Third-order nonlinear optical susceptibility

Dirk CW, Cheng L, Kuzyk MG (1992) A simplified three-level model describing the molecular third-order nonlinear optical susceptibility. Int J Quantum Chem 43 27-36... 

Kuzyk MG, Dirk CW (1990) Effects of centrosymmetry on the nonresonant electronic third-order nonlinear optical susceptibility. Phys Rev A 41 5098-5109... 

Aromatic poly(benzothiazole)s are thermally and thermooxidatively stable and have outstanding chemical resistance and third-order nonlinear optical susceptibility. Aromatic poly(benzothiazole)s can be spun into highly-oriented ultrahigh strength and ultrahigh modulus fibers. However, this type of polymer is insoluble in most organic solvents. Therefore, hexafluoroisopropylidene units are introduced in the polymer backbone to obtain soluble or processable aromatic poly(benzothiazole)s. 

The red PL band of PS can not only be excited by above bandgap photons, but also by an intense IR (1064 nm) pulse [Di6]. Such a thermostimulated luminescence is known for the case of glasses. This observation was attributed to PS having about 100 times the third-order nonlinear optical susceptibility of bulk Si, as discussed in Section 7.3. Multiphoton excitation of the red PL band by resonant pumping of the vibrational modes of surface groups like Si-O [Di4] or Si-H [Ch8] provided evidence for excitation modes that involve the porous skeleton surface. 

In Equation 1, x is the linear susceptibility which is generally adequate to describe the optical response in the case of a weak optical field. The terms x and X are the second and third-order nonlinear optical susceptibilities which describe the nonlinear response of the medium. At optical frequencies (4)... 

In a recent communication we reported that the third order nonlinear optical susceptibility of Pt, Pb, and H2 tetrakis(cumylphenoxy)phthalocyanines was large and varied substantially with the metal substituent. (1) The structure of these compounds is shown in Fig. 1. The susceptibility was measured by degenerate four-wave mixing at 1.064 pm, a wavelength far from the main absorption bands of phthalocyanines near 650 nm. The nonlinear susceptibility of the Pt phthalocyanine was about a factor of 9 larger than that of the Pb phthalocyanine and a factor of 45 larger than the metal free compound. 

On the route to all-optical signal processing the development of materials with large third-order nonlinear optical effects is of decisive importance. For the material characterization and the assessment of its usefulness for applications the absolute value of the third-order nonlinear optical susceptibility y has to be known. Since most measurements are performed relative to a reference material, the establishment of a well accepted value for a standard material is important. 

Fig. 5. Concentration series of a third-harmonic generation experiment. The third-order nonlinear optical susceptibilities of the solutions are analyzed with the solvent nonlinearity -Tchci f°r c = 0 and the slope dx ldc proportional to the second-order hyperpolarizability yof the molecule under investigation...

Another feature that sets the PDAs aside from other CPs is that most attempts at doping them have been unsuccessful. In the days where obtaining the highest (reversible) conductivity was a major goal, that was a severe drawback. On the other hand, PDAs have large third-order nonlinear optical susceptibilities, even compared to other CPs (in fact, this property of undoped CPs was discovered on a PDA in 1976 [55]), and this is presently an active field of study [56]. 

The first common method for molecular first hyperpolarizability determination is the electric field-induced second harmonic generation (EFISH) technique in solution [6-10]. This technique can be applied only to dipolar molecules. Under an applied external electric field, molecules in solution orient approximately in the direction of the field giving rise to second harmonic generation. The measured third-order nonlinear optical susceptibility is given by the following expression ... 

The same year, Levine [182] proposed a model that related the anharmonic motion of the bond charge, located approximately halfway between two neighboring atoms, to the second- and third-order nonlinear optical susceptibilities of... 

Liao, H.B., Xiao, R.F., Fu, J.S., Wong, G.K.L. Large third-order nonlinear optical susceptibility of AU-AI2O3 composite films near the resonant frequency. Appl. Phys. B 65, 673-676 (1997)... 

Hamanaka, Y., Fukuta, K., Nakamura, A., Liz-Marzan, L.M.. Mulvaney, P. Enhancement of third-order nonlinear optical susceptibilities in siUca-c ped Au nanoparticle films with very high concentrations. Appl. Phys. Lett. 84, 4938-4940 (2004)... 

The third-order nonlinear optical susceptibility x was obtained by comparing the measured signals for the sample with that of carbon disulfide as reference under the same experimental condition. The measured x value is 6.2 x 10 esu for the subphthalocyanine at a concentration 1.25 x 10 M. Considering an isotropic media under the Lorenz-Lorentz approximation, the second hyperpolarizability value was found to be 3.0 x 10 esu. Furthermore, A pirc corresponding to the pure subphthalocyanine 17 was calculated to be 6.9 x 10 esu, about four times higher... 

Sinclair and coworkersmeasured the third-order nonlinear optical susceptibility of rm 5 -polyacetylene. The measured susceptibility was 5 x 10 esu, which is comparable to the magnitude of the large nonlinear susceptibilities measured in the polydiacetylenes. 

FIGURE 15. Third-order nonlinear optical susceptibility spectra Im[x )(- 3co cd, cd, co)] in comparison with the exciton absorption spectra Reproduced by permission of... 

The temporal response of the third-order nonlinear optical susceptibility in poly(PTS) crystal was determined by time-resolved degenerate four-wave mixing (DFWM) by Carter and coworkers. The excited lifetime T ws measured to be 1.8 0.5 ps at 652 nm in the resonant region. The values of phase relxation time T2 measures by Hattori and Kobayashi for a cast film of poly(3BCMU) were 30 and 90 fs for the respective incident... 

Table 23. Third-Order Nonlinear Optical Susceptibilities of the Polymers ...

Three-Level Model Describing the Molecular Third-Order Nonlinear Optical Susceptibility. 

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