[en] A energy balance method of preamplifier system (PSA) is given based on the PSA in SG-Ⅲ facility. The preamplifier system has realized precise control of output energy by employing the method. The results of running of the facility show that the control precision of output energy of PSA is 5.47%. Furthermore, the influence factors of output energy fluctuation of PSA are quantitatively analyzed. The analytical results show that the primary influence factor of output energy fluctuation of PSA is the instability of 1 Hz pulse energy, and the key of enhancing the stability of 1 Hz pulse energy is to control the polarized energy fluctuation of the front-end seed. (authors)

[en] In the SG-Ⅲ prototype laser facility, if the laser's narrow bandwidth is adjusted to broadband while maintaining the main configuration, the energy output will decrease. This article evaluates the kilojoule energy output capability of tens-nm broadband laser, using numerical simulation softwares SG99 and CPAP respectively for narrowband and broadband laser propagation and amplification, and the program of one-dimension reverse propagation and amplification. The result shows the growing of gain-narrowing effect under broadband condition. The compensation of gain-narrowing is studied. With compensation, while losing 40% of the input energy, the output energy can reach 2000∼3000 J under 3 J injection. Hence there should be at least 5 J energy output after the preamplifier. This research will conduct the implementation plans for tens-nm broadband 2ω laser system. (authors)

[en] Quasi regenerative amplifier is put forward, which is based on the improvement upon the regenerative amplifier. In the amplifying system, the large-aperture amplifiers are used and the beam is imaged in the amplifier to keep the shape of the beam in the course of amplifying. Experiments on the feasibility of this amplifying concept show that this kind of amplifying system even based on low-gain amplifiers can achieve high system gain and can output high-energy pulses. (authors)

[en] With many advantages, scientific-grade CCD camera has been applied to diagnose the quality of laser beam in the field of high-power solid laser. Linear dynamic range is one of the most important characteristics. A new method calibrating the dynamic range for CAS-512A CCD system with optical wedge is reported

[en] The non-linear 2nd-harmonic conversion effect of the KDP crystal is researched and its effect to measurement accuracy of the laser pulse width. Experimental results show that: in condition of small signal and Gaussian beams, the 1st-harmonic laser pulse width is √2 times of that of the 2nd-harmonic one with type II KDP crystal whose thickness is 1-3 cm; Due to the non-Gaussian beams, the half-width of the 1st-harmonic pulse equals to the quarter width of the 2nd-harmonic pulse. With higher power density and energy conversion efficiency, the rate between the 1st-harmonic pulse width and the 2nd-harmonic one vary seriously

[en] A method for etalon design is reported, which is used for the calibration for sweep nonlinearity of streak camera and the test of its dynamic range with appropriate etalon, and the method of intensity correction dot by dot, the sweep nonlinearity of C1587 streak camera has been calibrated and automatically corrected by computer

[en] With the combination of CCD imaging unit and traditional multi-image camera to measure far-field distribution of laser output, the reconstruction algorithm for focal spot of high-power-solid-state laser output was described. The geometric cores of these focal spots was abstracted to center these spots by virtue of edge computational kernel applied in the field of image processing, nesting algorithm for focal spot reconstruction is put forward. It can precisely center these spots even if they are saturated partially and instantly reconstruct original focal spot, which makes it feasible to provide real-time data for laser control

[en] By comparing and analyzing various frequency conversion schemes, a compatible harmonic generation system has been designed. With type-Ⅱ-type-Ⅱ crystal combination configuration, polarization mismatch third harmonic generation and type-Ⅱ orthogonal quadrate second harmonic generation can be quickly switched. The thicknesses were optimized to be 10 mm for both crystals by numerical simulation method, as a result, the requirements of high efficiency for long pulse with low intensity, as well as high stability for short pulse with high intensity, can be satisfied. (authors)

[en] Experimental study of characteristics of laser induced damage on the K9 glass surface, irradiated by Nd:YAG laser operating at 1.064 μm wavelength and approximately 10 ns pulse duration and 1 Hz repetition rate, have been made. The change law of laser pulse output energy versus the repeat number of laser shots was investigated. Stereo microscope was employed to observe laser induced damage morphology after single-shot and multi-shot laser irradiation. The ripple damage on the K9 glass surface could be obviously observed, and the failure surface can be divided into three parts: ablation zone, microcrack zone and brittle fracture zone. After the first shot small damage spots appeared on the K9 glass surface; after multi-shot irradiation, micro-cracks and damage area increased gradually with the number of shots. Based on the laser-supported detonation wave theory, the interaction of high-intensity laser with K9 glass can induce a lot of microcracks in brittle material. Accumulation of multi-shot laser induced damage in K9 glass is obvious, the laser induced damage threshold of K9 glass surface is distinctly reduced, and the growing of microcrack zone and damage area are remarkable. (authors)

[en] In this paper we propose an efficient off-axis multi-pass Nd:glass amplifier with a birefringence crystal. By utilizing the optical principle of birefringence crystals and the angle differences of the input–output laser directions in a typical off-axis amplifier, the amplification-pass was extended from four-pass to eight-pass without increasing the off-axis angle. The detailed principles and amplifier parameter design are presented. Using the proposed off-axis eight-pass amplifier, a 1 Hz repetitive Nd:glass amplifier at several joules was experimentally demonstrated. A total transmission of 54% was achieved. At an input energy of 1.5 mJ and small-signal gain of 3.6, the output energy and the corresponding net gain were 2.5 J and 1667, respectively. The beam quality was good. The spatial intensity modulation index for 90% beam aperture was 1.29 and the 95% energy concentration of far field patterns was 2.77 times the diffraction limit. (paper)