Thin-film resonant absorbers for the far-IR spectral range were fabricated, characterized, and modeled. The 3-μm-thick structure comprises a periodic surface array of metal squares, a dielectric spacer and a metallic ground plane. Up to 95% absorption for the fundamental band at ~53.5μm wavelength (5.6 THz) is achieved experimentally. Absorption bands are independent of the structure period and only weakly dependent on polarization and incident angle. The results are well explained in terms of standing-wave resonances within individual metal-dielectric-metal cavities. The structure has application as a wavelength selective coating for far-IR bolometers.

Infrared-absorbing gold black has been selectively patterned onto the active surfaces of a vanadium-oxide-based infrared bolometer array. Patterning by metal lift-off relies on protection of the fragile gold black with an evaporated oxide, which preserves much of gold black's high absorptance. This patterned gold black also survives the dry-etch removal of the sacrificial polyimide used to fabricate the air-bridge bolometers. For our fabricated devices, infrared responsivity is improved 22% in the long-wave IR and 70% in the mid-wave IR by the gold black coating, with no significant change in detector noise, using a 300°C blackbody and 80 Hz chopping rate. The increase in the time constant caused by the additional mass of gold black is ∼15%.

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We present a design for a low-noise bolometer linear array based on the temperature-dependent conductivity of a VO xAu film. Typical thin film bolometers must compromise between low resistivity to limit Johnson noise and high temperature coefficient of resistivity (TCR) to maximize responsivity. Our vanadium oxide is alloyed with a small concentration of gold by co-sputtering, which gives very low resistivity and very high TCR simultaneously. The film is fabricated on an air bridge device having high thermal conductivity and small thermal time constant optimized for 30 to 60 Hz frame rates. The linear array functions as a low-power profile sensor with a modulated bias. For 1 V bias, we predict responsivity exceeding 1200 V/W. Johnson noise dominates with predicted NEP values as low as 1.0 x 10 -11 W/Hz 1/2 . Preliminary device testing shows film resistivity below 2.5 Ω-cm with TCR exceeding -2.0%. Preliminary measurements of NEP and D* are reported.