Single-mode characteristics of short coupled-cavity semiconductor lasers

The characteristics of single-longitudinal-mode selection in short coupled-cavity (SCC) semiconductor lasers with a plane reflector are analyzed theoretically. It is found that the power ratio of the main mode to other side modes can be increased significantly by reducing the reflectivity of a laser diode facet adjacent to the external mirror. Based on the theoretical results, a new type of SCC laser is developed; single-longitudinal-mode output with 35-40 dB side mode suppression ratio is obtained under CW and 150 MHz modulation conditions.