Generation of THz radiation

Our current THz optoelectronics research focusses on the development of room temperature, ultra-compact and potentially portable THz sources emitting a few tens of µW powers 0.3–1.5 THz and beyond for Safety and Security applications, Quality control, Biophotonics and Medical Imaging, with the particular application for the non-invasive diagnostics and investigation of superficial cancers (skin cancers, gastric cancers, cervical cancers, colon cancers, etc.). This work is based primarily on the optimisation of devices and structures based on novel InAs/GaAs quantum-dots, dilute GaBiAs and GaInBiAs materials, as well as traditional materials such as low-temperature GaAs and InGaAs. The work was supported by EPSRC, EU-FP7 TERA, NEXPRESSO, and KTP projects.

The THz radiation is obtained by difference-frequency mixing of CW dual-wavelength emission from volume-Bragg-reflector or double-grating external-cavity edge-emitting lasers with novel semiconductor structures. Photoconductive mixers based on traditional and new materials and photovoltaic travelling-wave mixers have also been assessed, targeting increased conversion efficiency.

Recently, we demonstrated novel photoconductive quantum-dot based antennae for both the pulsed and CW THz generation, which work under unprecedented laser pump intensities with no saturation in conversion efficiency and without risking thermal breakdown. The newly built THz pump-probe setup was used to measure ultrashort carrier lifetime in quantum-dot wafers.