Back-scattering of whispering-gallery-modes resonances of cylindrical microcavities: Refractometric applications

Whispering-gallery modes (WGM) resonances of microcapillaries are directly compatible with microfluidic systems and have demonstrated its suitability for refractometric applications. Microcapillaries with a submicrometric wall exhibit very large wavelength shifts as a function of the refractive index of the liquids that fill the inside of the capillary. The spatial separation between the surface where the total internal reflection takes place (the outer surface) and the sensing surface (the inner surface) where the wave interacts with the analyte is a unique property that can be exploited to deal with analytes with a refractive index higher than that of the capillary. This paper proposes to monitor WGM resonances of cylindrical microcavities, as it is the case of thin microcapillaries, by measuring the spectrum of the reflected light. This will contribute to improve the performance of refractometric applications of these optical microcavities.