Polygon Coherent Modes in a Weakly Perturbed Whispering Gallery Microresonator for Efficient Second Harmonic, Optomechanical, and Frequency Comb Generations.

We observe high optical quality factor (Q) polygonal and star coherent optical modes in a lithium niobate microdisk. In contrast to the previous polygon modes achieved by deformed microcavities at lower mechanical and optical Q, we adopt weak perturbation from a tapered fiber for the polygon mode formation. The resulting high intracavity optical power of the polygon modes triggers second harmonic generation at high efficiency. With the combined advantages of a high mechanical Q cavity, we observe optomechanical oscillation in polygon modes for the first time. Finally, we observe frequency microcomb generation from the polygon modes with an ultrastable taper-on-disk coupling mechanism.

Real-time electrical tuning of an optical spring on a monolithically integrated ultrahigh Q lithium nibote microresonator.

Cavity optomechanics, the study of the interplay between light and mechanical properties of matter, has triggered a wide range of research from cavity quantum electrodynamics, label-free single molecule detection to the creation of phonon lasers. Using femtosecond laser direct writing followed by chemomechanical polishing, here we report an ultrahigh quality (Q∼107) factor lithium niobate whispering gallery microresonator monolithically integrated with inplane microelectrodes. Coherent regenerative optomechanical oscillation with an effective mechanical quality factor as high as 2.86×108 is observed in air. We demonstrate real-time electrical tuning of the optomechanical frequency with an electromechanical tuning efficiency around -134 kHz/100 V.