Due to group velocity mismatch, the generation of the cascaded fifth-order nonlinear phase shifts with femtosecond pulse will inevitably cause the severe pulse distortion. By theoretical study and numerical simulations, we show that undistorted femtosecond pulse which is impressed the cascaded fifth-order nonlinear phase shifts can be obtained at large values of the phase mismatching kL.

A high power laser system delivering a 20-TW, 0.5 - 0.8 ps ultra-short laser pulse and a 20-J, 500-ps long pulse simultaneously in one shot is completed. This two-beam laser operates at the wavelength of 1053 nm and uses Nd doped glass as the gain media of the main amplification chain. The chirped-pulse amplification (CPA) technology is used to compress the stretched laser pulse. After compression, the ultrashort laser pulse is measured: energy above 16.0 J, S/N contrast ratio ~ 10^(5) : 1, filling factor ~>52.7%. Another long pulse beam is a non-compressed chirped laser pulse, which is measured: energy ~ 20 J, pulse duration 500 ps. The two beams are directed onto the target surface at an angle of 15°.

Nd∶doped-glass-based sub-picosecond laser system with the maximum peak power of greater than 20 tara watts and the energy on target surface of 16 J is accomplished by using the chirped laser pulse amplification technology. While the laser pulse is focused by an off-axis parabolic mirror, the power density on target surface of approximately 2×10 18 W/cm 2 is acquired. In the performed neutron experiment, a C 8D 8 plate target is placed on the focal spot of the off-axis parabolic mirror. The maximum neutron yield for a single shot reaches 2.4×10 4. Still some other related problems are discussed

With the aim of achieving the power balance of “SHENGUANG Ⅱ”, the innovative project of the main array amplifier with the angular variable mirror is studied. The first engineering research results of the new project which were attained on “SHENGUANG Ⅱ” are reported in this paper, including the project design essentials, the outcome of the performance measurement and check in- line, and the result of general energy balance experiment.

Owing to the PTD effect in the lenses of spatial filter, large temporal front distortion of femtosecond pulses occurs in the spatial filter. In this work, in order to design a spatial filter which is applicable to high power femtosecond laser system, PTD of achromatic doublet or separated doublet is calculated and special spatial filter is discussed in which achromatic doublet or separated doublet replace the single lens. PTD of the special spatial filter is little so temporal front distortion of femtosecond pulse in laser system is eliminated or reduced.

A LDA pumped Nd:YLF regenerative amplifier has been developed, which works at wavelength of 1053 nm and repetition rate of 1 Hz. It can produce laser pulses of 2 mJ energy, 4ns width and base transverse mode TEM 00 . Total gain of 1×10 7 is reached, and pulse to pulse energy fluctuation didn′t exceed ±4 7% (peak). Experiment setup and detailed results are presented in this paper.

The working principle of double cascade connected or parallel connected electro-optics deflectors used in the temporal-spatial transformation instrument is introduced and the ability to produce shaping laser pulse of it is theoretically analyzed. The laser pulse shaping experiment with double cascade connected or parallel connected electro-optics deflectors is performed. The result conform to the theoretical analysis which proved that the ability to obtain shaping laser pulse is improved greatly with a double cascade connected electro-optics deflectors.

Laser pulse is quickly deflected by LiNbO3 electro-optics deflector which is driven by avalanche transistor pile, thus a stable laser pulse output ( the pulse width is ns in scale) is gained, the instability of which is decreased from 10%(RMS) to 4%(RMS)compared with the single-longitudinal-mode Q-switched laser pulse output of the oscillator. It indicates that the amplitude stability of shaping laser pulse is improved greatly.

A Yb doped phase shifted Fiber Bragg Grating fabricated with double exposure method was reported in this paper.In the experiments, a weak peak was found in phase shifted FBG, and the phenomenon was explained.

An approximative λ/4 -shifted DFB Yb-doped fiber laser was made in the length of 10 cm Yb-doped fiber by double exposure method. Then, it was treated with λ/4-shifted Yb-doped DFB fiber laser with UV trimming. The running characteristic of the laser with scaning F-P interferometer and oscilloscope was observated. SLM Yb-doped λ/4-shifted DFB fiber laser was obtained. The threshold is 20 mW. When pump power was 130 mW. 25 mW SLM laser at 1053 nm was got.

The π phase shifted distributed feedback fiber lasers, in which the power would focus on the phase shift region if the coupling strength is high enough, is often used to acquire single frequency output. But due to the spatial hole burning,the output wavelength would be different for the two output ports. The fundamental mode focuses on the port near the phase shift region while the ±1 modes would focus on the other port if the phase shift region is far away from the center of the grating. Both the theoretical analysis and experiments are presented.

It was found that the output power of the distributed feedback fiber lasers would be improved after annealing or left unused for several days after the laser had been fabricated, and the output of the fundamental mode would not increase but be clamped while the ±1 order modes would be predominant with the enhancement of the coupling coefficient during the fabrication. The paper discussed the influence of UV-induced fiber loss on the fiber phase-shifted DFB lasers. Due to the gain saturation and fiber internal loss, which included the temperament loss and permanent loss, there was an optimum coupling coefficient for the DFB fiber lasers that the higher internal fiber loss corresponded to the lower optimum values of coupling coefficient.

Starting from the Maxwell's equation, and using the resonant-dipole equation together with the multilevel rate equations which take the effects of energy relaxation into consideration, we have derived a more realistic numerical model of the chirped pulse amplification for an ultra-broad band width laser amplifier. Numerical simulations of this model show that both the intensity profile and the energy fluence of the amplified chirped pulse are closely connected with the two relaxation effects: the relaxation of the thermalization among the components of the laser multiplets and the depletion of the lower laser level. The results are valuable for the design of ultra-broad bandwidth chirped pulse amplification lasers.

On the basis of the threebeam output of basic frequency from "ShenguangII" laser facility and beam smoothing technology of lensarray, the shock wave with a better planarity in ranged 650～750μm the target was created after optimum design and rational combination for laser beam. Then the efficiency of output beams from "ShenguangII" laser facility had been raised. And the shock stability experiment with the inclinedplane target indicated that the shock wave steadily propagated in the Al target of thickness of about 28.38～55.82 μm and 22.13～35.07 μm under the power density of 3.26×1014 W/cm2 and 3.11×1014 W/cm2 respectively.

Being aimed at the condition with ultra nonuniform of near field distribution from "Shenguang Ⅱ" (with none laser intensity in large area), by use of the uniform technique of lens array and by the optimizing design for the system combined with principal focal lens and small lens array, a large spot uniform irradiation on target surface has been realized, also a shock illuminant signal with good planarity in large region is obtained while it drives an aluminium plane target.

With the folding target and double-step target,the propagating character of shock wave driven by an inclined-incident (with angle of ～45°) laser was studied on “Shenguang-Ⅱ” high-power laser facility.The result indicated that the shock wave in the target still propagates along the vertical direction to the target surface.Also the same result was verified indirectly by another experiment based on the measurement for spatial intensity distribution of x-ray radiated from jet plasmas.