WGM microresonators: Light coupling issues and integration perspectives

In this paper, a brief analysis is presented of two critical issues for the full exploitation of the unique properties of microresonators based on Whispering Gallery Modes (WGM), namely the coupling of light into/out-of a WGM resonator (WGMR), and the integration of the WGMR with the light injection system and with other sub-systems (e.g. with microfluidics, in the case of biochemical sensors). The recent advances in WGMRs coupling to integrated optical waveguides and in the development of novel geometries, like microbubble resonators, seem to prove that effective integration is a feasible target and that these systems will soon be able to get out of the laboratories and to move to the market.