Mode-splitting of size-mismatched coupling microspheres

The “mode-splitting” phenomenon based on whispering gallery mode (WGM) was observed in coupling resonators, which are composed of two size-mismatched microspheres. The wavelength separation and intensity of the two splitting peaks varied with changing sized discrepancy for coupling microspheres. As the size of the first microsphere was fixed and coupled with a tapered fiber, it’s shown that the wavelength separation of two splitting peaks increased firstly and then decreased with the increasing size of the size-varied microsphere coupled to the first. The maximal wavelength separation could be achieved for identical-sized microspheres, with a minimal difference for intensity also noted. This analysis could provide better application prospects in measurement for judging similar-sized microspheres and measuring the size of microspheres.