Improvement of trapping efficiency of Rayleigh particles using elliptical coaxial apertures

Plasmonic optical tweezers are the most promising candidates to overcome the diffraction limits imposed by conventional optical traps and high power levels to trap dielectric nanoparticles. In this paper we report the improved efficiency of the trap for sub-10 nm dielectric objects (Rayleigh particles) using elliptical coaxial apertures with and eccentricity of 0.85 when excited with linearly polarized light. The high intensification of the electric field at the ends of the semi-major axis of the elliptical structure allows a better localization of the hot spot that generates the unstable and almost isotropic optical force. Our simulations results show that the elliptical structure needs only 2mW of excitation power light to trap a Rayleigh particle in benzene solvent.