Robust Nano-Structure Resonant Rejection Filters

High power laser rejection filters based on arrays of nanometer-scale structures fabricated in low absorption substrates have great potential for realizing robust protection windows for critical visible and infrared (IR) wavelength sensor systems. In this Phase I project, nano-structure resonant (NSR) narrow-band high reflector optics will be studied and prototyped. Designs incorporating a superposition of fine-scale randomly distributed features with larger scale periodic features will show high efficiency resonance for target rejection bands such as the 1030-1070nm band, combined with high transmission for out-of-band wavelengths in the visible and short-wave IR. Designs will be restricted to low refractive index, low absorption materials to realize the lowest electric field enhancement and highest damage resistance. GRISM based NSR designs typically exploited for spectral beam combining, will be explored as a robust single-material solution for high reliability. Coupon scale prototypes of the most promising NSR designs will be fabricated, characterized and delivered to the Army for CW laser damage testing. In a Phase I Option program, a second coupon scale prototype based on designs for operation in the MWIR to LWIR spectral region, will be fabricated, characterized and delivered. A Phase II project will scale-up of the proven designs from Phase I.