Gold-black coatings for freestanding pyroelectric detectors

Abstract

We describe the process of depositing gold-black on thin, freestandingpyroelectric detector substrates and compare this with previous workdocumented in the literature. We have evaluated gold-black coatings onthin, freestanding pyroelectric detector substrates by means of scanningelectron microscope, Fourier transform infrared spectrophotometerreflectance, and spectral responsivity measurements. Spectrophotometricmeasurements indicate that reflectance at normal incidence varies by lessthan 1% at wavelengths shorter than 2.5 µmand by less than 10% at 10 µm.These results are correlated with the spectral responsivity of the detector anddemonstrate that radiation not reflected by the gold-black is absorbed by the detectorelement. We have evaluated gold-black coatings as a function of position at twowavelengths and found variations of less than 1% at 1.25 µmand 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 wereevaluated by visual inspection for damage and determined to have adamage threshold of approximately 38 mJ cm−2.