Short cavity membrane BH-DFB laser with λ/4 phase shift

Membrane buried heterostructure distributed feedback (BH-DFB) lasers with cavity length as short as 50 μm consisting of deeply etched single-quantum-well (SQW) wire-like active regions and λ/4 phase shift were demonstrated under room-temperature continuous-wave (RT-CW) optical pumping. Threshold pump power of 3.1 mW and sub-mode suppression ratio (SMSR) of 35 dB were obtained with focused light spot of 120 μm (length) × 4 μm (width). The corresponding threshold for current injection was estimated to be roughly 70 μA. Lasing wavelength of 1549 nm corresponded to the Bragg wavelength and the equivalent refractive index was estimated to be 2.50. The stop-band width was observed to be 38 nm and the index-coupling coefficient of the grating structure was estimated to be 710 cm^-1.