Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 21: Poster Monday: Plasmonics and Nanooptics

O 21.3: Poster

Montag, 1. April 2019, 17:45–20:00, Poster F

Optical ratchet based on plasmonic waveguide arrays — •Zlata Cherpakova and Stefan Linden — Physikalisches Institut, Universität Bonn, Nußallee 12, 53115 Bonn, Germany

A ratchet is a spatially periodic system in which the directional transport of particles is achieved without a bias force. Based on the quantum-optical analogy, we propose a new design of a plasmonic ratchet and demonstrate directional transport of surface plasmon polaritons (SPPs). Our design resembles the time-dependent version of the Rice-Miele model: the couplings (i.e. the distances) between the adjacent waveguides and effective refractive indices (i.e. heights) are changing periodically. The plasmonic structures are fabricated by making use of negative-tone gray-scale electron beam lithography. SPPs are excited by shining a highly focused laser beam on the grating, deposited on top of the central waveguide. The spatial evolution of surface plasmon polaritons (SPPs) in the arrays is monitored by the leakage radiation microscopy. One observes an efficient directional transport of SPPs in such an array in a single preferred direction. Additional refractive index variation distinguishes our system from a simple combination of directional couplers. We show that even a very small height variation makes the SPP transport independent on the period of modulation. The role of the phase offset Δφ between the refractive index modulation and coupling modulation is investigated, the maximum transport efficiency is reached for Δφ=π/2