Experimental Demonstration of Optical Excitation of a Dual-Shell Resonator

This letter presents an optical method of excitation for a 3-D fused silica dual-shell resonator. Modulated light from a 980-nm laser diode was directed at the rim of the hemispherical resonator, exciting the n = 2 wineglass mode. The displacement amplitudes were measured as a function of laser power. For a nonmetalized, pristine, fused silica resonator, displacements up to 3 nm were measured at an average laser power of 140 mW. Modeling of the opto-thermal and radiation pressure effects revealed distinct underlying mechanisms: thermal effects were predicted to dominate the response of a metal-coated resonator, while radiation pressure was predicted to primarily contribute to the excitation of the uncoated resonator. In experiments, a metal-coated resonator exhibited the largest displacement, but its quality factor was degraded and frequency shifted by 4800 ppm. In contrast, the uncoated resonator achieved substantial displacements while preserving its high quality factor of 1.5 million, and its frequency shifted by only 33 ppm. This method of excitation demonstrates the feasibility of nonmetalized optical actuation and offers a pathway for ultra-high quality factor opto-mechanical resonators and gyroscopes utilizing only optical means for excitation and detection.