Analysis of splitting direction for coupling WGM resonators

Abstract

The opposite splitting directions of mode splitting are observed in whispering gallery mode resonators, composed of coupling asymmetrical bispheres. A "virtual ellipsoid" model approximates the bispherical structure, linking the observed optical phenomena in bispheres to those in ellipsoids. The splitting characteristics are investigated theoretically and experimentally, including intensity difference and wavelength separation. The splitting direction is determined by the positions of the fundamental mode and azimuthal mode in the splitting peaks. Experimental results reveal that the resonant wavelength of the splitting peaks exhibits a redshift due to the increased diameter of Sphere D2, which is attributed to longer light propagation paths in the whispering gallery mode. The optical barcodes converted from transmission spectra provides potential applications for measuring the sizes of microspheres or ellipsoids, and their uniqueness can also be utilized for optical information identification.