Tailoring whispering gallery mode resonator for a wide range of potential applications: optoplazmonic erbium doped microspheres

Abstract Different WGM resonator geometries and materials can be used to tailor WGM resonators for specific applications. WGM resonators can reach ultra-high quality factors that lead to enhanced light-matter interaction. Additionally, the surface of a WGM resonator can be functionalized with a nanomaterial layer to enhance desirable optical properties, tailoring it further—from sensitivity to any perturbations of the surrounding environment to the generation of nonlinear effects at relatively low powers. Silica doped with erbium is widely used for optical amplification while metal nanoparticles act like nano-antennas and increase sensitivity to surrounding media. Doping silica microspheres with erbium ions, we have observed lasing at 1530 - 1560 nm at a threshold of 2 dBm (1.6 mW) when pumping with 1470 - 1500 nm. Lasing was also observed when additionally functionalizing the sphere surface with gold nanoparticles.