Numerical study of optical trapping properties of nanoparticle on metallic film with periodic structure

Based on the three-dimensional dispersive finite difference time domain method and Maxwell stress tensor equation, the optical trapping properties of nanoparticle placed on the gold film with periodic circular holes are investigated numerically. Surface plasmon polaritons are excited on the metal-dielectric interface, with particular emphasis on the crucial role in tailoring the optical force acting on a nearby nanoparticle. Utilizing a first order corrected electromagnetic field components for a fundamental Gaussian beam, the incident beam is added into the calculation model of the proposed method. To obtain the detailed trapping properties of nanoparticle, the selected calculations on the effects of beam waist radius, sizes of nanoparticle and circular holes, distance between incident Gaussian beam and gold film, material of nanoparticle and polarization angles of incident wave are analyzed in detail to demonstrate that the optical-trapping force can be explained as a virtual spring which has a restoring force to perform positive and negative forces as a nanoparticle moves closer to or away from the centers of circular holes. The results of optical trapping properties of nanoparticle in the vicinity of the gold film could provide guidelines for further research on the optical system design and manipulation of arbitrary composite nanoparticles.