Optically Transparent Near-Perfect Microwave Absorber

Protecting electro-optical/infrared (EO/IR) sensors from electromagnetic interference (EMI) is critical for many military operations. Typically, these sensors are shielded using metal mesh and/or thin film coatings that reflect microwave frequencies but transmit the sensor operational bands. However, for platforms that require stringent radar cross-section (RCS) control, EO/IR sensors need to be placed behind RCS-compliant optical windows. This RCS requirement precludes the use of reflective EMI shielding. Additionally, current microwave absorbers are opaque to visible and IR wavelengths. To overcome these limitations, we design, fabricate, and test an optically transparent microwave absorber based on single/multi-layer graphene and silver nanowires. Our approach includes both Salisbury screen and metamaterial designs that can be tailored to meet specific optical and microwave requirements. We will explore several material combinations in the design with the goal of improved environmental and mechanical stability. Additionally, we will work toward material architectures that are amenable to high-rate manufacturing processes and can be easily retrofitted on current EO/IR sensor apertures.