To solve the small-optical aperture and stroke problem of existing fast steering mirror (FSM), we focus on the design of FSM driven by piezoelectric ceramics in space laser communication and lidar systems. The structure design of the FSM and the theoretical analysis of the piezoelectric actuators are carried out. The special structure and installation process of the mirror assembly are designed to ensure the accuracy of the mirror surface. Theoretical calculation and simulation analysis are conducted to evaluate the mirror’s output angle. The dynamic model of the FSM is established to analyze the stiffness. The operating principle and characteristic analysis results of FSM are verified by experimental tests. The results show that the FSM can provide a mechanical excursion angle of ±2.35 mrad, the closed-loop linearity of X axis and Y axis are 0.71% and 0.67%, respectively, and the closed-loop bandwidth of the FSM is 28 Hz. The surface shape accuracy of the mirror after installation can reach 1 / 50λ.
With the wide application of spaceborne lidar, 2 μm laser with high repetition rate and high energy has become an important candidate for coherent detection lidar. Conductively cooling is recognized as the critical technology for high energy, 2 μm lasers. The structure and thermal design of a totally conductively cooled, diode side-pumped, 2 μm laser amplifier is introduced in the paper. The amplifier consists of a 20-mm-long Tm: Ho: YLF crystal pumped by 2-banks of 3-radially arranged diode lasers (LD). Through the research and analysis of the structure and thermal coupling of the amplifier head, the conductively cooling scheme satisfying the need of the application in the space environment is obtained. The peak power consumption of LD is 200 W and the average heat consumption is 23.76 W at 10 Hz. When the coolant temperature is 17°C, the stable temperature of the crystal center is about 30°C, which achieves the result of 2.6 times of laser energy amplification. The experimental data matches the result very well.
We demonstrated a stable fiber laser setup for real-time monitoring of Tm-doped gain fibers while being exposed to gamma-rays. The output power is about 10W, and the power stability of the system is ±0.25% based on the 12-hour continuous measurement. By using this laser setup and 60Co gamma-ray irradiation source, the dose rate effect and total dose effect on the typical Tm-doped fiber specimens under water-cooling condition were experimentally studied. According to the obtained experimental results on five kinds of Tm-doped gain fiber from different R and D institutions and batches at home and abroad, the output power declines monotonously with the total irradiation dose increasing. During a dose rate range of 0.05 to 0.5 rad(Si)/s, the dose rate effects of Tm-doped gain fiber samples basically disappear, which means the differences of power degradation under different dose rate are almost invisible.
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