Fig. 1. (a) Schematic of the array of nanoholes in a metallic film. Inset shows the unit cell of the presented nanohole arrays and the geometrical parameter symbols. (b) Simulation results of the normalized zero-order transmission spectrum. (c) Field distribution of |E| in the nanohole at the air–gold interface when a 760 nm laser illuminates from the −z direction.

Fig. 2. (a) Field distributions of |E| in the x–z plane when y is 0 nm. (b) Normalized intensity distributions of |E|2 along the dark dashed line in (a).

Fig. 3. (a) Calculated total potential along the dark dashed line in Fig. 2(a). (b) Potential distributions for point P in the x–y plane. Ux and Utot−x represent the optical dipole potential and the total potential along the x direction, respectively. The incident optical power P0=1  mW.

Fig. 4. (a) Contour plot of a trapping total potential in the x–y plane at z=372  nm for a unit cell. (b) Periodic arrays.