A ring optical resonator is formed on a substrate. An outer circumferential surface of the resonator substantially confines one or more circumferential resonant optical modes. The resonator is positioned above a void formed in the substrate and is supported above the void by a portion of a material layer on the substrate that extends radially inward above the void from an outer circumferential edge of the void to the outer circumferential surface of the resonator. An optical waveguide can be integrally formed on the substrate and traverses a portion of the material layer above the void. The optical waveguide and the ring optical resonator are arranged and positioned so as to establish evanescent optical coupling between them. Q-factors of 108 or more have been achieved with a silica resonator and silicon nitride waveguide integrally formed on a silicon substrate.