Whispering-gallery modes in a microsphere coated with a high-refractive index layer:
polarization-dependent sensitivity enhancement of the resonance-shift sensor and TE–TM resonance matching
I. Teraoka, and S. Arnold
J. Opt. Soc. Am. B, 24, No. 3, 653 (2007)

Sensitivity enhancement of a whispering-gallery-mode microsphere resonance-shift sensor by coating of a
high-refractive index (RI) layer is examined for TM polarization. The enhancement of sensitivity in response to
particle adsorption or a RI change of the surroundings at the optimized layer thickness is greater for the TM
mode compared with the TE mode, but the TM mode requires a thicker layer. A particular choice of the layer
thickness allows the TE and TM shifts to match. Matching of the resonance frequency of the two modes is also
examined.