Quantum well photoelastic comb for ultra-high frequency cavity optomechanics

Abstract

Optomechanical devices operated at their quantum limit open novel perspectives for the ultrasensitive determination of mass and displacement, and also in the broader field of quantum technologies. The access to higher frequencies implies operation at higher temperatures and stronger immunity to environmental noise. We propose and demonstrate here a new concept of quantum well photoelastic comb for the efficient electrostrictive coupling of light to optomechanical resonances at hundreds of GHz in semiconductor hybrid resonators. A purposely designed ultra-high resolution Raman spectroscopy set-up is exploited to evidence the transfer of spectral weight from the mode at 60 GHz to modes at 190-230 GHz, corresponding to the 8 th and 10 th overtone of the fundamental breathing mode of the light-sound cavities. The coupling to mechanical frequencies two orders of magnitude larger than alternative approaches is attained without reduction of the optomechanical constant g 0 . The wavelength dependence of the optomechanical coupling further proves the role of resonant photoelastic interaction, highlighting the potentiality to access strongcoupling regimes. The experimental results show that electrostrictive forces allow for the design of devices optimized to selectively couple to specific mechanical modes. Our proposal opens up exciting opportunities towards the implementation of novel approaches applicable in quantum and ultra-high frequency information technologies. a email:afains@cab.cnea.gov.ar 1 arXiv:1808.10029v2 [physics.optics] 19 Dec 2018Quantum coherent control of mechanical motion in atomic systems has been exploited since the early pioneering experiments with trapped ions. 1-5 Nano and micromechanical structures based on condensed matter devices extend these concepts with a great flexibility in design and the possibility to integrate different physical degrees of freedom. In addition, solid state devices allow the access to much higher mechanical frequencies, a critical requirement for quantum operation at higher temperatures and for the implementation of efficient ultrafast quantum information protocols. 6 The possibility to tailor the optical forces by sample design using material dependent electrostrictive forces was theoretically proposed in the context of waveguide optomechanics in Ref. 7. Here we propose and demonstrate through ultra-high resolution Raman spectroscopy, a quantum well photoelastic comb as a mean for the selective electrostrictive coupling of light to specific mechanical modes, and as a path to cavity optomechanics in the hundreds of GHz range, two orders of magnitude larger than alternative demonstrated technologies.Most cavity optomechanical devices operate with vibrational frequencies f m below or in the MHz range, with some designs pushing that limit to a few GHz. 6 Attaining higher mechanical frequencies without compromising other operational parameters is of critical relevance for various reasons. Firstly, to initialize a mechanical oscillator in the ground state at thermal equilibriu...

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