Window Material for High Energy Laser Applications

High energy laser (HEL) window materials require high transmission of energy from directed energy (DE) devices while providing improved properties required for long life and affordable airborne application. The material must have low absorption and lowscattering in the laser wavelength region. Of the various candidate materials, ALON appears to be most promising because of its favorable properties such as excellent optical transparency, high hardness, high strength, durability, low intrinsic absorptioncharacteristic and large window size fabrication capability. Surmet Corporation proposes to develop high purity ALON as the window material for high-energy laser (HEL) directed-energy (DE) devices. Using an innovative cost-effective manufacturing processdeveloped by Surmet, Phase I research will attempt to determine the best ALON composition with high purity and very low optical absorption and scatter. Three compositions of ALON will be synthesized to form window size test coupons. These will becharacterized for purity, composition, absorption, scatter and temperature co-efficient of refractive index, in order to demonstrate the improved performance and suitability of this material for the intended HEL window application. At the conclusion of thePhase I research, the test size coupons of ALON will be delivered to the Air Force Program Manager for further evaluation for qualifying Surmet for a Phase II award. ALON is already being developed by Surmet for commercial uses as supermarket scannerwindows, scratch resistant lenses and windows, watch crystals, prisms, etc. The proposed research to improve the scatter and absorption properties of this important material via production of high purity ALON will make it suitable for high-energy laserwindow applications.