SBIR-STTR Award

The U.S. military systems employs many EO/IR sensors platforms to enhance targeting, situational awareness, intelligence and reconnaissance operations.EMI/RFI and electronic signature control technologies of EO/IR sensors is therefore critical for the operation of the sensors. In addition, for platforms that require stringent RCS signature control, EO/IR sensors require to be placed behind RCS-complaint optical windows. Such platforms include Navy stealth ships EO/IR windows, fixed and rotary wing aircrafts EO/IR apertures, missile dome, and directed energy weapon apertures. Additional requirements include multi waveband operation and high optical transparency from visible to the IR. Current microwave absorbers are either made of optically opaque materials or require a metallic ground plane and thus are not transparent in the optical regime.We will design, fabricate and test a novel optically transparent microwave absorber based on doped monolayer and/or multi-layer graphene. Our technical approach can be tailored to meet specific optical and microwave requirements by design and/or chemically controlling the conductivity by doping. Graphenes conductivity can be voltage-controlled given the possibility for dynamically tunable microwave absorbers. Graphene sheets can be fabricated over large areas making it possible to develop transparent microwave absorbers for large optically transparent window applications for many different military platforms.

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.