Nonlinear index of refraction

Figure 7-13. (a) Linear absorption of DOO-PPV, (b) imaginary part of ) (proportional to two-photon absorption), and (c) real part ol (proportional to the nonlinear index of refraction. .). 

The nonlinear index of refraction is related to the applied electric field, E, through the electric-field-dependent susceptibility, Xen of a material. 

A new interesting approach to air-pollution measurements is based on high-power terawatt femtosecond laser pulses that are sent into the atmosphere [1473]. The experimental setup is shown in Fig. 10.21. High intensities are reached in the focal area of the parabolic sending telescope due to self-focusing, which leads to air breakdown and the production of a high-temperature plasma (Fig. 10.22). The intensity-dependent nonlinear index of refraction... 

Another expression for the NLO phenomenon is the nonlinear index of refraction of the medium. When the medium is subjected to a dc field E(0) and an optical field E(o>), the total field to which the medium is subjected can be described as [2,10]... 

Values have been calculated for the nonlinear Index of refraction (arising from molecular reorientation and local spatial redistribution), the threshold power for self-focusing in the liquid (over periods so short that macroscopic density changes do not have time to take place), and the nonlinear index of Debye (for molecular reorientation alone) [11]. 

Applications Involving Nonlinear Index Phenomena. The index of refraction, n, can be expressed for nonlinear optical materials as... 

In this section, a problem of nonlinear waveguide excitation by stationary light beam has been investigated. In the analysis, an approach traditional for nonlinear optics and based on solution to nonlinear paraxial wave equation has been used. The range of light beam powers that induce nonlinear variation of refractive index comparable with linear contrast of the step-index waveguide has been considered. 

The difference this derivation has in comparison to the previous derivation of the nonlinear Schrodinger equation is that the nonlinearity is more fundamentally due to the non-Abelian wavefunction rather than from material coefficients. In effect these material coefficients and phenomenology behave as they do because the variable index of refraction is associated with non-Abelian electrodynamics. Ultimately these two views will merge, for the mechanisms on how photons interact with atoms and molecules will give a more complete picture on how non-Abelian electrodynamics participates in these processes. However, at this stage we can see that we obtain nonlinear terms from a non-Abelian electrodynamics that is fundamentally nonlinear. This is in contrast to the phenomenological approach that imposes these nonlinearities onto a fundamentally linear theory of electrodynamics. 

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