Nonlinear optical properties light scattering

The nonlinear optical (NLO) susceptibilities of bioengineered aromatic polymers synthesized by enzyme-catalyzed reactions are given in Tables 2, 3, and 4. Homopolymers and copolymers are synthesized by enzyme-catalyzed reactions from aromatic monomers such as phenols and aromatic amines and their alkyl-substituted derivatives. The third-order nonlinear optical measurements are carried out in solutions at a concentration of 1 mg/mL of the solvent. Unless otherwise indicated, most of the polymers are solubilized in a solvent mixture of dimethyl formamide and methanol (DMF-MeOH) or dimethyl sulfoxide and methanol (DMSO-MeOH), both in a 4 1 ratio. These solvent mixtures are selected on the basis of their optical properties at 532 nm (where all the NLO measurements reported here are carried out), such as low noise and optical absorption, and solubility of the bioengineered polymers in the solvent system selected. To reduce light scattering, the polymer solutions are filtered to remove undissolved materials, the polymer concentrations are corrected for the final x calculations, and x values are extrapolated to the pure sample based on the concentrations of NLO materials in the solvent used. Other details of the experimental setup and calculations used to determine third-order nonlinear susceptibilities were given earlier and described in earlier publications [5,6,9,17-19]. 

In papers [6,7] it is reported that the orientational mechanism of nonlinearity of the LC oriented mesophase can cause very large values of nonlinear optical constants the constants of light amplification in the stimulated scattering in NLC [6] and in smectic LC [7]. The point is, that variations of the NLC director direction lead to very large changes of its optical properties, because = j[ - 0.5—1 (/i and are the... 

The optical properties of liquid crystals determine their response to high frequency electromagnetic radiation, and encompass the properties of reflection, refraction, optical absorption, optical activity, nonlinear response (harmonic generation), optical waveguiding, and light scattering [1], Most applications of thermotropic liquid crystals rely on their optical properties and how they respond to changes of the electric field, temperature or pressure. The optical properties can be described in terms of refractive indices, and anisotropic materials have up to three independent principal refractive indices defined by a refractive index ellipsoid. 

Khoo IC (1981) Optically induced molecular reorientation and third-order nonlinear optical processes in nematic liquid crystals. Phys Rev A 23(4) 2077-2081 Khoo IC (1982a) Nonlinear light scattering by laser- and dc-field-induced molecular reorientations in nematic-liquid-crystal films. Phys Rev A 25(2) 1040-1048 Khoo IC (1982b) Theory of optically induced molecular reorientations and quantitative experiments on wave mixing and the self-focusing of light. Phys Rev A 25(3) 1636-1644 Khoo IC (1995) Liquid crystals physical properties and nonlinear optical phenomena. Wiley, New York... 

In this chapter we begin to study optical phenomena which occur at surfaces or interfaces when the intensity of the incident light is weak. These phenomena include reflection, refraction and the scattering of light, as well as the excitation of coupled modes propagating along the surface or interface. The optical properties of media at the border, which determine these phenomena, are assumed to be independent of the light intensity. Nonlinear optical effects will be discussed in Chapter 6. 

A wide variety of techniques have been employed for the characterization of thin film samples of nonlinear polymeric materials. Many of these are similar to techniques described in the previous section for bulk material characterization, and are employed with thin film samples both to assess differences in material properties in the two physical forms and because certain measurements such as absorption or electro-optic effects may be more easily made in thin film samples. Other techniques are specific to thin film samples in which light can be guided, for which parameters can be measured having no bulk equivalent, such as waveguide scatter or nonlinear mode coupling. 

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