Large signal analysis of distributed feedback laser with three types spatial chirped grating and high reflection: Anti reflection facets

Abstract

In this paper, based on the coupled mode and carrier rate equations, the effects of different types of spatial chirped grating on a laser with distributed feedback (DFB), λ/4 phase shift, uniform injection current on the laser and high reflection in the rear facet were simulated and investigated for the first time. By using dynamic analysis with improved finite difference time domain (FDTD) numerical method in a single mode DFB laser with two way linear spatial chirped grating, the extinction ratio (ER) and high bit rate as a direct modulator and also making a high output optical power, were computed and analyzed. By adjusting the parameters such as spatial chirped grating, uniform injection current and the other physical parameters, the optical output power and side mode suppression ratio were obtained more than 28 mW and 80 dB respectively. Also by optimizing the physical parameters in DFB laser which is worked as a direct modulator, the bit rate and extinction ratio respectively 15 Gb and 50 dB were obtained. The obtained results from this simulation showed that using the reflection in the rear facet with a two way linear spatial chirped in the waveguide of the DFB laser improved output responses such as output optical power, side mode suppression ratio, (ER) and high bit rate in the direct modulator situation.