The Research Of The Semiconductor Laser Power On The Stability

As the semiconductor laser is high transferring efficiency, small size, light weight, the high reliability, direct modulation and so on, it is widely used in in the fields of scientific research, industry, military, medical service and many other areas. But as far application, one of the main problem is that its output power is not stable.Semiconductor laser diode is a kind of device with high power density and sky-high quantum efficiency. Even weak drive current and temperature change will lead to its large change of output light power and device parameters, which directly damage the safe use of laser diode. At the same time, semiconductor laser diode is very sensitive to the temperature. The fluctuation of surrounding temperature not only leads to the fluctuation of supply current, but also makes threshold current, quantum efficiency, output wavelength and output light intensity of the laser diode change greatly. In order to reduce the influence of the laser diode's heat effect, a thermal control device is designed to make laser diode work under a stable temperature.In recent years, many researchers have been studying it. With the development of computer technology, the digital control, which is based on microcomputer, can solve effectively the problems of semiconductor laser on accuracy, stability, reliability. Therefore digital and intelligent control system must be the direction of development for semiconductor laser. In this paper, it introduces a control system. It is based on microprocessor and consists of three parts:1. Controlled driver part of LD. Since the LD is driven by injecting current, so we can control the power by control current. By the way of closed-loop feedback optical power, the signal of optical power is input to the MCU. After the CPU, the feedback signal is used to change the current in order to stabilize the optical power. At the same time, it provide a wide range of protection measures for laser.2. Part of temperature control. In this part, semiconductor cooler (TEC) is the implementation of devices, the MCU is the core. Software and hardware are designed of a combination of various parts of the circuit. We use the digital PID to calculate the control measure, and adopt the PWM to drive the TEC.3. Display and control of the keys. The LCD is used to display the optical power, through button control the beginning of the closure of system.