Classification of whispering gallery modes for cladded systems

A classification of whispering gallery modes has been proposed between three types : core modes, cladding modes and composed modes. While core modes or cladding modes are interesting to generate with a sensor purpose, composed modes propagate in both core and coating and therefore should be avoided. In this paper, a theoretical and numerical study of modes insensitive to environment has been made. Numerical criteria are proposed in this paper to predict mode nature by comparing resonances for a threemedium system to approximated two-medium systems resonances. These criteria allowing to predict the type of the mode have been formulated and tested to various configurations of radii, indexes and cladding thickness. Results show that criteria have a high effectiveness for a strong difference between core and cladding indexes. If the normalized index is superior to 0.018, criteria predict the mode type with an accuracy superior to 95%. It is also shown that prediction accuracy is the greatest if cladding thickness is larger than the considered wavelength range here