Abstract
Optomechanical devices sensitively transduce and actuate motion of nanomechanical structures using light. Single--crystal diamond promises to improve the performance of optomechanical devices, while also providing opportunities to interface nanomechanics with diamond color center spins and related quantum technologies. Here we demonstrate dissipative waveguide--optomechanical coupling exceeding 35 GHz/nm to diamond nanobeams supporting both optical waveguide modes and mechanical resonances, and use this optomechanical coupling to measure nanobeam displacement with a sensitivity of $9.5$ fm/$\sqrt{\text{Hz}}$ and optical bandwidth $>150$nm. The nanobeams are fabricated from bulk optical grade single--crystal diamond using a scalable undercut etching process, and support mechanical resonances with quality factor $2.5 \times 10^5$ at room temperature, and $7.2 \times 10^5$ in cryogenic conditions (5K). Mechanical self--oscillations, resulting from interplay between photothermal and optomechanical effects, are observed with amplitude exceeding 200 nm for sub-$\mu$W absorbed optical power, demonstrating the potential for optomechanical excitation and manipulation of diamond nanomechanical structures.
Highlights
We have demonstrated an optomechanical system from single-crystal diamond and have shown that it possesses a unique combination of high sensitivity, broad bandwidth, high-quality single-crystal diamond material, high Qm, and low-power self-oscillation threshold
It has potential to enable measurement of quantum motion of nanobeam resonances and fundamental studies and technologies based on hybrid quantum devices
Excitation of nanomechanical self-oscillations with nW absorbed power illustrates the sensitivity of the diamond nanobeams to small driving forces, and their nonlinear dynamical softening provides a glimpse of the changing stress within the nanobeam during large-amplitude oscillations
Summary
Nanophotonic optomechanical devices [1,2,3,4] enable on-chip optical control of nanomechanical resonators with a precision reaching the standard quantum limit [5,6,7,8], enabling tests of quantum nanomechanics [7,9,10,11], as well as technologies for sensing [4,12,13,14] and information processing [15,16,17]. We report demonstration of single-crystal diamond optomechanical devices These devices allow low-power optical actuation of diamond nanomechanical resonators [29,30,31,32,33], and are predicted to enable optical control at wavelengths determined by the device geometry of spin transitions not accessible using traditional radio or microwave frequency techniques [19]. This sensitivity is less than a factor of 3 above the quantum uncertainty in position of the highest Qm nanobeams demonstrated in this work, and can be improved with further device optimization In combination, these properties make the demonstrated system promising for realizing optomechanical spin control, as well as fundamental studies of modification of nanomechanical resonator dynamics by coupling to electronic spins [39,40]. The analysis of the device properties and behavior presented here will guide future work to maximize strain coupling to electronic spins, and to harness the large photothermal force for optomechanical cooling and manipulation of nanobeam motion
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