Abstract
We present details of the fabrication and operating characteristics of quantum cascade distributed feedback lasers with lateral gratings. These devices emit light with a wavelength of similar to 10 mu m and operate with pulsed drive current above room temperature. InP-based material offers significant advantages over the GaAs system for mid-infrared quantum cascade lasers. High performance, single-mode lasers are achieved using InP-based material grown by metal organic vapor phase epitaxy and utilising double-sided lateral gratings. The deeply etched gratings were made possible by the development of a high aspect ratio, multi-stage, inductively coupled plasma (ICP) etch process, using Cl-2/Ar and SiCl4/Ar gas mixtures. Threshold current density was measured to be similar to 5.5 kA/cm(2) at a temperature of 293 K. Side mode suppression ratios > 20 dB and a tuning coefficient of -0.067 cm(-1) K-1 were observed.