Design And Implementation Of Short Pulsed Driving Circuits Of Semiconductor Laser

Semiconductor lasers are widely used in laser communication, laser storage and laser ranging for its small size, low weight, low price, simple structure and long lifetime. Now, most of the LDs are electrical injection lasers. When the input current injected into the PN junction is higher than the threshold, the LDs will work and produce lasers. The output power will be decided by the amplitude of input currents. And the characteristics of the lasers will be decided by the characteristics of the input currents, including the pulse widths、amplitudes and repetition frequencies of the input pulses.In application such as laser processing, the characteristics and precision will be influenced by the laser power, and the power of lasers is decided by the pulse width and repetition frequency of the optical pulses. In different applications, the needed power is also different. When high power is needed, the laser pulses should have wide pulse width and high repetition frequencies. But when low power is wanted, the laser pulses should have short pulse width and low repetition frequencies.After comparing the advantages and shortages of the common short pulse generating methods, a short pulse driving circuit using FPGA and SERDES is designed in this paper. The parallel data produced by FPGA are converted to serial data, which has short pulse-width and high repetition-frequency. The pulse-width and repetition-frequency are both adjustable, among which the pulse-width can be adjusted from400ps to lms, the adjust step is from385ps to500ps, and the repetition-frequency can be adjusted discretionarily. The short pulse generated by the driving circuits can be used as the seed lasers in laser processing.When the semiconductor lasers work, parts of the electric energy will be transferred to heat. This will leads to the rise of the semiconductor lasers’temperature, and then its operating states, including wavelength, power and current threshold will be affected. In this paper, a temperature control circuit is designed to control the temperature of the semiconductor lasers. The circuit can detect and adjust the working temperature of the semiconductor lasers. It has high precision and can guarantee that the temperature of the semiconductor laser is around25℃.