Design and fabrication of optical thin films for remote sensing instruments

Optical thin films designed for multispectral band-pass filters and a primary Ag mirror were deposited on radiation-resistant glass by ion-beam-assisted deposition. The filters and mirror are for use in the optical payload of a remote sensing instrument. The optical parameters of the films and mirror were optimized by using admittance loci analysis. The simulation shows that the band-pass filters can achieve average transmittances of 95% in the blue (B1), green (B2), red (B3), near-infrared (B4), and panchromatic (400-900 nm) spectral ranges and an average reflectance of 99% for the primary Ag mirror in the visible spectrum. The corresponding properties of the films were investigated by in situ optical monitoring, spectrometry, and high-resolution transmission electron microscopy. It was found that the average transmittances are above 85% for all five band-pass filters, with a rejection transmittance below 1% in the spectral range of 350-1100 nm. The average reflectance of the primary Ag mirror (with a protective coating) is above 98%. Interference coatings were added to the basic protected silver design to enhance the reflectance in the visible spectral range. Furthermore, to investigate the optical stability of optical thin films for aerospace applications, a space environment was simulated by using a Co(60) gamma (gamma) radiation source (total doses of 35 krad and 1 Mrad). The experimental results indicate that both the dielectric thin film stacks and radiation-protected glass are resistant to gamma radiation in the simulated space environment. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3453700]