Universal impedance matching and the perfect transmission of white light

Abstract

Light is reflected at the interface between heterogeneous media due to the mismatch of impedance(1-3). Removing this mismatch using additional materials, a technique known as anti-reflection, has so far been restricted to specific frequencies and incidence angles(3-7). The anti-reflection of white light, which requires the simultaneous matching of impedance over extremely wide angular and spectral ranges, has until now been considered impossible. Here, we develop a theory of universal impedance matching and introduce a matching layer that enables the perfect transmission of white light. The ability of a matching layer to assist in omnidirectional and frequency-independent anti-reflection has been confirmed analytically and numerically. We explain the feasibility of a universal matching layer using metamaterials, and demonstrate a transmission rate of over 99% for white light in the visible range with a double-layered dielectric metamaterial. This is confirmed experimentally by demonstrating the omnidirectional anti-reflection of microwaves in heterogeneous media.