Electro-optic scatter mode

Unlike ISS, the electro-optic effect (or its inverse) can occur only in noncentrosymmetric media and in general does not lead to any real material excitation. However, if there are low-frequency IR-active modes in the crystal, they may be excited impulsively [36, 59]. Such phonons couple strongly to IR radiation to form mixed modes called polaritons. Impulsive stimulated polariton scattering can be described approximately by coupled equations of motion for the polarization contributions P, and due to ionic motions (i.e., phonons) and electronic motions, respectively [9, 60] ... 

Figure 9. Oscillations of phonon-polariton mode in lithium tantalate crystal excited through inverse electro-optic effect and impulsive stimulated polariton scattering. Time-dependent birefringence measured with probe pulse, which propagated parallel to but not collinear with excitation pulse. (Reprinted with permission from ref. 36.)...

Fig. 9 Schematic illustration of hght scattering electro-optical switching of nematic LC gels (a) normal mode (b) reverse mode...

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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