# 2015 CAP Congress / Congrès de l'ACP 2015

13-19 June 2015
University of Alberta
America/Edmonton timezone
Welcome to the 2015 CAP Congress! / Bienvenue au congrès de l'ACP 2015!

## High cooperativity optomechanics with wide-bandgap materials

18 Jun 2015, 10:15
15m
CCIS L2-200 (University of Alberta)

### CCIS L2-200

#### University of Alberta

Oral (Student, In Competition) / Orale (Étudiant(e), inscrit à la compétition) Division of Atomic, Molecular and Optical Physics, Canada / Division de la physique atomique, moléculaire et photonique, Canada (DAMOPC-DPAMPC)

### Speaker

Mr Matthew Mitchell (University of Calgary)

### Description

Cavity optomechanics provides a platform for exquisitely controlling coherent interactions between photons and mesoscopic mechanical excitations. Cavity optomechanics has recently been used to demonstrate phenomena such as laser cooling, optomechanically induced transparency, and coherent wavelength conversion. These experiments were enabled by photonic micro- and nanocavities engineered to minimize optical and mechanical dissipation rates, $\gamma_o$ and $\gamma_m$, respectively, while enhancing the per-photon optomechanical coupling rate, $g_0$. The degree of coherent photon-phonon coupling in these devices is often described by the cooperativity parameter, $C = N g_0^2 / \gamma_o\gamma_m$, which may exceed unity in several cavity optomechanics systems for a sufficiently large intracavity photon number, $N$. Here we demonstrate optical whispering gallery mode (WGM) microdisk cavities that are fabricated from wide-bandgap materials such as gallium phosphide (GaP), and single crystal diamond (SCD). By using wide-bandgap materials high-$C$ can be achieved by reaching high-$N$ before thermal instabilities occur. We demonstrate GaP microdisks with intrinsic optical quality factors $> 2.8 \times 10^5$ and mode volumes $< 10(\lambda/n)^3$, and study their optomechanical properties. We observe optomechanical coupling in GaP microdisks between optical modes at 1.5 $\mu$m wavelength and several mechanical resonances, and measure an optical spring effect consistent with a predicted optomechanical coupling rate $g_0/2\pi \sim 30$ kHz for the fundamental mechanical radial breathing mode at 488 MHz. We have also demonstrated monolithic microdisk cavities fabricated from bulk SCD via a scalable process. Optical quality factors of $1.15 \times 10^5$ at 1.5 $\mu$m are demonstrated, which are among the highest measured in SCD to date, and can be improved by optimizing our fabrication process further. In addition to SCD-possessing desirable optical properties, its high Young’s modulus, high thermal conductivity, and low intrinsic dissipation, show great promise for use in high-$C$ optomechanics. Current investigation is focused on characterizing the optical properties of these devices, and optimizing them for applications in nonlinear optics and quantum optomechanics.

### Primary author

Mr Matthew Mitchell (University of Calgary)

### Co-authors

Dr Aaron Hryciw (University of Alberta) Mr Behzad Khanaliloo (University of Calgary) Prof. Paul Barclay (University of Calgary)

### Presentation Materials

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