Unconventional Structure-assisted Optical Manipulation of High-index Nanowires in Liquid Crystals

David Engstrom, Michael C.M. Varney, Martin Persson, Rahul P. Trivedi, Kris A. Bertness, Mattias Goksor, and Ivan I. Smalyukh

Published by Optical Society of America Optics Express Vol. 20, Issue 7, pp. 7741-7748 (2012) https://doi.org/10.1364/OE.20.007741

Abstract

Stable optical trapping and manipulation of high-index particles in low-index host media is often impossible due to the dominance of scattering forces over gradient forces. Here we explore optical manipulation in liquid crystalline structured hosts and show that robust optical manipulation of high-index particles, such as GaN nanowires, is enabled by laser-induced distortions in long-range molecular alignment, via coupling of translational and rotational motions due to helicoidal molecular arrangement, or due to elastic repulsive interactions with confining substrates. Anisotropy of the viscoelastic liquid crystal medium and particle shape give rise to a number of robust unconventional trapping capabilities, which we use to characterize defect structures and study rheological properties of various thermotropic liquid crystals.

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