Second-order optical nonlinearity

COPET technique, 391 optical nonlinearity second order, 390 third order, 394... 

Marek, Organometallic Complexes in Nonlinear Optics 1 Second-Order Non-... 

Nonlinear second order optical properties such as second harmonic generation and the linear electrooptic effect arise from the first non-linear term in the constitutive relation for the polarization P(t) of a medium in an applied electric field E(t) = E cos ot. 

The first and third order terms in odd powers of the applied electric field are present for all materials. In the second order term, a polarization is induced proportional to the square of the applied electric field, and the. nonlinear second order optical susceptibility must, therefore, vanish in crystals that possess a center of symmetry. In addition to the noncentrosymmetric structure, efficient second harmonic generation requires crystals to possess propagation directions where the crystal birefringence cancels the natural dispersion leading to phase matching. 

Organometallic Complexes in Nonlinear Optics I Second-Order Nonlinearities. 42 291... 

Teng, C.C. and Garito A.F., Dispersion of the nonlinear second-order optical susceptibility of organic systems. Phys. Rev. B (1983) 28 6766-6773. 

Electrostatic layer-by-layer (LBL) self-assembly techniques based on oppositely charged poipelectrolytes can be useful to create stable noncentrosymmetric order in thin films. Using this interesting technique, thermodynamically stable noncentrosymmetric multilayer films can be prepared without any need for poling. Tripathy et al. reported the fabrication stable multilayer films of epoxy-based side chain azo polymers for second-order nonlinear optics.The second-order NLO coefficients of the five-bilayer LBL films of these polymers were found to be comparable to those of spin-coated poled films. A schematic view of the procedure to fabricate polyelectrolyte-based LBL films is shown in Fig. 7. 

Nonlinear Optical Applications. Second-order nonlinear (NLO) materials based on ElAPs have shown promise for use in the photonics industry extensive research has been conducted in this area over the past several decades (356,357). Devices based on poly(diacetylene) have been used to demonstrate all-optical switching at 1.6 tm (358). The NLO process occurs when an electromagnetic field interacts with a medium. When the medium is subjected to an electric field E(0) and an optical field E(co), the nonlinear effect arises from field-induced... 

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