Disordered zero-index metamaterials based on metal-induced crystallization

Zero-index (ZI) materials are synthetic optical materials with a vanishing effective permittivity and/or permeability at a given design frequency. Recently, it has been shown that the permeability of a zero-index host material can be deterministically tuned by adding photonic dopants. Here, we apply metal-induced crystallization (MIC) in quasi-random metal-semiconductor composites to fabricate large-area zero-index materials. Using Ag-Si as a model system, we demonstrate that the localized crystallization of the semiconductor at the metal/semiconductor interface can be used as a design parameter to control light interaction in such a disordered system. The induced crystallization generates new zero-index states corresponding to a hybridized plasmonic mode emerging from selective coupling of light to the Angstrom-sized crystalline shell of the semiconductor. Photonic doping can be used to enhance the transmission in these disordered metamaterials, as shown by simulations. Our results establish novel large-area zero-index materials for wafer-scale applications and beyond.