Speaker:  Dr. Christophe Pin

Assistant Professor, Research Institute for Electronic Science, Hokkaido University, Japan

Title: Surfing an optical potential slope by using a phase transition and the spin of light

Abstract:
Phase transitions often cause dramatic change of material properties. The insulator-to-metal phase transition of vanadium dioxide (VO₂) drastically modifies its optical properties at temperatures above 341 K. This temperature-dependent permittivity switching was found to induce the reversal of the optical trapping force acting on VO₂ particles in the vicinity of a focused infra-red laser beam. The trapped VO₂ particles are thus locked on a contour line of the beam intensity profile. The orbital rotation direction of the particle can be controlled by using a circularly polarized laser beam. Like dielectric particles trapped by the evanescent field around a tapered optical fiber, the local electric field intensity gradient enables spin-to-orbital angular momentum coupling via the directional scattering of light. In this seminar, I will discuss the possible mechanisms at the origin of right- and left-handed optical torques acting on VO₂ particles trapped in orbit around a focused laser beam.

References:
[1]Yoshito Y. Tanaka, Pablo Albella, Mohsen Rahmani, Vincenzo Giannini, Stefan A. Maier, and Tsutomu Shimura, “Plasmonic linear nanomotor using lateral optical forces,” Science Advances 6, eabc3726 (2020), DOI: 10.1126/sciadv.abc372

[2]Yoshito Y. Tanaka and Tsutomu Shimura, “Tridirectional Polarization Routing of Light by a Single Triangular Plasmonic Nanoparticle,” Nano Letters 17, 5, 3165–3170 (2017), DOI:10.1021/acs.nanolett.7b00672

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