Plasmonics-enhanced large-area terahertz detectors (Conference Presentation)

Abstract

One of the main limitations for realizing high-performance time-domain terahertz imaging and spectroscopy systems is the low responsivity and narrow bandwidth of the existing pulsed terahertz detectors. In this work, we present a high-responsivity and broadband large-area terahertz detector that incorporates a two-dimensional array of plasmonic nanoantennas fabricated on a low-temperature-grown GaAs substrate. By using a large-area device architecture, large optical spot sizes can be used, mitigating the carrier screening effect at high optical pump powers. Using a large-area device architecture also makes the device less sensitive to changes in optical and terahertz alignment. The two-dimensional array of plasmonic nanoantennas is designed to offer a broad terahertz detection bandwidth. It is also designed to enhance optical absorption in close proximity to the nanoantennas by exciting surface plasmon waves. This allows drifting a large portion of photo-generated electrons and holes to the nanoantennas in presence of an incident terahertz pulse, offering high responsivity levels. We experimentally demonstrate detection of terahertz pulses with more than 5 THz bandwidth with high responsivity and signal-to-noise ratio levels exceeding that of electro-optic detectors. Such terahertz detectors would play a critical role in realization of the next generation time-domain terahertz imaging and spectroscopy systems.