Domain-engineered pyroelectric radiometer

We built a large-area domain-engineered pyroelectric radiometer with high spatial and spectral response uniformity that is an excellent primary transfer standard for measurements in the near- and the mid-infrared wavelength regions. The domain engineering consisted of inverting the spontaneous polarization over a 10-mm-diameter area in the center of a uniformly poled, 15.5 mm x 15.5 mm square, 0.25-mm-thick LiNbO(3) plate. Gold black was used as the optical absorber on the detector surface, and an aperture was added to define the optically sensitive detector area. Our results indicate that we significantly reduced the acoustic sensitivity without loss of optical sensitivity. The detector noise equivalent power was not exceptionally low but was nearly constant for different acoustic backgrounds. In addition, the detector's spatial-response uniformity variation was less than 0.1% across the 7.5-mm-diameter aperture, and reflectance measurements indicated that the gold-black coating was spectrally uniform within 2%, from 800 to 1800 nm. Other detailed evaluations of the detector include detector responsivity as a function of temperature, electrical frequency response, angular response, and field of view.