Gold-black coatings for freestanding pyroelectric detectors

TLDR

The study details a gold‑black deposition process on freestanding pyroelectric detector substrates and compares it to prior literature. Gold‑black coatings were characterized using scanning electron microscopy, Fourier‑transform infrared reflectance, and spectral responsivity measurements. Spectrophotometry shows reflectance variations below 1 % below 2.5 µm and below 10 % at 10 µm, correlating with detector responsivity; spatial uniformity is better than 1 % at 1.25 µm and 5 % at 10.3 µm, and the coatings withstand a 193 nm laser damage threshold of ~38 mJ cm⁻².

Abstract

We describe the process of depositing gold-black on thin, freestanding pyroelectric detector substrates and compare this with previous work documented in the literature. We have evaluated gold-black coatings on thin, freestanding pyroelectric detector substrates by means of scanning electron microscope, Fourier transform infrared spectrophotometer reflectance, and spectral responsivity measurements. Spectrophotometric measurements indicate that reflectance at normal incidence varies by less than 1% at wavelengths shorter than 2.5 µm and by less than 10% at 10 µm. These results are correlated with the spectral responsivity of the detector and demonstrate that radiation not reflected by the gold-black is absorbed by the detector element. We have evaluated gold-black coatings as a function of position at two wavelengths and found variations of less than 1% at 1.25 µm and less than 5% at 10.3 µm, which demonstrates that spatial uniformity can be coating dependent. Gold-black coatings exposed to a 193 nm wavelength excimer laser were evaluated by visual inspection for damage and determined to have a damage threshold of approximately 38 mJ cm−2.