Optically pumped membrane BH-DFB lasers for low-threshold and single-mode operation

High optical confinement and high index coupling in 1.55 μm-wavelength GaInAsP-InP membrane buried heterostructure distributed feedback (BH-DFB) lasers consisting of deeply etched single-quantum-well wire-like active regions were demonstrated under room-temperature (RT) continuous-wave (CW) optical pumping. A threshold pump power of 1.5 mW and a submode suppression ratio (SMSR) of 42 dB were obtained for a 142-nm-thick membrane with a cavity length of 120 μm and a stripe width of 2 μm. We have also realized membrane BH-DFB laser arrays by arranging the laser cavities (10 μm spaced 15 elements with five different grating periods). A total wavelength span of 72 nm was achieved with a small lasing wavelength fluctuation up to 1.2 nm at RT-CW condition under optical pumping. From this value, membrane thickness fluctuation was estimated to be 0.4 nm. Threshold pump power of 3.4 mW and SMSR of 45 dB were achieved in a typical device.