Mode selectivity of multisegment composite-cavity semiconductor lasers

Abstract The single longitudinal mode (SLM) characteristics of narrow linewidth long-external-cavity semiconductor lasers has been improved significantly by using a multisegment composite-cavity configuration. In this paper, the mode selectivities of two-segment, three-segment and four-segment cavity semiconductor lasers have been analysed and compared. In experiments, a four-segment composite cavity laser exhibits SLM oscillation with side-mode suppression ratio of 30 dB even for total external cavity length of 75 cm. The oscillation linewidth is less than 200 kHz.