Intensity dependent refractive index properties

This approach is based on the introduction of molecular effective polarizabilities, i.e. molecular properties which have been modified by the combination of the two different environment effects represented in terms of cavity and reaction fields. In terms of these properties the outcome of quantum mechanical calculations can be directly compared with the outcome of the experimental measurements of the various NLO processes. The explicit expressions reported here refer to the first-order refractometric measurements and to the third-order EFISH processes, but the PCM methodology maps all the other NLO processes such as the electro-optical Kerr effect (OKE), intensity-dependent refractive index (IDRI), and others. More recently, the approach has been extended to the case of linear birefringences such as the Cotton-Mouton [21] and the Kerr effects [22] (see also the contribution to this book specifically devoted to birefringences). 

The nonlinear optical properties of nematic liquid crystals have recently been studied by various authors. It has been shown that an intensity-dependent refractive index is due to the optical reorientation of the molecules. 

In Raman spectroscopy the intensity of scattered radiation depends not only on the polarizability and concentration of the analyte molecules, but also on the optical properties of the sample and the adjustment of the instrument. Absolute Raman intensities are not, therefore, inherently a very accurate measure of concentration. These intensities are, of course, useful for quantification under well-defined experimental conditions and for well characterized samples otherwise relative intensities should be used instead. Raman bands of the major component, the solvent, or another component of known concentration can be used as internal standards. For isotropic phases, intensity ratios of Raman bands of the analyte and the reference compound depend linearly on the concentration ratio over a wide concentration range and are, therefore, very well-suited for quantification. Changes of temperature and the refractive index of the sample can, however, influence Raman intensities, and the band positions can be shifted by different solvation at higher concentrations or... 

In diffuse reflection spectroscopy, the spectrometer beam is reflected from, scattered by, or transmitted through the sample, whereas the diffusely scattered light is reflected back and directed to the detector. The other part of the electromagnetic radiation is absorbed or scattered by the sample [124,125]. Changes in band shapes or intensity as well as signal shifts can be affected by morphological and physicochemical properties of the sample or combinations thereof (e.g., chemical absorptions, particle size, refractive index, surface area, crystallinity, porosity, pore size, hardness, and packing density [126]). Therefore, NIR diffuse reflection spectra can be interpreted in dependence of various physical parameters [127]. 

Properties such as volume, enthalpy, free energy and entropy, which depend on the quantity of substance, are called extensive properties. In contrast, properties such as temperature, density and refractive index, which are independent of the amount of material, are referred to as intensive properties. The quantity denoting the rate of increase in the magnirnde of an extensive property with increase in the number of moles of a substance added to the system at constant temperature... 

Figure 3 demonstrates the dependence of the intensity and the degree of hnear polarization of the reflected light on the particle properties and on the order of scattering. Since the effective refractive index of the medium is kept the same, the differences in the features of the opposition effects are caused by the differences in the microscopic characteristics of the scatterers. To explain the influence of the particle properties on the element, let us consider the interference of doubly... 

The problem of designing new polymer-based composite materials containing metal nanoparticles (MNPs) is of current interest, particularly in the fabrication of magnetooptic data storages, picosecond optical switches, directional connectors, and so on. The nonlinear optical properties of these composites stem from the dependence of their refractive index on incident light intensity. This effect is associated with MNPs, which exhibit a high nonlinear susceptibility of the third order when exposed to ultrashort (picosecond or femtosecond) laser pulses [1]. 

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