Insight into optical gain effects in InGaAs/InP multiple-quantum-well laser diodes observed by uniaxial stress

Abstract

The inclusion of tensile strain in the active region of long wavelength laser diodes has been shown to improve the device efficiency and alter the polarization output. It has been proposed that this is due to the effect of strain on the valence band structure and a subsequent change in the polarization selection rules. We have used uniaxial stress to simulate tensile strain in the active region of bulk 1.55 micrometers InGaAsP laser diodes and lattice matched 1.55 micrometers InGaAs multiple quantum well laser diodes. We observed an increase in transverse electric (TE) threshold current in both types of device, but with different rates of change in the lasing wavelength with stress. To understand the observed increase in threshold current we modeled the bulk device using a 4 X 4 Luttinger-Kohn Hamiltonian and then used this to qualitatively explain the change found in the quantum well device. The loss mechanisms of Auger recombination and intervalence band absorption (IVBA) were found to play a significant role in the increase in (TE) threshold current with applied stress.