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Abstract Integrated optomechanical systems are a leading platform for manipulating, sensing, and distributing quantum information, but are limited by residual optical heating. Here, we demonstrate a two-dimensional optomechanical crystal (OMC) geometry with increased thermal anchoring and a mechanical mode at 7.4 GHz, well aligned with the operation range of cryogenic microwave hardware and piezoelectric transducers. The eight times better thermalization than current one-dimensional OMCs, large optomechanical coupling rates,g₀/2π  ≈  880 kHz, and high optical quality factors,Q_opt = 2.4 × 10⁵, allow ground-state cooling (n_m = 0.32) of the acoustic mode from 3 K and entering the optomechanical strong-coupling regime. In pulsed sideband asymmetry measurements, we show ground-state operation (n_m < 0.45) at temperatures below 10 mK, with repetition rates up to 3 MHz, generating photon-phonon pairs at  ≈ 147 kHz. Our results extend optomechanical system capabilities and establish a robust foundation for future microwave-to-optical transducers with entanglement rates exceeding state-of-the-art superconducting qubit decoherence rates. 

Since the advent of the laser, acousto-optic modulators have been an important tool for controlling light. Recent advances in on-chip lithium niobate waveguide technology present new opportunities for these devices. We demonstrate a collinear acousto-optic modulator in a suspended film of lithium niobate employing a high-confinement, wavelength-scale waveguide. By strongly confining the optical and mechanical waves, this modulator improves a figure-of-merit that accounts for both acousto-optic and electro-mechanical efficiency by orders of magnitude. Our device demonstration marks a significant technological advance in acousto-optics that promises a novel class of compact and low-power frequency shifters, tunable filters, non-magnetic isolators, and beam deflectors. 

Abstract Tuning and reconfiguring of nanophotonic components are needed to realize systems incorporating many components. The electrostatic force can deform a structure and tune its optical response. Despite the success of electrostatic actuators, they suffer from trade-offs between tuning voltage, tuning range, and on-chip area. Piezoelectric actuation could resolve these challenges, but only pm-per-volt scale wavelength tunability has been achieved. Here we propose and demonstrate compact piezoelectric actuators, called nanobenders, that transduce tens of nanometers per volt. By leveraging the non-uniform electric field from submicron electrodes, we generate bending of a piezoelectric nanobeam. Combined with a sliced photonic crystal cavity to sense displacement, we show tuning of an optical resonance by ~ 5 nm V⁻¹ (0.6 THz V⁻¹) and between 1520 ~ 1560 nm (~ 400 linewidths) within 4 V. Finally, we consider tunable nanophotonic components enabled by the nanobenders.