Mie scattering and optical forces from evanescent fields: A complex-angle approach

TL;DR

This paper introduces a complex-angle approach to adapt Mie theory for analyzing scattering and radiation forces from evanescent fields, simplifying calculations and validating with existing methods.

Contribution

The authors develop a novel complex-angle method to extend Mie theory for evanescent wave scattering, providing a simpler and validated computational approach.

Findings

Accurate calculation of scattered fields in evanescent waves.

Validation against traditional methods shows perfect agreement.

Application to dielectric and conducting particles demonstrates versatility.

Abstract

Mie theory is one of the main tools describing scattering of propagating electromagnetic waves by spherical particles. Evanescent optical fields are also scattered by particles and exert radiation forces which can be used for optical near-field manipulations. We show that the Mie theory can be naturally adopted for the scattering of evanescent waves via rotation of its standard solutions by a complex angle. This offers a simple and powerful tool for calculations of the scattered fields and radiation forces. Comparison with other, more cumbersome, approaches shows perfect agreement, thereby validating our theory. As examples of its application, we calculate angular distributions of the scattered far-field irradiance and radiation forces acting on dielectric and conducting particles immersed in an evanescent field.