculated. Based on the criteria, a 946-nm laser resonant cavity was designed and a 473-nm blue-light solid-state laser was efficiently assembled by means of intracavity frequency doubling.

The asymmetry of a-cut Nd∶YVO4 leads to asymmetrical laser output from laser diode (LD) end-pumped Nd∶YVO4 solid state laser, which differs from Nd∶YAG laser. The finite element was applied to analyze the thermal effect of LD end-pumped a-cut Nd∶YVO4 crystal, including temperature distribution, internal stress and its deformation. The results indicate that the thermal lens of end-pumped a-cut Nd∶YVO4 crystal takes the ellipsoidal distribution. The method of balancing the asymmetry of thermal lens was put forward by the way of structure and pumping, and experimentally proved feasible.

A stable and efficient all solid-state green laser with average power over 30 W is studied. The phase mismatching and thermal lens effect induced by local temperature rise of doubling frequency crystal are the major reasons affecting frequency doubling efficiency and laser output power stability. The method of grads-compensating temperature controll is used to adjust the operating temperature of frequency doubling crystal with large size. This temperature control system debases the inside and outside temperature grads of crystal to compensate the phase mismatching and thermal lens effect of frequency doubling crystal. This laser that is side-pumped by three bars laser diode array of 60 W and adopts the high efficiency flat-concave cavity, intracavity frequency doubling resonance structure, and acoust-optic Q-switching generates a maximum green average power of 31.6 W with 110 ns pulse width and 10 kHz repetition rate when pumped current of laser diode was 25 A and pumped power was 174.6 W. The optic-optic transition efficiency is up to 18.1%, and power stability is up to ±0.66% with beam quality factor of green laser M2=4.3.

The solid state heat capacity laser (SSHCL), as one of the most important high-power solid-state lasers, has attracted extensive attention. Numerical simulation of temperature and stress distributions of laser crystal slab in the heat capacity operation mode is a major means to understand the specific property of the laser. Using the method of plane stress approximation, the two-dimensional (2D) mathematical formulas that describe the temperature and stress distributions of laser diode (LD) pumped heat capacity slab laser are derived. Then the absorbed pump power density, 2D distributions of temperature and index of refraction are also analyzed and discussed. According to the results, the 2D distributions of temperature and stress are more homogeneous than that of the one-dimensional distributions.

In order to realize the third harmonic propagating at high-power and irradiating target, a method based on the combination of wedge window and focus lens has been proposed to serve the important function of angularly dispersing the unconverted the fundamental and second harmonic away from the third harmonic target in high power laser facility. Based on the multifunctional and high-power laser system of “Shenguang-Ⅱ” facility, the wedge window is designed. And resulted from the wedge window, the B-integral and the space error between the second harmonic and third harmonic are analyzed. In experiment, the third harmonic propagating at high-power has been improved from 0.7～1 J/cm2 to 2.8 J/cm2, and the space is up to 2.85 mm at the third harmonic target. The method can be used to achieve the third harmonic splitter in high power laser facility.