Optical characterization refractive index

For the unequivocal characterization of a low-molecular-weight compound, it is sufficient to specify a few physical or chemical properties, for example, boiling point, melting point, angle of optical rotation, refractive index, elemental analysis, IR and NMR spectra. If two low-molecular-weight samples have the same characteristic properties, they may be considered as identical. 

The characterization of sol-gel thin-film waveguides, passive or active, requires the measurement of a number ofphysical and chemical parameters, ranging from the topographical ones (e.g. roughness, waviness, thickness) to structural (porosity, hardness, amorphous or crystalline structure, composition) and optical ones (refractive index, absorption and emission, optical losses and optical gain). Most of these parameters can be measured by optical methods, and the most widely used methods and experimental configurations have been briefly described in the present chapter. The same procedures are generally applicable... 

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... 

Reffactometry is as unspecific as is absorption spectrometry, but has its merits if applied under well-characterized conditions. In 1984, Haubenreisser et al.30 reported on (a) the relation between transmission and refractive index characteristics, (b) the sensitivity, and (c) the working range of a fiber optic refractometer of mixtures of fluids. The U-shaped fiber reffactometer was shown to be useful for various physical quantities that vary with refractive index. 

Guided mode calculations were also carried out to compare the sensor response of several waveguide systems. In these simulations a model molecular monolayer is represented by a 2-nm thick layer with a refractive index of n 1.5. The optical properties of this model layer are typical of a dense layer of organic molecules on a substrate1 41, and are a reasonable approximation for a streptavidin protein layer bound to a biotinylated surface, the experimental model system we use to characterize our sensors. The ambient upper cladding was assumed to be water with a refractive index of n 1.32. For all examples, the lower cladding was assumed to be Si02 with an index of n 1.44. In the simulations, the effective index of... 

Here n5 and nm are the refractive indices of the microsphere and ambient medium, respectively, and R is the microsphere radius. To determine An and t from this equation, it is sufficient to measure AA for two wavelength, ly1 and A. In Ref. 36, this was done for A[ = 760 nm and A[ = 1,310nm. As the result the authors optically characterized a hydrogel nanolayer with 110-nm thickness and an extremely small excess refractive index of 0.0012, which was formed in situ in an aqueous environment. 

A wide range of physical constants, for instance melting point, boiling point, specific gravity, viscosity, refractive index, solubility, polymorphic forms vis-a-vis particle size, in addition to characteristic absorption features and optical rotation play a vital role in characterization of pharmaceutical chemicals and drug substances. These physical constants will be discussed briefly with typical examples as under ... 

The waveguides were optically characterized at X = 632.8 nm. The effective mode indices were determined by the m-line technique, based on a standard two prism coupling set-up. The refractive index depth profiles of the fabricated waveguides were reconstructed by the means of the inverse WKB procedure . 

Randomly distributed dipolar molecules form an isotropic medium characterized by a single refractive index n. When these molecules are more or less aligned in an electric field the medium becomes anisotropic and its optical properties must be described by two refractive indices. The Kerr cell consists of a glass vessel fitted with two parallel optical windows and two metal electrodes (Figure 2.11). The cell contains a liquid or a gas (solids can also be used) when an electric field exists between the electrodes the phase difference between the electric vectors is proportional to the square of the field and to the value of the electrical Kerr constant of the dielectric... 

Wang, X., Masumoto, H., Someno, Y., Hirai, T., (1998), Optical characterization of Si02-Ti02 thin films with graded refractive index profiles , J Japan Inst. Met, 62(11), 1069-1074. 

Many of the different susceptibilities in Equations (2.165)-(2.167) correspond to important experiments in linear and nonlinear optics. x<(>> describes a possible zero-order (permanent) polarization of the medium j(1)(0 0) is the first-order static susceptibility which is related to the permittivity at zero frequency, e(0), while ft> o>) is the linear optical susceptibility related to the refractive index n" at frequency to. Turning to nonlinear effects, the Pockels susceptibility j(2)(- to, 0) and the Kerr susceptibility X(3 —to to, 0,0) describe the change of the refractive index induced by an externally applied static field. The susceptibility j(2)(—2to to, to) describes frequency doubling usually called second harmonic generation (SHG) and j(3)(-2 to, to, 0) describes the influence of an external field on the SHG process which is of great importance for the characterization of second-order NLO properties in solution in electric field second harmonic generation (EFISHG). 

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