Top grating index-coupled distributed feedback quantum cascade lasers

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 30 dB side mode suppression ratios are demonstrated over a 4-8 mu m wavelength range. (c) 2008 American Institute of Physics.