A ‘spaceplate’ approximates the angular response
of free space with a much thinner non-local metamaterial. They
have the potential to significantly shrink the volume of optical
and quasi-optical systems, by allowing elements such as lenses to
be moved closer together. However, spaceplates exhibit a trade off between their operational ...
A ‘spaceplate’ approximates the angular response
of free space with a much thinner non-local metamaterial. They
have the potential to significantly shrink the volume of optical
and quasi-optical systems, by allowing elements such as lenses to
be moved closer together. However, spaceplates exhibit a trade off between their operational angular and spectral bandwidth.
In this work, we present a new space-compression concept: a
dual-band spaceplate – capable of operating in two distinct
frequency bands simultaneously. This allows the limited spectral
bandwidth to be targeted to application specific parts of the
spectrum. Our design is composed of a multi-layer stack of semi transparent mirrors separated by free-space voids. These layers
act as a system of coupled Fabry-Perot cavities – the guided-mode ´
resonances of which emulate the effect of free-space propagation.
The stack is engineered to exhibit two resonant sub-bands, with
the frequency separation a tunable parameter in the design.
We numerically and experimentally demonstrate a dual-band
spaceplate exhibiting space-compression at two distinct frequency
sub-bands centered about 21.4 and 23.7 GHz.
