3.5 THz quantum-cascade laser emission from dual diagonal feedhorns

B N Ellison,A G Davies,A Valavanis,E Zafar,O Auriacombe,G Savini,M Emes,E Saenz,D Walker,E H Linfield,Y Han,M L Oldfield,N Brewster,L H Li,T Rawlings,B Winter,D Gerber

doi:10.1017/s175907871900028x

Abstract

AbstractAntenna-pattern measurements obtained from a double-metal supra-terahertz-frequency (supra-THz) quantum cascade laser (QCL) are presented. The QCL is mounted within a mechanically micro-machined waveguide cavity containing dual diagonal feedhorns. Operating in continuous-wave mode at 3.5 THz, and at an ambient temperature of ~60 K, QCL emission has been directed via the feedhorns to a 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 and a very substantial improvement when compared with unmounted devices. Additionally, a single output has been used to successfully illuminate and demonstrate an optical breadboard arrangement associated with a future supra-THz Earth observation space-borne payload. Our novel device has therefore provided a valuable demonstration of the effectiveness of supra-THz diagonal feedhorns and QCL devices for future space-borne ultra-high-frequency Earth-observing heterodyne radiometers.

Highlights

The Earth’s upper atmosphere plays an important role in influencing weather and future climate change
We present the development of a 3.5 THz quantum-cascade-laser (QCL) source and its integration within a precisionmachined waveguide cavity that includes two miniature diagonal feedhorns
Integration with a mechanically fabricated waveguide and feedhorn antenna structure offers the possibility of enhancing the quantum cascade laser (QCL) output signal by constraining it to a propagation mode that results in improved beam quality, and simultaneously allows coupling to a mixer diode mounted within the same waveguide

Summary

Introduction

The Earth’s upper atmosphere plays an important role in influencing weather and future climate change. This presents a very considerable technical challenge because it requires the development and integration of complex heterodyne radiometer technologies that include, for example, supra-THz frequency mixer and local oscillator (LO) components, spectral signal processing systems, and precision optical interfaces. In addition to measuring resultant beam quality of the QCL output at 3.5 THz, we have illuminated a breadboard antenna system concept that is compliant with passive sampling of the MLT

Results

Conclusion