Wavefront distortion is an important limiting factor for improving the output performance of high-power laser devices. It is an effective way to control the wavefront distortion via adaptive optics (AO) wavefront control technology. In the present paper, the research of wavefront control technology based on laser device is carried out, along with the feasibility and effectiveness of wavefront control technology are also verified. The functionality and reliability of major hardware components, such as the high-voltage power supply modules, the communication modules and the piezoelectric drivers, have all passed the offline test. The online test results show that the wavefront distortions for each of eight beam lines in the laser device has been corrected by the deformable mirrors installed in the main amplifier and the final optical assembly (FOA). Focal spot measurement shows a significant improvement in the focusing performance, with 95% of the frequency-tripled laser energy encircled in 30 times diffraction limit (DL). It is proved that the wavefront control technology can degread wavefront distortion generated from laser translating, and ensure a smooth beam transmission and a high output beam quality for the high-power laser devices.
KEYWORDS: Wavefronts, Adaptive optics, Digital signal processing, Control systems, Image processing, Adaptive control, Image transmission, Process control
Adaptive optics is a real-time compensation technique using high speed support system for wavefront errors caused by atmospheric turbulence. However, the randomness and instantaneity of atmospheric changing introduce great difficulties to the design of adaptive optical systems. A large number of complex real-time operations lead to large delay, which is an insurmountable problem. To solve this problem, hardware operation and parallel processing strategy are proposed, and a high-speed adaptive optical control system based on DSP is developed. The hardware counter is used to check the system. The results show that the system can complete a closed loop control in 7.1ms, and improve the controlling bandwidth of the adaptive optical system. Using this system, the wavefront measurement and closed loop experiment are carried out, and obtain the good results.
The shooting accuracy of cluster laser is an important indicator to evaluate the performance of ICF laser devices. By measuring the distribution of the X-ray generated from interaction between the third-harmonic beam and the target, the position information of the third-harmonic beam to the target can be obtained, along with the shooting accuracy. In the beam transmission process, the fundamental, second-harmonic beams and the third-harmonic beams approach to the target at the same time generating spurious X-ray. Based on the radiation fluid, the present paper is to assess the effect of the stray light on the performance of the shooting accuracy. The intensity distribution and power density of the fundamental, second-harmonic and third-harmonic beams at the target position were calculated for the SG-III laser device using SG-99 software. The characteristics of X-ray generated by the different beams radiation are simulated by one-dimensional radiation fluid program MULTI 1D. The results show that the power density of the fundamental, the second-harmonic and third-harmonic beams at the target position are, under the condition of typical shooting precision test (infused fundamental energy of 50J and pulse width is 200ps) 0.28GW / s / cm2 , 0.14GW / s / cm2 , 99GW / s / cm2 , respectively. The X-ray energy intensity radiated from the interaction between the third-harmonic beam and target is 104 times of that from the fundamental, second-harmonic beam. In the current optical system configuration conditions of SG-III laser device, the effects of the fundamental and second-harmonic beams on the target accuracy test can be ignored.
KEYWORDS: Clocks, Pulsed laser operation, Beam controllers, Signal generators, Laser optics, Picosecond phenomena, Seaborgium, Multiplexers, Temperature metrology, Control systems
The timing sequence, between different pulses in SG-III laser facility, is controlled with three arbitrary waveform generators. The external clock and trigger are used to inhibit the timing jitter, which is provided by the synchronization system. Close-loop monitoring is used to make sure that the temporal phase can be recovered after reboot of the arbitrary waveform generator. The verification experiment shows that the three arbitrary waveform generators can work synchronously , which ensures the synchronization error control of the SG-III laser facility.
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