Tunable optical whispering gallery mode in a magnetic microsphere suspended in a ferrofluid

Abstract

Recent developments in microfluidic technologies have led to a growing interest in whispering gallery mode (WGM) optical resonators. In this report, we showed that in the case of TE waves, it is possible to induce such a mode in magnetizable microspheres suspended in a ferrofluid by applying static magnetic fields. The refractive index of a ferrofluid is dependent on the applied magnetic field. Considering this and using a quantum mechanical analog, radial distribution of the pseudo-potential is calculated for different fields and two different visible wavelengths. It is shown that within a certain range of the applied field, potential well is generated and WGM can be generated. Characteristics of the generated potential well are discussed. The finding may be useful for sensing applications in biotechnology and chemical technology.