Characteristics of double heterostructure PbS(1-x)Se(x) diode lasers prepared by compositional interdiffusion

The performance and characteristics of graded band-gap double heterostructure PbS(1-x)Se(x) diode lasers fabricated by a two-stage compositional interdiffusion technique have been studied. CW operation in these lasers was achieved easily when they were operated while immersed in liquid helium, when a minimum threshold current density of 10 A/sq cm and a maximum CW output power of 100 microW were observed. Despite the very low threshold current density, the devices did not emit continuously when operated while mounted on the cold finger of a liquid helium cryostat. This was attributed to the active region being overheated as a consequence of the high dislocation density (greater than 10 to the 6th/sq cm) of the substrates used in the device fabrication. A thermal analysis of the diode lasers has yielded a figure of merit which should be low for stable CW operation to be achieved.