Second harmonic generation polymers

The value of 3 and its dispersion for a molecule, or polymer chain, can be experimentally determined by DC induced second harmonic generation (DCSHG) measurements of liquid solutions -1 2). The experimental arrangement requiring an applied DC field E° to remove the natural center of inversion symmetry of the solution is described in Figure 4. The second harmonic polarization of the solution is expressed as... 

Experimental and theoretical results are presented for four nonlinear electrooptic and dielectric effects, as they pertain to flexible polymers. They are the Kerr effect, electric field induced light scattering, dielectric saturation and electric field induced second harmonic generation. We show the relationship between the dipole moment, polarizability, hyperpolarizability, the conformation of the polymer and these electrooptic and dielectric effects. We find that these effects are very sensitive to the details of polymer structure such as the rotational isomeric states, tacticity, and in the case of a copolymer, the comonomer composition. 

We have shown in this paper the relationships between the fundamental electrical parameters, such as the dipole moment, polarizability and hyperpolarizability, and the conformations of flexible polymers which are manifested in a number of their electrooptic and dielectric properties. These include the Kerr effect, dielectric polarization and saturation, electric field induced light scattering and second harmonic generation. Our experimental and theoretical studies of the Kerr effect show that it is very useful for the characterization of polymer microstructure. Our theoretical studies of the NLDE, EFLS and EFSHG also show that these effects are potentially useful, but there are very few experimental results reported in the literature with which to test the calculations. More experimental studies are needed to further our understanding of the nonlinear electrooptic and dielectric properties of flexible polymers. 

Direct Evidence of Failure of Electric Dipole Approximation in Second-Harmonic Generation from Chiral Polymer Film... 

Figure 2 shows the tradeoffs between crystal and polymer organic NLO materials for device applications. Although cither type of materials could in principle be used for both applications, crystals are best for second harmonic generation, and poled polymers are best for electro-optic waveguide devices such as modulators and switches. 

The nonlinear optical properties of thin films of the polymers were investigated through measurement of second-harmonic generation, and exhibit second-harmonic coefficients, d33, in the range 4.1-34 pm/V. 

The high viscosity of the PMMA damps out orientational contributions so that the yqeo that is measured is thought to be =60-90% electronic. This has been ascertained by measuring the electric field induced second harmonic generation (EFISH) below the Tg of the polymer. From this can be obtained the microscopic elastic constant, which can in turn be used to estimate the magnitude of the two orientational contributions to yQEO- Details are provided else where (13,16). 

Amino-5-nitropyrimidine, cocrystallization, 455 Amorphous polymers, criteria for use in second harmonic generation, 250-251 Amphiphilic molecules polar Z-type Langmuir-Blodgett films, formation, 473-479 structures, transfer behavior, and contact angles, 474,476-477r Anharmonic oscillator models, nonlinear optical effect-microstructure relationship, 361... 

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