Transverse optical trapping force of absorbing double-layer spherical particles in a Gaussian beam

Abstract

In this paper, the transverse optical trapping of absorbing double-layer spherical particle is studied based on geometrical optics model. A model for double-layer spherical particle with optical absorption is presented. The transverse optical trapping force of a double-layer dielectric spherical particle with linear absorption in the outer layer illuminated by a focused Gaussian beam of TEM00 mode is simulated numerically. Our results show that the characteristicsof optical trapping, including the stable trapped positions, the peak intensityand the stiffness of stable trapping, greatly depend on by the absorption coefficient of the double-layer spherical particle. Besides, the ratio of the inner radius to the outer radius of the particle also has modulating influence on the properties of transverse trapping. It is possible to trap transversely the double-layer spherical particle with absorption on the axis of the incident Gaussian beam and on a circle centered at the optical axis for different axial offsets of sphere center from the beam waist as well.