Bispectral optical cavity based on twin metamirrors

Abstract

In this work, we introduce a new bispectral optical cavity concept for which we design twin pairs of highly reflective, ultra-low noise metamirrors. Metasurfaces, artificial structures composed of periodic or quasi-periodic arrays of nanostructures, offer unprecedented control over light properties, paving the way for new applications in areas from high-precision optical metrology to quantum science. Custom phase and an ultra-high reflection coefficient make these metasurfaces an ideal candidate to surpass traditional multilayer mirrors as metamirrors in precision interferometry, particularly by also minimizing thermal noise. The focusing metamirrors designed in this study expect to reflect 99.95 % and 99.96 % of the incoming light at both, 1064 nm and 1550 nm wavelength. Their planar counterparts even reach theoretical reflectivities of 99.9999 % (1064 nm) and 99.9995 % (1550 nm). These specialized metamirrors enable bispectral low-noise optical cavities, which would reduce the number of cavities in optical experiments or could be used as a versatile transfer cavity for frequency locking.