Microsphere Photolithography of Scalable Metasurfaces

Frequency Selective Surfaces/metasurfaces are arrays of subwavelength elements that provide a composite provide a composite electromagnetic response.  They allow wavelength dependent engineering of the scattering parameters with respect to amplitude, phase and polarization.  Metasurfaces have many potential applications including engineering radiation heat transfer, enhanced visible/IR spectrometery, structural color and metalenses.  The feature sizes of optical and infrared metasurfaces typically require fabrication using semiconductor techniques which is cost prohibitive for many applications. Our research uses Microsphere Photolithography to scale-up patterning metasurfaces.  This uses a self-assembled lattice of microspheres as an optical element.  Each microsphere focuses collimated radiation to a photonic nanojet inside a layer photoresist.  This technique results in hexagonal close packed lattices but can be used to define both unit-cell to unit-cell and sub-unit-cell hierarchical geometries by using appropriately structured illumination (e.g., using a digital micro-mirror array with tip/tilt stages).  The process can be adapted for patterning optical fiber as well as conformal surfaces.