Graphene plasmons on attenuated total reflection structures: A route to achieve large optical pushing or pulling force intensities in the terahertz region

Abstract

The ability to control optomechanical interactions at subwavelength levels is of key relevance in modern optics. The present work focuses on the improvement of the force exerted on a dielectric nanoparticle placed near an attenuated total reflection structure containing graphene. Our results show that this force is highly dependent on the angle of incidence of the impinging plane wave, and it can be enhanced by nearly three orders of magnitude when this angle coincides with that of the critical total internal reflection and that corresponding to the excitation of surface plasmons along the graphene layer. New effects are found in these angular regions where the induced elliptical polarizability on the nanoparticle provides an asymmetric excitation of electromagnetic modes that generates a pulling (attractive) component whose magnitude is comparable to that of the pushing (repulsive) force provided by the incident field. As a consequence and contrary to what happens for large separation distances, an asymmetric response with respect to the angle of incidence arises for short distances for which the force on the particle is described by curves having a maximum and a minimum. Our results can contribute to a better understanding of polarization dependent interactions between nanoparticles and electromagnetic mode fields for taking advantage of them in nanoparticle manipulation applications.