Hybrid integration methodology for quantum cascade lasers with germanium waveguides in mid-IR

Abstract

Mid-infrared quantum cascade lasers (QCLs) operating around 5.7 μm have been integrated with germanium waveguides on silicon substrates. QCL bars have been designed and fabricated at the University of Sheffield for the purpose of integration. This hybrid approach uses flip-chip technology that has been successfully transferred from a silicon-on-oxide (SOI) platform working at communication wavelengths, demonstrating the flexibility of this approach. Integration challenges are introduced, and solutions discussed, leading to the next iteration of design presented here.