Mechanically robust waveguide integration and beam shaping of terahertz quantum cascade lasers

Terahertz-frequency quantum cascade lasers (THz QCLs) have numerous potential applications as 1–5 THz radiation sources within space-science, biomedical and industrial sensing scenarios. However, key obstacles to their widescale adoption outside laboratory environments have included their poor far-field beam quality and the lack of mechanically robust schemes that allow integration of QCLs with THz waveguides, mixers and other system components. In this letter, we present a block integration scheme in which a continuous-wave ∼3.4 THz double-metal QCL is bonded into a precision-machined rectangular waveguide within a copper heat-sink block. This highly-reproducible approach provides a single-lobed far-field beam profile with a divergence < 20 degree, and with no significant degradation in threshold current or range of operating temperature.