GSMBE grown infrared quantum cascade laser structures

Abstract

In this paper we show the evaluated results of a quantum cascade laser (QCL) structure with a vertical transition and a Bragg reflector grown by gas source molecular beam epitaxy (GSMBE). The Al 0.48In 0.52As/Ga 0.47In 0.53As QCL structures lattice matched to the InP substrate consists of alternating 25 periods of undoped coupled-quantum-well active regions with compositionally graded layers, a superlattice graded region to provide strong electron confinement in the upper state using a Bragg reflector and an InP buffer layer. The laser operates in the temperature range from 8 to 250 K with measured integrated optical powers up to 70 mW at 8 K, and 5 mW at 250 K. The high-resolution emission spectrum of the laser at 250 K provides direct evidence of laser action from the narrowing of the strong line and clearly illustrating the longitudinal mode structure.