We use Z-scan technique to investigate the nonlinear optical response of the thermotropic liquid crystal E7 in the neighborhood of the nematic-isotropic phase transition. The analysis of the data for the nonlinear optical birefringence is compatible with an effective critical exponent of the order parameter, β = 0.28 ± 0.03, which is close to the classical value, β = 0.25 , for a tricritical point. The nonlinear optical absorption in the nematic range depends on the geometrical configuration of the nematic director with respect to the polarization beam, and vanishes in the isotropic phase.

Ferrouids are colloids of superparamagnetic nanoparticles that are envisaged for use in hyperthermia, which is based on nonradiative relaxation after interaction with a high-frequency magnetic eld or light. For such applications, an important parameter is the thermal diusivity. In this communication, we present an experimental study of the dependence of thermal diusivity of ferrouids on the size of the magnetite nanoparticles by employing the mode-mismatched thermal lens technique. The results show a huge enhancement of the thermal diusivity by increasing the average size of the nanoparticles, while the number density of the nanoparticles is maintained as constant.

Plasmonic nanofluids have found applications in many fields, for example, coolants, solar collectors, and theranostics agents. For such applications, an important parameter is the thermal diffusivity. In this communication, we present an experimental study concerning the dependence of the thermal diffusivity of highly diluted aqueous plasmonic nanofluids containing PVP-coated silver nanoparticles on the concentration. Measurements were made by employing the time resolved mode-mismatched thermal lens technique and the results show an enhancement of the thermal diffusivity, when compared to that of the carrier fluid, on increasing the number density of the nanoparticles and being rather constant as a function of the power of the pump beam.

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