Low Threshold Current Density (100) GaInAsP/InP Double-Heterostructure Lasers for Wavelength 1.3 µm

Abstract

Low threshold current density (100) GaInAsP/InP DH lasers emitting at 1.3 µm with thin active layer were studied experimentally and theoretically. The two phase solution growth technique was applied with low cooling rate of 0.08°C/min, which gave 0.05 µm thick uniform active layer. The threshold current density was minimized down to 770 A/cm2 with 0.13 µm thick active layer by reducing the concentration of Zn dopant, whereas the normal V–I characteristic was kept. The residual internal and the external absorption losses of the active layer were estimated to be about 70 cm-1 and 30 cm-1, respectively, in order to know the theoretical threshold limit. The narrowest beam divergence obtained was 23° for the active layer 0.05 µm thick. Both the threshold current density dependence on the thickness of the active layer and the beam divergence were in good agreement with the theory which was calculated by using the relative refractive index difference of 8.7%. A narrow stripe laser with undoped thin active layer had a tendency to emit in a single longitudinal mode.