Efficient microparticle trapping with plasmonic annular apertures arrays

In this work, we demonstrate trapping of microparticles using plasmonic tweezers based on arrays of annular apertures. The transmission spectra and the electric-field distribution are simulated to calibrate the arrays. Theoretically, we observe sharp peaks in the transmission spectra for dipole resonance modes and these are red-shifted as the size of the annular aperture is reduced. We also expect an absorption peak at approximately 1115 m for the localised plasmon resonance. Using a laser frequency between the two resonances, multiple plasmonic hot spots are created and used to trap and transport micron and submicron particles. Experimentally, we demonstrate trapping of individual 0.5 m and 1 m polystyrene particles and the feasibility of particle transportation over the surface of the annular apertures using less than 1.5 mW m−2 incident laser intensity at 980 nm.