A side-pumped actively Q-switched Nd:YAG laser with pulse energy of >170 mJ, pulse duration of 6~7 ns and M2≈2.5 has been miniaturized, light-weighted and dimensioned for high electrical to optical efficiency. The key performance parameters and space qualification of the laser will be presented. Its performance and space environment reliability is suitable for space-borne altimeter.
Compared with conventional optical satellites, ZY-3(03) has its outstanding advantage in the combination of camera stereo observation and laser altimeter to directly obtain elevation control points, which can provide high-precision data for real three-dimensional China construction, geographic national conditions monitoring, farmland protection, geological disaster prevention, etc. In order to meet the demand of laser altimeter that the divergence angle is less than 0.1mrad, a laser beam expanding system is developed. The optical system with Galileo structure is composed of a negative lens group and a positive lens. Through the adjustment of the lens spacing and centering adjustment, the installation and adjustment of the beam expanding system under normal pressure is completed, and the wave-front error, defocusing and magnification are tested. In order to meet the conditions of vacuum use, vacuum presets are performed by adjusting the spacing between the front and rear lens groups. The vacuum divergence test of the transmitting system is carried out together with the laser. The measured divergence angle of the transmitting system is 0.084mrad, which meet the system design requirements. Subsequently, a mechanical environment test and a thermal vacuum environment test are carried out. The divergence angles before and after the tests, during the high and low temperature conditions are stable and are all less than 0.1mrad.
In order to satisfy the application requirements of spaceborne three dimensional imaging lidar , a prototype of nonscanning multi-channel lidar based on receiver field of view segmentation was designed and developed. High repetition frequency micro-pulse lasers, optics fiber array and Geiger-mode APD, combination with time-correlated single photon counting technology, were adopted to achieve multi-channel detection. Ranging experiments were carried out outdoors. In low echo photon condition, target photon counting showed time correlated and noise photon counting were random. Detection probability and range precision versus threshold were described and range precision increased from 0.44 to 0.11 when threshold increased from 4 to 8.
Solid laser pumped by semiconductor laser has the large value in the area of space laser technology, because of the advantages of high efficiency, small volume and long life. As the indispensable component of laser, laser power is also very important. Combined with ZY3(02) laser altimeter project, a high voltage(0~300V), high current(0~80A), long pulse width(0~230us) and high precision temperature semiconductor laser power is developed. IGBT is applied in the driving circuit as the switch to provide a current pulse for LD. The heating or cooling capacity of TEC is controlled by PID compensation circuit quickly adjusts the duty cycle of the UC1637 PWM signal, to realize the high accuracy controlling of LD working temperature. The tests in the external ambient temperature of 5°C, 20°C, 30°C show that the LD current pulse is stable and the stability of LD working temperature up to ±0.1°C around the set point temperature, which ensure the highly stable operation of DPL.
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