On the Possibility of Measuring the Abraham Force using Whispering Gallery Modes

TL;DR

This paper explores the potential of using whispering gallery modes in microresonators to experimentally detect the Abraham force, estimating the magnitude of the torque and assessing its experimental feasibility.

Contribution

It proposes a novel method to measure the Abraham force using intensity-modulated whispering gallery modes in microresonators, extending previous low-frequency approaches to optical frequencies.

Findings

Estimated Abraham torques are very small but potentially measurable.

Strong electromagnetic field concentration near the resonator rim enhances the torque.

The approach is feasible with current or near-future experimental techniques.

Abstract

Critical experimental tests of the time-dependent Abraham force in phenomenological electrodynamics are scarce. In this paper we analyze the possibility of making use of intensity-modulated whispering gallery modes in a microresonator for this purpose. Systems of this kind appear attractive, as the strong concentration of electromagnetic fields near the rim of the resonator serves to enhance the Abraham torque exerted by the field. We analyze mainly spherical resonators, although as an introductory step we consider also the cylinder geometry. The order of magnitude of the Abraham torques are estimated by inserting reasonable values for the various input parameters. As expected, the predicted torques turn out to be very small, although probably not beyond any reach experimentally. Our main idea is essentially a generalization of the method used by G. B. Walker et al. [Can. J. Phys. 53, 2577] for low-frequency fields, to the optical case.