Nanopowder-sintered materials challenge crystal-grown laser glass
YAG nanopowder materials with high purity can be used to manufacture laser weapon systems and transparent missile domes.
Air Force Research Laboratory (AFRL) contractor nGimat (Lexington, KY), taking advantage of the successful completion of Phase I and Phase II Small Business Innovation Research (SBIR) programs, has developed yttrium aluminum garnet (YAG) nanopowder materials with high purity from which laser weapon systems and transparent missile domes can be manufactured. These nanopowder materials improve over past suppliers so that polycrystalline ceramic methods can directly challenge the incumbent single-crystal growth process.
nGimat CEO Andrew Hunt says that YAG powders are available from a number of commercial sources. However, one such source sells 5 g of 99.5% purity powder for $250—too expensive and with inadequate purity. YAG powder is used most commonly as a phosphor to achieve a yellow color upon irradiation by blue light (for example, in lighting LEDs), but phosphors are too large in grain size to achieve the required purity levels that are possible with the nGimat NanoSpray combustion process. This process maintains the tight stoichiometry required to achieve phase purity for the nanopowder mixture. Hunt notes that the same material absorption in a smaller laser medium actually has higher total absorption in a larger, longer-path laser. In addition, as the laser gets larger, it is harder to get the resulting heat out of the laser because of its increased size. While a large, high-power, nanopowder-based laser has yet to be built for defense applications, experience with small- to medium-power lasers will enable scaling to high-power lasers as material purity levels improve with the NanoSpray process and dedicated processing equipment. Reference: http://science.dodlive.mil/2016/03/06/air-force-funds-efforts-to-mature-nanopowders-for-enabling-lasers.