Performance of Ultrafast, Nanoantenna-Based, Long-Wave Infrared Detectors in Vacuum

This work investigates the speed and responsivity of thermoelectrically coupled nanoantennas (TECNAs) in vacuum. TECNAs are long-wave infrared (IR) detectors that absorb electromagnetic radiation via a resonant dipole antenna. Joule heating within the antenna is converted to a voltage via a nanoscale thermocouple (NTC). Heat loss due to air is reduced under vacuum, allowing for improved device responsivity, but at the expense of speed. A finite difference model is introduced that calculates the steady-state and transient thermal transport within various TECNA designs across a range of ambient pressures. The modeled pressure dependence was derived from nanoscale convection coefficients found in the literature. Models were experimentally verified by studying the pressure-dependent and frequency-dependent voltage response of TECNAs exposed to modulated 10.6 μm IR radiation. Improvements in responsivity ranging from 3 to 4.5 times were demonstrated between atmosphere and vacuum, with 90% of improvement occurring between atmospheric pressure and 1 Torr (rough vacuum) in each design. Devices exhibited bandwidths of at least 10 kHz (roughly 100 times faster than common microbolometers) under vacuum with negligible signal attenuation, though future work is needed to fully characterize device frequency response.