Cavity Optomechanical Bistability with an Ultrahigh Reflectivity Photonic Crystal Membrane

Abstract

Photonic crystal (PhC) membranes patterned with sub‐wavelength periods offer a unique combination of high reflectivity, low mass, and high mechanical quality factor. Using a PhC membrane as one mirror of a Fabry–Perot cavity, a finesse as high as is demonstrated, corresponding to a record high PhC reflectivity of and an optical quality factor of . The fundamental mechanical frequency is 426 kHz, more than twice the optical linewidth, placing it firmly in the resolved‐sideband regime required for ground‐state optical cooling. The mechanical quality factor in vacuum is , allowing values of the single‐photon cooperativity as high as . Optomechanical bistability is easily observed as hysteresis in the cavity transmission. As the input power is raised well beyond the bistability threshold, dynamical backaction induces strong mechanical oscillation above 1 MHz, even in the presence of air damping. This platform will facilitate advances in optomechanics, precision sensing, and applications of optomechanically‐induced bistability.

Quasibound states in the continuum in photonic crystal based optomechanical microcavities

“…The predicted optical quality factors would result in a cavity decay rate of κ ≈ 2π × 100 MHz for a microcavity of L ≈ 1.55 μm length. Typical mechanical frequencies of suspended PhC membranes lie in the kHz to MHz range with an effective mass of a few nanograms [24][25][26][27][28][29]. When using such PhC membranes as an end-mirror [28] in our proposed microcavity, an optomechanical frequency pulling factor of about 2π × 100 GHz/nm would be realized, leading to a single-photon coupling strength on the order of 2π × 500 kHz and a ratio of coupling strength to optical loss of g 0 /κ ∼ 5 × 10 −3 , which is comparable to realizations based on optomechanical crystals [60], microwave optomechanics [61], or magnetomechanics [62][63][64].…”

“…Typical mechanical frequencies of suspended PhC membranes lie in the kHz to MHz range with an effective mass of a few nanograms [24][25][26][27][28][29]. When using such PhC membranes as an end-mirror [28] in our proposed microcavity, an optomechanical frequency pulling factor of about 2π × 100 GHz/nm would be realized, leading to a single-photon coupling strength on the order of 2π × 500 kHz and a ratio of coupling strength to optical loss of g 0 /κ ∼ 5 × 10 −3 , which is comparable to realizations based on optomechanical crystals [60], microwave optomechanics [61], or magnetomechanics [62][63][64]. Our proposed quasi-BIC optomechanical microcavity would be placed in the nonsideband resolved regime, which is amenable for optomechanical feedback cooling [65,66] and sensing [67].…”

“…In this article, we focus on analyzing practical optomechanical setups that realize optical quasi-BICs with photonic crystal (PhC) based optomechanical microcavities. Suspended PhCs combine excellent mechanical and optical properties due to their small weight, low mechanical dissipation, and engineerable optical reflectivity [24][25][26][27][28][29]. As a consequence, PhC slabs have been considered in theoretical proposals for optomechanical systems [30,31] and have been used in various optomechanical experiments already [28,[32][33][34].…”

“…Suspended PhCs combine excellent mechanical and optical properties due to their small weight, low mechanical dissipation, and engineerable optical reflectivity [24][25][26][27][28][29]. As a consequence, PhC slabs have been considered in theoretical proposals for optomechanical systems [30,31] and have been used in various optomechanical experiments already [28,[32][33][34]. Recently, it was shown that a cavity optomechanical system formed between two suspended PhC slabs realizes a Fabry-Perot-type optical BIC [5,8], exhibiting a quality factor only limited by intrinsic loss in the material [17,[35][36][37].…”