Eur. Phys. J. E (2012) 35: 33
https://doi.org/10.1140/epje/i2012-12033-x

Regular Article

Light-induced changes of the refractive indices in a colloid of gold nanoparticles in a nematic liquid crystal

¹ Institute of Physics, National Academy of Sciences of Ukraine, Pr. Nauki 46, 03028, Kyiv, Ukraine
² Department of Applied Physics, Aalto University School of Science, P.O.Box 13500, FI-00076 AALTO, Espoo, Finland
³ National Taras Shevchenko, University of Kyiv, Volodymyrs’ka str. 64, 01601, Kyiv, Ukraine
⁴ Department of Chemistry, University of Hull, Cottingham Road, HU6 7RX, Hull, UK

^* e-mail: ouskova@gmail.com

Received: 18 January 2012
Revised: 24 April 2012
Accepted: 24 April 2012
Published online: 17 May 2012

Abstract

It was shown that irradiation of a nematic liquid crystal doped with metal nanoparticles in the visible near the plasmon resonance band led to strong thermal changes of the refractive indices. The effect was studied by recording of dynamic optical gratings in the colloid. Nanoparticles “worked” as effective nano-heaters in a matrix causing the order parameter decrease around the particles. A large nonlinearity parameter (n ₂ ≈ 10^-2 cm²/kW and fast response (≈ 0.7 ms), with no detectable particles’ aggregation and excellent photo- thermo-stability make these colloids potentially attractive nonlinear optical media. Application of a dynamic holography technique allowed measuring the coefficients of thermal conductivity of the liquid crystal along the director k ^|| = (0.4 ± 0.02) W m⁻¹K⁻¹ and perpendicular to the director k ^⊥ = (0.2 ± 0.01) W m⁻¹K⁻¹.