  Plasmonic photoconductive antennas have great promise for increasing
responsivity and detection sensitivity of conventional photoconductive
detectors in time-domain terahertz imaging and spectroscopy systems. However,
operation bandwidth of previously demonstrated plasmonic photoconductive
antennas has been limited by bandwidth constraints of their antennas and
photoconductor parasitics. Here, we present a powerful technique for realizing
broadband terahertz detectors through large-area plasmonic photoconductive
nano-antenna arrays. A key novelty that makes the presented terahertz detector
superior to the state-of-the art is a specific large-area device geometry that
offers a strong interaction between the incident terahertz beam and optical
pump at the nanoscale, while maintaining a broad operation bandwidth. The large
device active area allows robust operation against optical and terahertz beam
misalignments. We demonstrate broadband terahertz detection with
signal-to-noise ratio levels as high as 107 dB.
