Conducting antireflection coatings with low polarization dependent loss for telecommunication applications.

Conducting optical coatings for the visible light range are commonly made of Indium Tin Oxide (ITO), but ITO is unsuitable for near-infrared telecommunications wavelengths because it can become absorptive after extended illumination. In this paper we show an alternative approach which uses conventional coating materials to create either non-conducting or conducting antireflection (AR) coatings that are effective over a fairly broad spectral region ( lambdalong/lambdashort approximately 1.40) and also usable for a wide range of angles of incidence (0-38 masculine, or 0-55 masculine) in the telecom wavelength range. Not only is the transmittance of windows treated with such coatings quite high, but they can be made to have extreme polarization independence (low polarization dependent loss values). A number of such coating designs are presented in the paper. A prototype of one of the conducting AR coating designs was fabricated and the measurements were found to be in reasonable agreement with the calculated performance. Such AR coatings should be of interest for telecommunication applications and especially for anti-static hermetic packaging of MEMS devices such as optical switches.