Transient response analysis of semiconductor lasers at high frequency large signal pulse modulation

This paper presents analytical and numerical analysis of the pulse modulation response of semiconductor lasers. It pays a special attention to the transient response of semiconductor lasers under large signal modulation. The results from numerical solution of the rate equations reveal the difference between the more accurate nonlinear model and the small signal approximation. According to the study carried out in this paper, increasing the ratio of the amplitude of injection current to the threshold current can appreciably cut down the transient delays and so enhance considerably the speed of modulation. The idea has been examined on a typical commercial semiconductor laser. For example, the data from numerical solution shows 90 MHz signal modulation when the amplitude of signal is 3I_th, while increasing the amplitude to 6l_th, makes it possible for the laser to handle signal up to 260 MHz. Although the idea is examined in subGHz modulation, it may easily be extended to state of art semiconductor lasers at the range of several GHz.