Top grating index-coupled distributed feedback quantum cascade lasers

Abstract

We report on the modeling and design of top grating distributed feedback (DFB) quantum cascade lasers (QCLs). A low loss, index-coupled, DFB design that is very robust against technological spreads is proposed. Strong DFB coupling conditions are obtained while maintaining a high laser output power. Following this design, DFB QCL lasers with InP cladding layers and InGaAs∕AlInAs active regions have been fabricated. Room temperature monomode QCLs with 30dB side mode suppression ratios are demonstrated over a 4–8μm wavelength range.