By employing a simple model of describing three-level lasers, we have theoretically investigated the effect of photon lifetime on the output dynamics of Er-doped distributed feedback fibre lasers. And based on the theoretical analysis we have proposed a promising method to suppress self-pulsing behaviour in the fibre lasers.

The impact of the stretcher on the contrast ratio of the out pulse is analyzed making use of the ray -tracing method , which is based on the contrast ratio model of chirped pulse.When the beam size in the stretcher is increased from 2 mm to 40 mm ,the contrast of the output pulse approximately increase two magnitude. When the input pulse is Sech2 ,the contrast of the output pulse is better than what the input pulse is Gassian or Rectangular.

Beam automatic alibnment system is used to implement beam adjustment .Basing on the principle of matrix optic，the mathematical model for auto-alignment in four-pass amplifier is built by analyzing the properties of this system. Using this model, the shems of beam alignment is designed and the analytical solutions of the amounts of near field adjustment and far field adjustment are obtained, respectively.

ZrO2 sol was prepared by controlling hydrolysis ZrOCl2·8H2O in heated alcoholic solution. The thin films were deposited by dip technique. The characterization of ZrO2 sol was analyzed by viscosity, particle size analyzer, IR, DSC and AFM analysis. The results showed that the average size of sol particles was 18.9 nm; the refractive index of coatings treated at 300℃ was 1.95; the morphology of coatings surface was smooth, and its average roughness was only 0.561 nm. The laser induced damage threshold of ZrO2 coating was 14 J/cm2(1064 nm, 1 ns)

Characteristics of X-ray and spout direction of heat plasma flow were studied on Shenguang-II laser facility. Using of pinhole X-ray camera, X-ray photons from the plasma of aluminum(Al) irradiated by 1.053 μm laser, was measured and analysed. It is observed that the spatial distribution of X-ray photons in Al plasma for tilted irradiation is symmetic at the center of the target. The spout direction of heat plasma flow is inferred by the distribution contour of X-ray photons. The experimental results show that the spout direction of heat plasma flow is normal to target plane and the output intensity of X-ray photons does not increase significantly for tilted laser incidence. Uniformity of laser energy depositions improved by superposing tilted incident and laser perpendicularly incident laser. At the same time, it is found that the conversion efficiency from the tilted incident laser energy to X-ray photons of laser-produced plasma is decreased

The Al, Cu and Au thin foils were rolled with the precision rolling mill, and the metal foils were fabricated as impedance match targets used in the laser equation of state experiments by the assembly. The target parameters were measured by a-step500 and NT1100. The fabricated impedance match targets were used in "SGII". Good images were obtained in experiment.

The fabrication and measurement of isentropic release targets were described. The Al，Au，Ag、Cu and Zn thin foils were cut to hundred micron by apparatus of laser. They are fabricated to isentropic release targets using in the laser equation of state experiments by the assembly. The parameters of targets were measured by NT1100 profiling system. The isentropic release targets were used in "SG II" experiments and good images were obtained.

The supersonic jets and the interaction of strong shock waves are ubiquitous features of the nonlinear hydrodynamics of inertial-confinement fusion, astrophysic, and related fields of high energy-density science, so very important value have their studies in laboratory. A laboratories experimental study on jets is reported. The plasma jets were created by an ns laser pulse irradiating a special circular hole target, and the shadow of jets were recorded by using an X-ray laser probe with wavelength of 13.9 nm. Legible shadow images of plasma jets were obtained. The experimental results and theoretical simulation were in qualitative agreement.

Based on the optical activity of quartz crystal, we proposed a scheme for shaping the spatial intensity distribution of a linearly polarized laser beam by utilizing a quartz crystal plano-convex lens in combination with a polarizer. The intensity profile of the shaped laser beam can be easily switched from one profile to another by controlling the polarization direction of the incident laser beam.

A new spectrum shaping method, based on electro-optic modulation, to alleviate gain narrowing in chirped pulse amplification (CPA) system, is described and numerically simulated. Near-Fourier transform-limited seed laser pulse is chirped linearly through optical stretcher. Then the chirped laser pulse is coupled into integrated waveguide electro-optic modulator driven by an aperture-coupled-stripline (ACSL) electrical-waveform generator, and the pulse shape and amplitude are shaped in time domain. Because of the direct relationship between frequency interval and time interval of the linearly chirped pulse, the laser pulse spectrum is shaped correspondingly. Spectrum-shaping examples are modeled numerically to determine the spectral resolution of this technique. The phase error introduced in this method is also discussed.

In order to improve the energy efficiency of the inertial confined fusion (ICF) high-power laser system and use the optical energy sufficiently, it is necessary to convert Gaussian laser beam into uniform beam, or into parabolic-like beam to precompensate the spatially dependent gain of the Nd∶glass amplifiers, for the sake of uniform output distribution at the target. The intensity control is obtained with panels composed of binary pixelated arrays of metal pixels, which was designed by error diffusion method. The shaping effect is numerically simulated. The factors, which will influence the shaping effect, such as mismachining of the panel and size of the pinhole of the spatial filter are discussed. An anti-gaussian distribution and a parabolic distribution binary panels are fabricated. The experimental shaping result is given and the error is analyzed. Binary panels are proved to be excellent shaping elements in modeling the intensity of laser.

In the design of the Offner stretcher, it is very important to investigate the mirror curvature radius errors, which has a direct impact on the quality of the output pulse. So it is necessary to analyse the effect on the output pulse contrast due to the mirror curvature radius manufacture errors in the ffner stretcher. A ray-tracing model for ffner stretcher with these errors is established. Based on the model, effects on output pulse contrast through the stretcher is analyzed.When the mirror curvature radius error is between 0.2%～0.5%, it can fully meet the requirements for the SHENGUANG Ⅱ petawatt laser facility. Also, when there is error for the mirror curvature radius, keeping the distance between concave mirror and convex mirror half of curvature radius of the concave mirror is better than keeping the two curve mirrors in the same center.

The stretcher system is an important part in the high-engery petawatt laser facility. The stretcher system design has a direct impact on the quality of the output pulses. The stretcher systems in some famous high-energy petawatt laser facility are summarized. And the structure and parameters are compared and discussed.

Four-zone method to measure the phase retardation of wave plate is put forward based on the polarizer-wave plate-analyzer system. Four sets of light intensity were collected by adjusting azimuth angles of measured wave plate and analyzer. The phase retardation of the wave plate is figured out with linear calculation. This method eliminates the error caused by polarizer and analyzer imperfections completely in phase retardation measurement. No standard wave plate or other phase modulation instruments are necessary in the system. The measured wavelength range is extended, because it is only related to polarizing prisms and detectors. With this measuring system, the instrument error σ is less than±3.49065×10-3 rad (about 0.2°). The accuracy is increased by about one order of magnitude compared with other algorithms which is verified by experiments.

Pinhole-assisted point projection (PAPP) backlight scheme is a newly developed diagnostic technique for laser-plasma experiments in foreign laboratories, which will play an important role in diagnostic experiments of inertial confinement fusion (ICF) physics. Experiments have been carried out on the additional beam of “Shenguang-Ⅱ” laser facility, to test the practicability of PAPP scheme. The K-shell X rays (～4.7 keV) emitted from laser-produced planar Ti targets pass through the pinhole aperture with diameter of 10～40 μm, then cast the shadow of the Au sample on CCD. Time-integrated two-dimensional (2D) pictures of the samples are obtained in the experiments with the resolution better than 16.1 μm. The merits, such as high resolution, large field-of-view, high contrast, have been found in the experimental results, and PAPP will become one of the most important diagnostic methods for Rayleigh-Taylor instability research, equation of state (EOS) research and so on.

The elliptical bent crystal spectrometer (EBCS) is coupled to X-ray CCD, and a set of system called focusing spectrometer has been developed. Optimization calculation indicates that the EBCS will allow a large measuring spectral range (0.133～0.756 nm) with crystals of practical dimensions and for a working distance of 981.56 mm to the source and have a spectral resolving power (λ/Δλ) better than 1000 as well as high signal-noise-ratio. X-ray spectrum from the laser-produced plasma has first been measured by the EBCS in the “ShenGuang Ⅱ” Facility. Some ion-like spectral lines were identified and classified. The measured energy resolution of spectrograph was also given. Such emission of resonance line, satellite line inter-combination line of like ions, and Lyman alpha line is useful for establishing the spatial distribution of electron temperature and ions density maps.

A scheme of high-accuracy time-synchronization between a shaped optical pulse and a probe optical pulse has been developed and used in the Shenguang Ⅱ facility. In this scheme, the probe optical pulse is firstly photoelectrically converted by the Si photoconductive switch and then used to trigger the laser pulse-shaping subsystem, so that laser pulse-shaping subsystem produces a shaped optical pulse synchronized with the probe optical pulse. In order to decrease time jitter induced by amplitude fluctuation of the triggering signal, the probe optical pulse is amplified to adjust amplitude of the triggering signal before photoelectric conversion. The synchronization root-mean-error less than 4.5 ps between the two pulses has been achieved with this scheme.

A highly stable, laser diode (LD)-pumped, all-solid-state Nd:YLF regenerative amplifier applied to amplify a nanosecond laser pulse is designed and realized. The maximum output energy and the best stability of the regenerative amplifier can be obtained when it operates in a saturated mode for all pulse duration and temporal profiles. In addition to the excellent stability, the output laser pulse fluctuation caused by the injected pulse energy fluctuation is inhibited. Extra post-pulse can decrease the temporal pulse profile distortion caused by the gain saturation effect. When the regenerative amplifier is seeded with a 240 pJ, 3 ns optical pulse, output energy of 4.2 mJ with an overall energy gain more than 107 and output energy unstability better than 1% (root-mean-square) are obtained. When an extra post-pulse with amplitude of 0.75 times of the seed pulse is added for a 3 ns optical square seed pulse, the square-pulse distortion is decreased from 1.33 to 1.17.

It is important to keep away from the ghost reflection point for the arrangement design of final optics assembly (FOA) in the high power laser facility. The high power output of the “SG-Ⅱ” upgrading laser, limited target field space and complicated ghost reflection distribution lead to the difficult design of the FOA. By using the ghost image analysis software designed by ourselves, we analyzed the ghost reflection distribution of the FOA. Then, the arrangement of two types of designs for the FOA was optimized. According to the characteristics of “SG-Ⅱ” upgrading laser, we obtained the design for the FOA, which can satisfy the system requirement exactly.

In a stretcher,it is important of spectral clipping. It has a direct impact on the quality of the output pulse. Base on the ray-tracing,an analytical spectral clipping model is present in the ffner stretcher . When the stretcher parameters is determined, the location of the grating placed has a very important influence on the pulse spectral clipping. When the grating placed on the symmetric center about optical axis, the spectral distribution through stretcher will be asymmetric about center wavelength of the laser, that is to say,the spectral clipping will be asymmetric spectral clipping.Therefore,the output pulse contrast will be droped approximately one magnitude in the SGII ninth beam petawatt upgrade laser facility. In order to keeping the spectral symmetry distribution about center wavelength of the laser through the stretcher, the grating must be placed on the asymmetrical position about optical axis.

Pivotal parameters and restricted condition of the grating-size-limited compressor in an ultra-short, ultra-intense laser system are analyzed, and three basic parameters are obtained. An optimal method for compressor to output a maximal pulse energy is developed, and the maximal output pulse energy of the grating-size-limited compressor is given. Compared with the traditional circular beam method, an advanced elliptical beam method is presented, which could be used to output much higher pulse energy, a smaller spot size and a larger focal intensity. Using numerical simulation, the maximal output pulse energy of the 500 mm grating compressor based on the circular beam and the elliptical beam are calculated separately. The results show that the 500 fs, 500 J, 1 PW pulse can be obtained without using tiled grating technology if elliptical beam method is used.

With typeⅡphase matching, a detailed description of second-harmonic generation (SHG) for ultrabroad-band pulse was presented. The phase errors induced by noncollinear phase matching, phase mismatch and group-velocity mismatch for ultrabroad-band pulse were analyzed. The results show that it is necessary to multiply a modulation function for the recorded interferometric intensity to avoid the effect of pulses bandwidth. The phase error generated by bandwidth is proportional to the nonlinear crystal length and the beams intersect angle. The phase error generated by phase mismatch and group-velocity mismatch is relatively large with type Ⅱ phase matching. The intensity and phase errors in the reconstructed pulses should be compensated.

Gain medium of modern high-average-power solid-state lasers can produce distortion for the reason of thermal effect, such as YAG. Wavefront distortion and depolarization often occur simutaneously. The thermal stress of the high-power solid state laser slab is becoming a serious problem for hindering the further power increasing of the laser. A method for calculating the thermally induced refraction index in a pumped heat capacity slab laser was studied. In this method, the fourth-rank piezo-optics tensors of YAG crystal were transformed from the crystal lattice coordinate system to the laboratory coordinate system. With these new tensors, the thermally induced stress birefringence in a solid-state laser can be analyzed easily for any stress distribution. Furthermore, the calculations show that the birefringence in a zigzag slab depends on the angle under which the slab is cut from the boule. A theoretical description of the thermal and stress characteristics of heat capacity slab laser in two dimensional was also presented.