Thermal Radiation from Microsphere Photolithography Patterned Metasurfaces

Frequency-Selective Surfaces (FSS) type metasurfaces consist of periodic arrays of antenna elements. They can be scaled from microwave frequencies to the infrared wavelengths where they allow the scattering response to be engineered. This includes the spectral absorptance/emittance. At IR wavelengths, the features sizes of the metasurface are sub-micron which poses manufacturing issues for the meter squared scales required for most heat transfer applications. In this paper, we investigate the use of Microsphere Photolithography for creating spectrally selective metasurfaces. This approach uses a self-assembled array of microspheres as a lens array to focus a lattice of photonic jets into photoresist. These can be used with lift-off to create metal-insulator-metal (MIM) or even five-layer of resonant structures. We study the design constraints and synthesize a broadband emitter in the mid-infrared. The spectral absorptance is measured experimentally using FTIR. The structures are then tested at moderate temperatures to demonstrate the ability to affect surface temperature/heat flux in practical applications