Microfabricated High-Q Optical Resonators for Microphotonics

Submillimeter-sized, transparent, solid, truncated spheres and ellipsoids for use as optical resonators in integrated microphotonic devices would be made by microfabrication techniques like those used in the electronic industry to make integrated circuits, according to a proposal. Such resonators, heretofore denoted generally as "microspheres," have been described in several recent articles in NASA Tech Briefs. In a microsphere, resonance is achieved through glancing-incidence total internal reflection in one or more "whispering-gallery" modes, in which the light propagates in equatorial planes near the surface, with an integer number of wavelengths along a nominal closed circumferential trajectory. If the surface of the resonator is sufficiently smooth and a sufficiently close approximation of a sphere or ellipsoid, then in principle, the resonance quality factor (Q) is limited only by attenuation in the resonator material; for a microsphere made of fused silica, this translates to a potential to obtain Q "e1010.