Whispering gallery mode enhanced optical force with resonant tunneling excitation in the Kretschmann geometry

TL;DR

This paper investigates how whispering gallery modes excited via resonant tunneling in the Kretschmann geometry can significantly enhance optical forces, enabling high size-selectivity through boundary element method simulations.

Contribution

It introduces a detailed analysis of optical forces involving whispering gallery modes excited by evanescent waves, highlighting the effects of resonant tunneling and optimal separation in the Kretschmann configuration.

Findings

High contrast between on- and off-resonance forces enables size-selectivity.

Optimum separation balances intensity and Q factor for maximum force.

Different force behaviors observed at varying separations.

Abstract

The boundary element method is applied to investigate the optical forces when whispering gallery modes (WGMs) are excited by a total internally reflected wave. Such evanescent wave is particularly effective in exciting the high-$Q$ WGM, while the low angular or high radial order modes are suppressed relatively. This results in a large contrast between the forces on and off resonance, and thus allows for high size-selectivity. We fully incorporate the prism-particle interaction and found that the optical force behaves differently at different separations. Optimal separation is found which corresponds to a compromise between intensity and $Q$ factor.