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

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Waveguide integration of terahertz quantum cascade lasers (THz QCLs) is demonstrated 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. It is shown that surface roughness at the level is achieved, enabling outcoupling of radiation in the 4.75–5.05 THz band, with a divergence angle of along the plane of the QCLs substrate.