Coupled Cavity Mid-IR Quantum Cascade Lasers Fabricated by Dry Etching

Abstract

In this work, two-section, coupled cavity, mid-IR quantum cascade lasers (QCLs) were characterized in terms of their tuning range and emission stability under operation towards potential application in detection systems. Devices were processed by inductively coupled plasma reactive ion etching (ICP-RIE) from InP-based heterostructure, designed for emission in the 9.x micrometer range. Single mode devices were demonstrated with a better than 20 dB side mode suppression ratio (SMRS). The fabrication method resulted in improved yield, as well as high repeatability of individual devices. Continuous, mode-hop-free tuning of emission wavelength was observed across ~4.5 cm−1 for the range of temperatures of the heat sink from 15 °C to 70 °C. Using the thermal perturbation in the lasing cavity, in conjunction with controlled hopping between coupled-cavity (CC) modes, we were able to accomplish tuning over the range of up to ~20 cm−1.