Abstract
Assisted with Monte Carlo simulation, linear optical properties of soft matters such as liquid crystals, ferrofluids and liquids suspended with silica microspheres were investigated by transmittance, Faraday rotation and attenuated total reflection by exciting surface plasmons resonance.The microscopic structure of a thin liquid crystal film embedded between two glass plates when applying with electric fields was studied by the grand-canonical-ensemble Monte Carlo simulation. The time duration to reach the equilibrium state is successfully verified from the direct experimental measurement of light transmissions. The Kretschmann–Raether and the Otto configurations are implemented to generate surface plasmons and to examine the change of the refractive index of liquid crystals (LCs) by an applied field. The change of the minimum ATR angles does not agree with the calculation based on field-induced refractive-index change suggesting that the orientation of LC molecules adjacent to an electrode surface is unaffected by the external field because of the strong-anchoring effect. The aggregation and rearrangement of nanoparticles embedded in a thin cell of ferrofluid at various applied magnetic fields was studied by Monte Carlo simulation. Our model successfully simulate the reported experimental results by which the column size decreases as the ramp speed increases, implying that the time to arrive the final assembling state diminishes for a given final magnetic field. Physical parameters such as dielectric constant and susceptibility of dilute Fe3O4 ferrofluids derived directly from ATR and ferromagnetic resonance, respectively, were exploited to delineate the corresponding Faraday rotation angles with respect to the applied magnetic fields. Theoretical estimation was compared with experimental measurements ensuring that the effective medium theory is admittedly correct. Finally, the linear refractive indices of hydrated and dehydrated silica micro-spheres were studied under Kretschmann configuration to excite surface plasmons (SP), while the nonlinear second-order susceptibility was measured in direct transmission. An inconspicuous change for the case of dehydrated silica spheres is expected to be due to the small electro-optic (Pockels) effect, which is measured to have a linear electro-optic coefficients of . The SHG emission comes from the third-order susceptibility, which is a coupling of two photons and the electrostatic field induced by the surface –OH charges as characterized by the Gouy-Chapman model. The vanishing of SH signal from the dehydrated silica results from the loss of -OH group on the particle surfaces. Optical properties of dried silica spheres do not recover to its original hydrated state when pure water is refilled.