The Design And Achievement Of Temperature Controllerand Driver For Laser Diodes

Due to its miniaturization, high efficiency, simplicity, long life, etc., laser diodes (LD) has been widely used in many fields, such as data storage, measurement, atomic physics and pumping source for other laser system. However its output power and output wavelength rely on greatly the injection current and temperature stability.Since the LD came out, a lot of scientific research institutions and companies started to develop the temperature controllers and drivers. We first give briefly a review about this development both on the domestic and the international area and also give the prospects of the future research. We introduce in detail the design of a usual temperature controller and a driver, the demonstration of the linearity interpolation procession and the realization of the digital display and analyze the experimental results when applying on a LD.The thesis is divided into the following three parts:(1)The design of the temperature controller. Since the wavelength of the laser diode is sensitive to the temperature, the temperature must be controlled precisely in order to keep a constant wavelength. Based on the design scheme of C.C. Bradiey, considering the controlled system at our Institute, we accomplish a PID circuit of a temperature controller with adjustable PID parameters. This controller is used for an LD controlling. The experimental result indicates that the temperature stability around room temperature is better than 0.01 degree within 10 hours. (2)The design of the current driver. The output power of the laser diode is controlled by a current driver. LD is easy to be damaged by the surge voltage or surge current in the real situation if without protection. We thus design a current driver which can output constant current and has protection circuit. Also based on the work of C.C. Bradiey, constant current is realized with protection circuit, such as current limit which allows 6A of maximum current setting. 3 W and 5 W of the output power are obtained when used to drive the LDs and the power stability is better than 0.2% within 10 hours of continuous operation.(3)The displays of the temperature controller and current driver. The temperature controller and the driver can provide a voltage monitor of the actual temperature and current. In order to display such actual temperature and current, it is necessary to change the voltage into the corresponding temperature and current values. We successfully realize the temperature and current display based on microprocessor which can realize acquisition and display of multiple channels data in real time. The linearity interpolation process for thermistor improves the temperature accuracy.