Abstract
We propose a versatile, free-space cavity optomechanics platform built from two photonic crystal membranes, one of which is freely suspended, and designed to form a microcavity less than one wavelength long. This cavity features a series of photonic bound states in the continuum that, in principle, trap light forever and can be favorably used together with evanescent coupling for realizing various types of optomechanical couplings, such as linear or quadratic coupling of either dispersive or dissipative type, by tuning the photonic crystal patterning and cavity length. Crucially, this platform allows for a quantum cooperativity exceeding unity in the ultrastrong single-photon coupling regime, surpassing the performance of conventional Fabry-Perot-based cavity optomechanical devices in the non-resolved sideband regime. This conceptually novel platform allows for exploring new regimes of the optomechanical interaction, in particular in the framework of pulsed and single-photon optomechanics.
Highlights
Cavity optomechanical devices [1] provide quantum control over their constituent mechanical and optical degrees of freedom for use in precision measurements, quantum networks, and fundamental tests
Free-space cavity optomechanics platform built from two photonic crystal membranes, one of which is freely suspended, and designed to form a microcavity less than one wavelength long
We propose a platform for cavity optomechanics, constructed from two suspended photonic crystal (PhC) slabs in an end-mirror configuration, that relies on photonic bound states in the continuum (BICs)
Summary
Cavity optomechanical devices [1] provide quantum control over their constituent mechanical and optical degrees of freedom for use in precision measurements, quantum networks, and fundamental tests. The advantage of out-of-plane geometries, such as Fabry-Pérot (FP) cavities in end-mirror [23,24,25], membranein-the-middle (MiM) [14], or levitated [5] configurations, is that a substantial proportion of light propagation is in vacuum This leads to lower optical decay rates (one can make the photon path length in the cavity longer) but this comes at the price of smaller single-photon coupling rates. We argue that near-wavelength and subwavelength localization of optical modes is a promising strategy for out-of-plane systems and that the DPhoC, with experimentally realistic parameters, can simultaneously possess the required optical and mechanical properties to access the strong quantum cooperativity regime on the single-photon level, without the encumbrance of an outer FP cavity
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