Microsphere resonators: a route to enhanced functionality in planar lightwave circuits

Microspheres coupled to planar optical waveguides through evanescent field interaction offer compact high-Q resonators combined with a flexible choice of resonator material for lasing, sensing, filtering or all-optical switching devices. Coupling on a planar optical circuit results in robust construction, straightforward alignment of multiple and concatenated resonators, direct access to evanescent fields, high compatibility with optical fiber applications and low cost of fabrication