Develop Coatings that Repel Contamination

"Attenuated total internal reflection couples light from the inside of a transparent optical material into an absorbing contaminant contacting the polished surface of that material. If that contaminant is strongly absorbing and the angle of incidence isoptimized, more than 80% of the light is absorbed by the contaminant. At a certain mid infrared wavelength, water has very strong absorption, resulting in an absorption depth of less than one micrometer. We propose using pulsed mid infrared laser lightabsorbed by attenuated total internal reflection to remove water, ice, particles and other contaminants from the polished surfaces of optical elements, such as laser mirrors, windows and domes. Parasitic oscillations (total internal reflections) willlosslessly trap the light within the material until it illuminates a contaminated area, at which time attenuated total internal reflection will transfer some of the light into the contaminant, thus heating and removing that contaminant. Internallyreflected laser light may also be used to detect the presence of surface contaminants. For substrates not transparent at the mid infrared wavelength and in some other cases, the addition of a simple cover plate or coating may optimize the attenuation ofthe internal reflection and the contaminant removal process. Clean and dry polished surfaces are crucial for the successful operation of high power lasers, low scatter photographic/optical/lithogr