Electro-optical properties nonlinear

Barium sodium niobium oxide [12323-03-4] Ba2NaNb 02, finds appHcation for its dielectric, pie2oelectric, nonlinear crystal and electro-optic properties (35,36). It has been used in conjunction with lasers for second harmonic generation and frequency doubling. The crystalline material can be grown at high temperature, mp ca 1450°C (37). 

Liao, Y. Anderson, C. Y. Sullivan, P. A. Akelaitis, A. J. P. Robinson, B. H. Dalton, L. R., Electro optical properties of polymers containing alternating nonlinear optical chromophores and bulky spacers, Chem. Mater. 2006, 18, 1062 1067... 

It follows from the preceding results that the electro-optical properties of molecules in degenerate electronic states should have unusual temperature dependence, which is absent in the case of nondegenerate states. Even for nondipolar degenerate electronic states (e.g., for states in which the reduced matrix elements of the dipole moment are zero) for certain relationships between the vibronic constant and the temperature, there may be a quadratic dependence of the Kerr effect on p, similar to that observed in the case of molecules that are simultaneously anisotropic polarizable and possess a proper dipole moment. The nonlinear dependence on p under consideration is due exclusively to the vibronic interaction that redetermines the vibronic spectrum and leads to different polarizability in different vibronic states. This dependence on p has to be distinguished from that which arises due to the nonzero value of the dipole moment in the initial ground electronic state (e.g., as in the case of the E term in molecules with D3h symmetry). The two sources of the... 

To understand and optimize the electro-optic properties of polymers by the use of molecular engineering, it is of primary importance to be able to relate their macroscopic properties to the individual molecular properties. Such a task is the subject of intensive research. However, simple descriptions based on the oriented gas model exist [ 20,21 ] and have proven to be in many cases a good approximation for the description of poled electro-optic polymers [22]. The oriented gas model provides a simple way to relate the macroscopic nonlinear optical properties such as the second-order susceptibility tensor elements expressed in the orthogonal laboratory frame X,Y,Z, and the microscopic hyperpolarizability tensor elements that are given in the orthogonal molecular frame x,y,z (see Fig. 9). 

Before we proceed with specific device designs and fabrication techniques, we need to review the electro-optic properties of nonlinear optical polymers and the physics of electro-optic modulation and directional coupling. 

Because of the extensive overlap with electro-optics and nonlinear optics, the reader is referred to separate articles on these topics in this encyclopedia. See ElectroopticAL Applications for a discussion of the changes in the optical response of polymers dne to an applied AC or DC electric field from the so-called Pockels or Kerr effects. Also see, for an overview. Nonlinear Optical Properties. 

Experimentally, Tca Tc a and rclA found to be veiy close to one another. This is expected as the chital terms in the fiee-eneigy expression are basically small-peituibation terms. Their optical and electro-optical properties, however, are considerably modified by the presence of the chirality and spontaneous polarizatioir As we remarked earlier, ferroelectric liquid crystals provide a faster electro-optical switching mechanism. In the corrtext of nonlinear optics, the noncerrtrosyrrrmetry carrsed by the presence of P allows the generation of even harmorric light. 

Certain glass-ceramic materials also exhibit potentially useful electro-optic effects. These include glasses with microcrystaUites of Cd-sulfoselenides, which show a strong nonlinear response to an electric field (9), as well as glass-ceramics based on ferroelectric perovskite crystals such as niobates, titanates, or zkconates (10—12). Such crystals permit electric control of scattering and other optical properties. 

Crystals with one of the ten polar point-group symmetries (Ci, C2, Cs, C2V, C4, C4V, C3, C3v, C(, Cgv) are called polar crystals. They display spontaneous polarization and form a family of ferroelectric materials. The main properties of ferroelectric materials include relatively high dielectric permittivity, ferroelectric-paraelectric phase transition that occurs at a certain temperature called the Curie temperature, piezoelectric effect, pyroelectric effect, nonlinear optic property - the ability to multiply frequencies, ferroelectric hysteresis loop, and electrostrictive, electro-optic and other properties [16, 388],... 

Nonlinear Electro-optic and Dielectric Properties of Flexible Polymers... 

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