Generating 10-GHz phonons in nanostructured silicon membrane optomechanical cavity

TL;DR

This paper demonstrates a silicon nanostructure that supports 10 GHz phonons with strong photon-phonon interaction, enabling room-temperature optomechanical resonators with high frequency and efficiency.

Contribution

It introduces a nanostructured silicon membrane design that achieves ultrahigh 10 GHz mechanical modes with strong photon-phonon overlap, surpassing previous frequency limitations.

Findings

Achieved 10 GHz mechanical frequency in silicon membrane

Demonstrated room-temperature operation with high photon-phonon coupling

Realized optomechanical micro-resonator with quality factor of 1000

Abstract

Flexible control of photons and phonons in silicon nanophotonic waveguides is a key feature for emerging applications in communications, sensing and quantum technologies. Strong phonon leakage towards the silica under-cladding hampers optomechanical interactions in silicon-on-insulator. This limitation has been circumvented by totally or partially removing the silica under-cladding to form pedestal or silicon membrane waveguides. Remarkable optomechanical interactions have been demonstrated in silicon using pedestal strips, membrane ribs, and photonic/phononic crystal membrane waveguides. Still, the mechanical frequencies are limited to the 1-5 GHz range. Here, we exploit the periodic nanostructuration in Si membrane gratings to shape GHz phononic modes and near-infrared photonic modes, achieving ultrahigh mechanical frequency (10 GHz) and strong photon-phonon overlap (61.5%) simultaneously. Based on this concept, we experimentally demonstrate a one-dimension optomechanical micro-resonator with a high mechanical frequency of 10 GHz and a quality factor of 1000. These results were obtained at room temperature and ambient conditions with an intracavity optical power below 1 mW, illustrating the efficient optical driving of the mechanical mode enabled by the proposed approach.