Dynamic Control of Third-order Nonlinear Optical Properties of Gold Nanoparticle/Liquid Crystal Composites under External Electric Fields

TL;DR

This paper demonstrates how external electric fields can dynamically control the third-order nonlinear optical properties of gold nanoparticle/liquid crystal composites, enabling tunable photonic device applications.

Contribution

It introduces a method to manipulate AuNP alignment and plasmon coupling in liquid crystals using electric fields, which was not previously demonstrated.

Findings

Electric fields reorient liquid crystals and gold nanoparticles, affecting nonlinear optical responses.

Planar cells show controllable nonlinear absorption via LC reorientation.

Degenerate cells exhibit complex nonlinear behaviors due to multiple LC alignments.

Abstract

This study investigates the dynamic control of third-order nonlinear optical absorption properties of gold nanoparticles (AuNPs) dispersed in nematic liquid crystals (LC). By leveraging the reconfigurable nature of liquid crystals under external electric fields, we demonstrate the ability to manipulate AuNP alignment, dimer formation, and subsequently the plasmon coupling effects. Planar oriented and degenerate LC cells were prepared, and their optical responses under varying electric fields were characterized using polarization microscopy, UV-VIS spectroscopy, and Z-scan techniques. In planar cells, the applied electric field reorients LC molecules and AuNPs, influencing plasmon coupling and the nonlinear absorption. Conversely, degenerate cells exhibit more complex behaviors due to multiple LC alignment directions. These findings illustrate the potential of AuNP/nematic LC systems for creating tunable photonic devices responsive to external stimuli.