Waveguide integration of a >4.7-THz quantum-cascade laser

We have demonstrated waveguide integration of terahertz quantum cascade lasers (THz QCLs) at frequencies above 4.7 THz. A precision micromachining technique, followed by diamond-turning and electroless-plating has been used to manufacture hollow rectangular waveguides with integrated diagonal feedhorns. We show that surface roughness at the 1μm level is achieved, enabling outcoupling of radiation in the 4.75–5.05 THz band, with a divergence angle of 5° along the plane of the QCL substrate.