Optical radiation force (per–length) on an electrically conducting elliptical cylinder having a smooth or ribbed surface

Abstract

The aim of this work is to develop a formal semi-analytical model using the modal expansion method in cylindrical coordinates to calculate the optical/electromagnetic (EM) radiation force-per-length experienced by an infinitely long electrically-conducting elliptical cylinder having a smooth or wavy/corrugated surface in EM plane progressive waves with different polarizations. In this analysis, one of the semi-axes of the elliptical cylinder coincides with the direction of the incident field. Initially, the modal matching method is used to determine the scattering coefficients by imposing appropriate boundary conditions and solving numerically a linear system of equations by matrix inversion. In this method, standard cylindrical (Bessel and Hankel) wave functions are used. Subsequently, simplified expressions leading to exact series expansions for the optical/EM radiation forces assuming either electric (TM) of magnetic (TE) plane wave incidences are provided without any approximations, in addition to integral equations demonstrating the direct relationship of the radiation force with the square of the scattered field magnitude. An important application of these integral equations concerns the accurate determination of the radiation force from the measurement of the scattered field by any 2D non-absorptive object of arbitrary shape in plane waves. Numerical computations for the non-dimensional radiation force function are performed for electrically conducting elliptic and circular cylinders having a smooth or ribbed/corrugated surface. Adequate convergence plots confirm the validity and correctness of the method to evaluate the radiation force with no limitation to a particular frequency range (i.e. Rayleigh, Mie or geometrical optics regimes). Particular emphases are given on the aspect ratio, the non-dimensional size of the cylinder, the corrugation characteristic of its surface, and the polarization of the incident field. The results are particularly relevant in optical tweezers and other related applications in fluid dynamics, where the shape and stability of a cylindrical drop stressed by a uniform external electric/magnetic field are altered. Furthermore, a direct analogy with the acoustical counterpart is noted and discussed.

Determination of scattering frequencies for two-dimensional acoustic problems using boundary element method

“…Particle pairs with corrugated surfaces are considered in electromagnetic problems 15 and a direct analogy with acoustic counterpart is discussed. 16 To simulate an unbounded domain with the finite element method, appropriate boundary conditions have to be imposed on the artificial boundary, which is considered as transparent boundaries. 13,[17][18][19] Otherwise, infinite elements 20 have to be employed.…”

“…Particle pairs with corrugated surfaces are considered in electromagnetic problems 15 and a direct analogy with acoustic counterpart is discussed. 16…”

Addendum: Radiation force and torque of light-sheets (2017 J. Opt. 19 065403)

“…Stemming from the law of momentum conservation and the light momentum integration using Poynting's vector formalism [7], the time-averaged optical radiation force vector and its Cartesian components have been determined [1,[8][9][10][11][12][13][14][15][16][17][18][19]. The optical radiation force analysis of the GLMT for a spherical particle [20] has been based upon integrating the Poynting vector over a surface in the far-field enclosing the particle.…”