Mid-infrared quantum cascade laser integrated with λ/4-thick distributed Bragg reflector (DBR)

We report a first successful operation of a distributed Bragg reflector (DBR) integrated InP-based QCL. The DBR facet (λ/4-thick semiconductor-wall and λ/4-thick air-gap, 2 pairs) shows a high reflectivity of 91%, leading to a significant threshold current reduction of QCL in 7 µm wavelength region.