Optomechanics with a polarization nondegenerate cavity

Experiments in the field of optomechanics do not yet fully exploit the photon polarization degree of freedom. Here experimental results for an optomechanical interaction in a polarization nondegenerate system are presented and schemes are proposed for how to use this interaction to perform accurate side-band thermometry and to create interesting forms of photon-phonon entanglement. The experimental system utilizes the compressive force in the mirror attached to a mechanical resonator to create a micromirror with two radii of curvature which leads, when combined with a second mirror, to a significant polarization splitting of the cavity modes.

Figure 1

(a) Compressive stress in the DBR layers causes the mirror to buckle. Inset shows optical image of the trampoline resonator. (b) Optical profiling with a confocal microscope reveals a concave mirror surface. (c) Local radius of curvature as function of angle obtained for the off-center location indicated with the white dot in panel (b). (d) Demonstration of mode splitting for an off-axis-aligned cavity by monitoring the transmitted intensity when the laser frequency is varied.

Figure 2

Optomechanical interaction for a polarization nondegenerate cavity. Blue points are extracted from the Lorentzian fit to the mechanical resonance. Red is a simultaneous fit of the data with four free parameters: optical linewidth, optical splitting, and input laser power for both modes. Green shows the contribution of the individual modes. Panel (a) shows the mechanical frequency shift and panel (b) shows the effective mechanical damping.

Figure 3

Effective temperature as a function of laser detuning. The arrow indicates the point where the contribution from both modes precisely cancel each other, leading to an effective temperature equal to the bath temperature.

Figure 4

A polarization nondegenerate cavity with a splitting $\delta =2{\mathrm{\Omega }}_m$. $H$ and $V$ denote the different polarization and corresponding cavity mode.