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Focusing membrane metamirrors for integrated cavity optomechanics
Version 2 2024-02-23, 17:00
Version 1 2024-02-01, 17:00
preprint
posted on 2024-02-23, 17:00 authored by A. R. Agrawal, J. Manley, D. Allepuz-Requena, D. J. WilsonWe have realized a suspended, high-reflectivity focusing metamirror ($f\approx 10$ cm, $\mathcal{R} \approx 99\%$) by non-periodic photonic crystal patterning of a Si$_3$N$_4$ membrane. The design enables construction of a stable, short ($L$ = 30 $\mu$m), high-finesse ($\mathcal{F}>600$) membrane cavity optomechanical system using a single plano dielectric end-mirror. We present the metamirror design, fabrication process, and characterization of its reflectivity using both free space and cavity-based transmission measurements. The mirror's effective radius of curvature is inferred from the transverse mode spectrum of the cavity. In combination with phononic engineering and metallization, focusing membrane mirrors offer a route towards high-cooperativity, vertically-integrated cavity optomechanical systems with applications ranging from precision force sensing to hybrid quantum transduction.