Resonantly driving crown modes in an optomechanical resonator

In this work, we have used a tapered fiber based pump-probe scheme to resonantly drive crown-type mechanical modes in a silica microtoroid. Crown modes exist in frequency degenerate orthogonal pairs. However, we demonstrate that due to energy and momentum conservation one mode is preferentially driven using this technique. To date, this has not been observed experimentally as studies have focused mainly on radial breathing modes (RBM), which do not possess a two-fold degeneracy. This work represents an important step towards nonlinear cavity optomechanics.