Optomechanics with one-dimensional gallium phosphide photonic crystal cavities

• DOI: 10.1364/optica.6.000577
• Publication Date: 2019-04-26T15:12:20Z
• Authors: Katharina Schneider; Yannick Baumgartner; Simon Hönl; Pol Welter; Herwig Hahn; Dalziel J. Wilson; Lukas Czornomaz; Paul Seidler
• Keywords: Optomechanics; Gallium phosphide

Gallium phosphide offers an attractive combination of a high refractive index ($n>3$ for vacuum wavelengths up to 4 μm) and wide electronic bandgap (2.26 eV), enabling optical cavities with small mode volumes low two-photon absorption at telecommunication wavelengths. Heating due strongly confined light fields is therefore greatly reduced. Here, we investigate the benefits these properties cavity optomechanics. Utilizing recently developed fabrication scheme based on direct wafer bonding, realize integrated one-dimensional photonic crystal made gallium quality factors as $1.1\times10^5$. We optimize their design couple eigenmode $\approx 200$ THz via radiation pressure co-localized mechanical frequency 3 GHz, yielding sideband-resolved devices. The optomechanical coupling rate ($g_0=2π\times 400$ kHz) permits amplification into so-called lasing regime input power 20$ μW. observation implies multiphoton cooperativity $C>1$, important threshold realization quantum state transfer protocols. Because reduced thermo-optic resonance shift, optomechanically induced transparency can be detected room temperature in addition normally observed absorption.