Progress toward an athermal HEL optical window

Progress in the development phases of a new optical material that exhibits very low thermal lensing and robustness against thermal shock will be reported. Material, thermal, and optical properties of the current material formulation, called OFG-04, have been determined on small- and mid-scale samples. Manufacture scale-up to full-scale has been completed and flight windows prepared. Follow-on efforts are now beginning for an optimized formulation that will exhibit even lower bulk absorptance and OPD change with temperature rise.