3.5-THz quantum-cascade laser emission from dual diagonal feedhorns

We present antenna-pattern measurements obtained from a double-metal supra-terahertz-frequency (supra-THz) quantum cascade laser (QCL) mounted within a mechanically micro-machined waveguide cavity and dual diagonal feedhorn assembly. With the QCL operating in continuous-wave mode at 3.5 THz, and at an ambient temperature of ~60 K, emission from both laser facets has been simultaneously directed to a suitable supra-THz detector mounted on a multi-axis linear scanner. Comparison of simulated and measured far-field antenna patterns shows an excellent degree of correlation between beamwidth (full-width-half-maximum) and sidelobe content. Furthermore, when compared with unmounted equivalents, very substantially enhanced QCL beam profiles are observed. Our novel device demonstrates the effectiveness of diagonal feedhorns intended for use in future spaceborne Earth-observing supra-THz heterodyne radiometers.