Applications of whispering gallery modes resonances of silica rods and microcapillaries

Cylindrical microcavities, as solid rods and microcapillaries, have several specific features compared to microspheres, microrings and microtoroids that make them particularly well suited for some applications. Making the optical resonances tunable is essential for many applications, and the cylindrical topology enables the implementation of several tuning techniques. In addition to thermal and strain tuning, slightly tapered rods, Erbium doped microresonators and liquid filled microcapillaries can be used to implement different tuning techniques. Optical fine tuning of whispering gallery modes (WGM) resonances is demonstrated using Erbium doped microresonators and an auxiliary 980 nm pump diode. Using a slightly tapered silica rod, the reflection produced by high Q WGM resonances can be exploited to make a tunable single-frequency fiber laser. WGM resonances of thin microcapillaries provide a unique solution for refractive index sensor applications, enabling the use of liquids with refractive higher than that of silica and offering an optimum compatibility between optical microcavities and microfluidics.