Longitudinal and lateral interparticle optical binding and extrinsic radiation force and torque on a pair of lossless dielectric cylinders of arbitrary sizes and the acoustical analogue

Abstract

The purpose of this work is to develop an exact formalism and analytical equations for the interparticle electromagnetic/optical (longitudinal and lateral) binding forces arising between two lossless dielectric cylinders with different permittivities in a TE-polarized plane wave-field with an arbitrary incidence angle (in the polar plane). Additionally, the extrinsic/external optical radiation force and torque acting on the aggregate (i.e. the cluster of particle pair) are determined, and their exact mathematical expressions are derived. Based on the modal series expansion method in cylindrical coordinates in conjunction with the translational addition theorem, numerical simulations and computations for the longitudinal and lateral components of the interparticle and extrinsic forces as well as the axial component of the extrinsic torque show that attraction/repulsion, rotation clockwise or counter-clockwise, or neutrality, arise depending on the interparticle distance, the incidence angle, particle sizes and their dielectric permittivities. This investigation offers a complete analytical formalism without any approximations related to particle sizes. The numerical results computed based on exact mathematical expressions for interparticle and extrinsic physical observables can be used in the design and optimization of optical tweezers and related applications in optically-bound matter, particle manipulation, cloaking, and optically-assembled metamaterials with adjustable periodicities to name some examples. Also, the relevant analogy with the acoustic counterpart is noted.