Published online by Cambridge University Press: 01 February 2011
We report a simple and practical method to design and fabricate antireflection (AR) coatings for the emission facet of GaAs-based laser chips suited to operating in the very far infrared (IR) or terahertz (THz) spectral region. Vacuum-deposited silica films about 8 Ým thick serve as a single layer, quarter-wave AR and with reflectivities measured below 0.5% over ~10 cm-1 range in the far IR. Quantum cascade lasers (QCL) thus coated function well at 8-10 K coupled to a tunable, external cavity optical system at ~158 cm-1 (∼4.75 THz).