Subwavelength detection of terahertz radiation using GaAs HEMTs

We have designed and fabricated THz detectors based on excitation and rectification of radiation induced overdamped THz plasmons in InGaAs/GaAs HEMT structures. These plasma wave detectors were used to image the beam profile of THz gas laser operating at 1.63 THz with FWHM of 140 ¿m. The images were recorded with deep sub-wavelength spatial resolution. This allowed to resolve a sub-wavelength shifts in the detected THz responses from adjacent transistors with equivalent separation distances of 12 ¿m and 30 ¿m. Our results motivate the utilization of plasma wave detectors for near-field terahertz imaging and suggest the possibility of designing focal plane arrays with subwavelength pixel pitch.