Thermodynamically limited uncooled infrared detector using an ultra-low mass perforated subwavelength absorber

Abstract

An uncooled detector has reached the thermodynamic temperature fluctuation limit, such that 98% of its total noise consisted of phonon and photon fluctuations of the detector body. The device has performed with a detectivity of 3.8×10 9 cmHz/W, which is the highest reported for any room temperature device operating in the long-wave infrared ( λ ∼8−12µm). The device has shown a noise-equivalent temperature difference of 4.5 mK and a time constant of 7.4 ms. The detector contains a subwavelength perforated absorber with an absorption-per-unit-thermal mass-per-area of 1.54×10 22 kg −1 m −2 , which is approximately 1.6–32.1 times greater than the state-of-the-art absorbers reported for any infrared application. The perforated absorber membrane is mostly open space, and the solid portion consists of Ti, SiN x , and Ni layers with an overall fill factor of ∼28%, where subwavelength interference, cavity coupling, and evanescent field absorption among units induce the high absorption-per-unit-thermal mass-per-area. Readout of the detector occurs via infrared-absorption-induced deformation using a Mach–Zehnder interferometry technique (at λ =633nm), chosen for its long-term compatibility with array reads using a single integrated transceiver.