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Free keywords:
MICROSPHERE RESONATORS; FREQUENCY COMBS; SENSORS; WATERPhysics;
Abstract:
We report on experiments on refractrometric sensing with crystalline Whispering Gallery Mode (WGM) resonators made of magnesium fluoride, which has a refractive index that is only slightly larger than that of water (Delta n approximate to 0.05). The resulting evanescent field of a WGM resonator placed in an aqueous environment penetrates therefore deep into the surrounding medium, which makes it a promising candidate for sensing applications. We measured a bulk index sensitivity of 1.09 nm/RIU (refractive index unit) in a resonator with a radius of R = 2.91mm and intrinsic Q-factors of more than 10(8) in aqueous environments. Furthermore, we describe the fabrication process of crystalline WGM resonators.
