Optical cages

Abstract

We examine arrays of metal-mesh frameworks for their wide-band absorption. These take the form of quasi-crystal optical cages. While there are many plasmonic structures that exhibit lossy behavior, they tend to be narrow band. By defining a quality loss metric, L = A/Q, where A is the absorption coefficient and Q is the quality factor, we are able to show that all absorbers fall in the range L:[0,2]. Metastructures have L∼0.04 while in our case L∼0.35. An array of cages tends to concentrate the incoming radiation within each framework. An array of cage-within-cage funnels the radiation from the outer cage to its inner core even further raising the possibility for new applications. We report on two surprising outcomes: copper based frameworks are better than silver based, and larger cage opening (thinner wires) are more effective than smaller openings (thicker wires).