Optomechanically Induced Transparency and Cooling in Thermally Stable Diamond Microcavities

Abstract

Diamond cavity optomechanical devices hold great promise for quantum technology based on coherent coupling between photons, phonons and spins. These devices benefit from the exceptional physical properties of diamond, including its low mechanical dissipation and optical absorption. However the nanoscale dimensions and mechanical isolation of these devices can make them susceptible to thermo-optic instability when operating at the high intracavity field strengths needed to realize coherent photon-phonon coupling. In this work, we overcome these effects through engineering of the device geometry, enabling operation with large photon numbers in a previously thermally unstable regime of red-detuning. We demonstrate optomechanically induced transparency with cooperativity > 1 and normal mode cooling from 300 K to 60 K, and predict that these device will enable coherent optomechanical manipulation of diamond spin systems.

Realizing Q> 300 000 in diamond microdisks for optomechanics via etch optimization

“…The ability to operate at large N while avoiding thermal instability is practically important in cavity optomechanics applications due to the linear dependance of the optomechanical cooperativity C = 4g 0 N/κΓ m on N , where g 0 is the single-photon coupling rate, κ = ω o /Q o , and Γ m = ω m /Q m 9 . This enabled the observation of optomechanically induced transparency and optomechanically mediated wavelength conversion with C > 1 in previously reported work 63,66 .…”

“…The modified process used in Ref. 63 for fabricating improved microdisk optomechanical cavities is shown in Fig. 1, where the optimized steps that are the focus of this article have been highlighted in green.…”

“…While EBL offers ultra-high resolution nanolithography, it is vital to make the initial hard mask etch as smooth as possible to reap these benefits. Major limiting factors for Q of previously studied diamond microdisk structures were sidewall roughness and a "ledge" on the top edge of the microdisk 62,63 . Both of these imperfections were caused by a non-ideal hard mask etch that impacted the quality of the subsequent vertical diamond etched surfaces.…”

“…10(b) demonstrated an order of magnitude decrease in the thermal time con- stant of the microdisk structures, measured by fitting the response of the optical transmission for an input optical step function. This alteration resulted in the ability to support roughly an order of magnitude larger intracavity photon number before the onset of thermal instability 63 . The ability to operate at large N while avoiding thermal instability is practically important in cavity optomechanics applications due to the linear dependance of the optomechanical cooperativity C = 4g 0 N/κΓ m on N , where g 0 is the single-photon coupling rate, κ = ω o /Q o , and Γ m = ω m /Q m 9 .…”

Optomechanically amplified wavelength conversion in diamond microcavities

“…These devices were fabricated using an optimized reactive ion undercutting process described in Ref. 52 that results in a smooth diamond microdisk supported by a thin diamond pillar, and have higher Q o than those previously used for single-mode diamond optomechanics studies 26 .…”