Tunable LWIR Notch Filter Metasurfaces

For dynamic protection of LWIR sensors from laser dazzler threats, Nanohmics, Inc., proposes to develop a thin, light-weight, electronically tunable notch filter based on microfabricated graphene-integrated metasurfaces. The optical filter can reject a specific narrow spectral line (“notch”) or multiple simultaneous notches. The metasurface comprises an engineered array of resonant microstructure nanoantennas that leverage standard materials and microfabrication techniques to reduce costs and provide a rapid route to commercialization. With no moving parts, the notch filter is rugged and consumes little power. In Phase I Nanohmics designed, fabricated, and tested proof-of-concept filters with TRL 3, demonstrating the feasibility of a tunable LWIR notch filter based on optical metasurfaces for dynamic protection of sensor instruments in the LWIR spectral band, 8-12 µm. Phase I laboratory tests and modeling strengthened the design for a scaled-up, high-rejection prototype, which will be developed to TRL 5 and provided to the Army by the end of Phase II. It will be thermally engineered to operate properly for optical irradiance of 100 mW/sq.cm. The thin (<5 mm) notch filter will be rapidly tunable with a switching rate of 60 Hz, and highly insensitive to polarization and angle of incidence, with an acceptance angle of ±32°.