Polarization-controlled particle transport with plasmonic teardrop-shaped nanostructure

In this article, we report a gold plasmonic teardrop-shaped nanostructure (PTNS) which can be used to transfer nanoparticles by switching the polarization of an excitation beam. The hot spots around PTNS provide efficient optical trapping sites whose locations are polarization-dependent. The teardrop tip generates an extremely strong local field enhancement, that enhances the trap stiffness and the possibility of transferring trapped particles between adjacent PTNSs. A nano-optical conveyor belt is constructed by a chain of uniform PTNSs that delivers target nanoparticles by periodically switching three polarization angles. Numerical analysis on optical forces and trap potentials confirms the feasibility of the design for particle trap and transfer. Furthermore, an 2D arrangement of PTNSs for particle gathering has also been demonstrated, benefiting from the polarization response of the tip. With the capability of large-scale capture and stable transfer, our design provides a general scheme for efficiently driving units in on-chip optofluidic applications.