Simulation for DFB Lasers with Grating Phase of pi on One Mirror Face

Abstract

In this paper, a simulation tool has been developed and the threshold gain and lasing frequency of a lasing mode in longitudinal direction of a 1.55um DFB(Distributed Feedback) laser with two mirrors and without anti-reflection coatings, that have both gain and index gratings, have been analyzed. The main purpose of this paper is to find an optimum value of grating phase of a mirror face and coupling strength in order to obtain excellent stable frequency operation of a single-mode during high-speed modulation. The grating phase of a left mirror face is fixed to be π and the grating phase of a right mirror face is varied. In order to obtain the largest gap in the oscillation threshold-gain between the first and second modes, DFB lasers should have coupling strength  =10 in case of Bragg deviation   . In case of   , the oscillation frequency selectivity of the single-mode is excellent in the range from  =2 to  =6, except of   phase= . If the goal is to minimize the oscillation gain, DFB lasers should have  =10, in order to enhance the backward scattering of the propagating light.