Dynamic optical properties of gold nanoparticles/cholesteric liquid crystal arrays
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Research Letter
Dynamic optical properties of gold nanoparticles/cholesteric liquid crystal arrays Luciano De Sio, Beam Engineering for Advanced Measurements Company, Orlando, Florida 32810, USA; Department of Medico-surgical Sciences and Biotechnologies, Sapienza University of Rome, Corso della Repubblica 79, 04100 Latina, Italy; CNR-Lab. Licryl, Institute NANOTEC, 87036 Arcavacata di Rende, Italy Ugo Cataldi, Département de Chimie Physique, Université de Genev̀ e, Quai Ernest-Ansermet 30, 1211 Genev̀ e, Switzerland Alexa Guglielmelli, CNR-Lab. Licryl, Institute NANOTEC, 87036 Arcavacata di Rende, Italy; Department of Physics, University of Calabria, 87036, Arcavacata di Rende, Cosenza, Italy Thomas Bürgi, Département de Chimie Physique, Université de Genev̀ e, Quai Ernest-Ansermet 30, 1211 Genev̀ e, Switzerland Nelson Tabiryan, Beam Engineering for Advanced Measurements Company, Orlando, Florida 32810, USA Timothy J. Bunning, Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433-7707, USA Address all correspondence to Luciano De Sio at [email protected] (Received 23 January 2018; accepted 16 April 2018)
Abstract A thermoresponsive large-area plasmonic architecture, made from randomly distributed gold nanoparticles (GNPs) located at the substrate interface of a cholesteric liquid crystal (CLC) cell, is fabricated and thoroughly characterized. A photo-thermal heating effect due to the localized plasmonic resonance (LPR) mechanism is generated by pumping the GNP array with a resonant light beam. The photo-induced heat, propagating through the CLC layer, induces a gradual phase transition from the cholesteric to isotropic phase. Both the plasmonic and photonic properties of the system as both the selective reflection properties and frequency of the LPR are modulated.
Introduction In the last 20 years, plasmonic devices have been extensively investigated both from an experimental and theoretical point of view due to their fascinating and unique optical properties.[1–3] Several plasmonic-controlled photonic components have been realized including super-high-resolution lenses,[4,5] subwavelength gratings,[6] and beam deflectors.[7] Plasmonic nanoparticles (NPs) have played a key role in this explosion of interest due to their capability of confining electromagnetic radiation at the nanoscale by exploiting a phenomenon called localized plasmonic resonance (LPR).[8] Irradiation (with suitable frequency) of a plasmonic NP induces the oscillation of free electrons localized at the metal–dielectric interface, which gives rise to a LPR. The frequency (wavelength) of the LPR can be controlled by varying both the size, shape, and the dielectric constant of the surrounding medium.[9] Plasmonic NPs can also behave as nano-sized sources of heat when pumped sufficiently with resonant radiation due to the Joule effect generated by the photo-induced electrical current.[10,11] The photo-thermal properties of NPs have been historically considered a drawback because the
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