The side-mode-suppression ratio of a tunable DBR laser

Abstract

The authors investigate, both experimentally and theoretically, how the side-mode-suppression ratio (SMSR) of a multisection multiple-quantum-well distributed-Bragg-reflector (MQW-DBR) laser varies with tuning current. It is found that as the tuning current is adjusted the wavelength and the SMSR vary, with the peak SMSR=43 dB. The output power also varies with tuning current, and one can find when the laser is near a mode hop by examination of the light versus tuning current curve. This implies that the tuning current can be adjusted so that the laser frequency is near the center of the Bragg band without measuring the SMSR. The measurement are in good agreement with theory.