Research On Two-dimensional Stability Control For CO₂ Laser With Line Selected By Grating

CO2 laser has been widely applied because of its advantage of high output power and energy conversion efficiency, long working hours, compact and light weight. The laser can be run by pulse or CW mode and be widely applied in laser radar, heterodyne detection, laser therapy, and other fields. In addition, CO2 laser is mainly used as the pumping source for optically pumped THz l aser system which can produce THz laser pulse. In order to obtain THz laser with high stability, the pump laser frequency should be stabilized at the resonance absorption frequency of the laser medium. The THz laser stability is directly influenced by CO2 laser frequency stability. In consequence, how to obtain CO2 laser beam with high stability has important application value and is also the purpose of this paper.When the laser is working freely, the stability of the laser is influenced by the change of the environment such as temperature, vibration, pressure. This paper want to study a two-dimensional real-time active compensation method to corrective laser perturbation. With using the installed two piezoelectric ceramic drive control grating frame, the laser output power stability can be improved by adjusting the grating spatial location.The main work of this paper includes following four parts. First, presenting the two-dimensional stability control technology for CO2 laser with line selected by grating based on the technology of stable cavity length control and stable grating line-tuning control. Second, choosing the method that applies the stochastic parallel gradient descent(SPGD) algorithm to realize two dimensional stable adaptive control. Third, completing the two-dimensional control system which including the exploitation of ADC module, DAC module, and the SPGD controller based on FPGA. Fourth, constructing the experimental system which realizes the closed-loop two-dimensional stability control for CO2 laser.The experiment results indicate that the method can realize laser power stable for a long time in maximum. Compared with no stability control, laser power longterm stability from 0.13 to 0.02, the average laser power increases by 10%. This method also can be used in other lasers for stability control.