Thermo-optical properties and nonlinear optical response of smectic liquid crystals containing gold nanoparticles

Abstract

The present work is devoted to the study of the thermo-optical and nonlinear optical properties of smectic samples containing gold nanoparticles with different shapes. By using the time-resolved Z-scan technique, we determine the effects of nanoparticle addition on the critical behavior of the thermal diffusivity and thermo-optical coefficient at the vicinity of the smectic-A-nematic phase transition. Our results reveal that introduction of gold nanoparticles affects the temperature dependence of thermo-optical parameters, due to the local distortions in the orientational order and heat generation provided by guest particles during the laser exposure. Further, we show that a nonlinear optical response may take place at temperatures where the smectic order is well established. We provide a detailed discussion of the effects associated with the introduction gold nanoparticles on the mechanisms behind the thermal transport and optical nonlinearity in liquid-crystal samples.

Thermal optical non-linearity of nematic mesophase enhanced by gold nanoparticles – an experimental and numerical investigation

“…This nonlinear refractive index is related to the modulation of effective refractive index in the liquid crystal implicitly through eqns. (10)(11)(12)(13)(14)(15)(16). The temperature induced modulation of the effective refractive index [eqns.…”

“…The temperature induced modulation of the effective refractive index [eqns. (10)(11)(12)] causes a phase modulation [eqn. (13)] that diffracts a probe beam with strength measured by the diffraction efficiency parameter η [eqn.…”

“…(1) in combination with the absorbance coefficients listed in Table 5 and then using eqns. (10)(11)(12)(13)(14)(15)(16)18). The experimental data depicted in figure 8 are obtained from the measured diffraction efficiency in LCGNPs systems of varying GNP concentration and using eqn.…”

“…From the spatial temperature and orientation distribution, the corresponding refractive index grating is obtained using the Extended Cauchy model detailed in eqns. (10)(11)(12). The total phase shift of the incident probe beam of wavenumber k resulting from this refractive index grating is determined using the expression…”

Thermal Lens Study of NIR Femtosecond Laser-Induced Convection in Alcohols

“…It can be probed by monitoring the alteration of the wavefront of the light beam passing through it. Thermal lens effect was first observed by Gordon et al, who used a single laser beam for both pump and probe purposes. , Over the years, thermal lens spectroscopy has emerged as a highly sensitive tool to study photochemical reactions, − thermo-optical properties, − quantum yield, − low absorbance, trace analysis, nonlinear optical properties, and thermophoresis. − Since the first observation of the thermal lens effect, many different experimental configurations and theoretical models − have been developed to improve the sensitivity of TL apparatus and the analysis of the experimental signal. Unfortunately, these models are valid only for small phase change of the probe beam and only for the conductive mode of heat transfer.…”