Design And Development Of Digital Controller For Intracavity Frequency-doubled DPSSL

Since the1990s, with the breakthrough of the high-efficient laser diode (LD) and the array of it, the LD pumped solid-state laser (DPSSL) broke the stagnation state and has entered a new era. DPSSL has wide applications because of its high efficiency, high frequency stability, narrow line width, high beam quality, long service life and the diffraction limit of laser beam. However, solid-state laser is very sensitive to temperature and drive current. Therefore, in order to obtain high-quality beam, the laser must have controller with high-performance. For simple applications, analog controller had already met the needs. But for higher requirement, digital controller must be needed.This thesis developed a high performance DPSSL laser controller with ADuC7028 as the core. Power feedback control is applied in the laser controller on the basis of the relationship of the laser drive current, operating temperature and output power. There are the negative temperature coefficient thermistor (NTC) and the semiconductor refrigeration chip (TEC) in the internal of the laser. The temperature control system is built based on the NTC and TEC, it employed a integral separated digital PID algorithm. The parameters were obtained through experiment testing method. The temperature control accuracy is within 0.02℃.To overcome the interference of uncertainty and make the laser output power stability, the laser are controlled in two ways: constant current mode and constant temperature mode, and both have satisfactory control effect. Under the conditions that the stability of the current reached 0.05% and the temperature control accuracy is within 0.02℃, the output light power stability of the LD pumped Nd:YVO4 solid laser with 50mW can be achieved 0.6% in the constant temperature control mode and 0.8% in the constant current control mode. The output light power stability of the laser under the control of the analog controller was 3%. It can be known from the comparison that the performance of the digital controller is better than the analog. In addition, the controller designed by this thesis realized the man-machine interaction through serial port, getting over of the difficulties in man-machine interaction of the analogue laser controller. Not only can it modify the laser operating parameters quickly and easily, but also monitor the operation status of the laser.