A Parameter Optimization Based on Equivalent Circuit Model for High-speed DFB Laser

In order to improve the modulation rate and bandwidth of distributed feedback (DFB) laser, we propose a parameter optimization method based on the rate equation of semiconductor lasers. The derivation of the rate equation shows that the 3-dB bandwidth of DFB laser can be greatly improved by increasing the relaxation oscillation frequency. The relaxation frequency expression shows that the relaxation frequency is proportional to the differential gain coefficient and the steady state photon density, and inversely proportional to the photon lifetime and gain saturation factor. According to the principle of semiconductor laser performance analysis and parameter optimization, we theoretically deduce and simulate the parameters that affect the modulation characteristics of the laser. The range of the optimized parameters is determined. Within the determined range, the optimal parameters of the semiconductor laser are obtained by using the optimization software. An equivalent circuit model of DFB laser is established based on the rate equation, and the optimal parameters are substituted into the circuit model to verify the effectiveness of parameter optimization. This optimization method takes into account the feasibility of laser simulation and selects reasonable parameters in physical principles. The results show that the modulation rate of a DFB laser can be increased from 12GHz to 20GHz by using the parameter optimization method.