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

This work investigates the speed and responsivity of thermoelectrically coupled nanoantennas (TECNAs) in a vacuum. TECNAs are long-wave infrared (IR) detectors that absorb electromagnetic (EM) 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
$10.6 \, \mu \text{m}$
IR radiation. Improvements in responsivity ranging from
$3\times $
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.