Third-order nonlinear susceptibilities measurement

The experimental technique used to measure the third order nonlinear susceptibilities of polydiacetylenes was developed recently at our laboratory. (15) This technique utilizes the intensity-dependent dispersion relation of confined modes of PDA films and determines by measuring the change of coupling angles with... 

Chen, Y. J. Carter, G. M. "Measurement of Third Order Nonlinear Susceptibilities by Surface Plasmons," Appl. Phys. 

Etchepare I, Grillon G, Antonetti A, Loulergue JC, Fontana MD, Kuge GE. Third-order nonlinear susceptibilities and polariton modes in PbTi03 obtained by temporal measurements. Phys Rev B 1990 41(17) 12362. 

Table 1. Intrinsic third-order nonlinear susceptibility of noble metal nanoparticles, through Eq. (27) from values measured on low-/ nanocomposite media...

When the pulse duration is much shorter than the nonlinear response time of the material (transient case), the third-order nonlinear susceptibility can be expressed in a phenomenological time-independent form similar to the one corresponding to the long-lasting pulse regime - the adiabatic case [68]. It is then a priori possible to compare the measurement results obtained in such opposite temporal regimes, provided the physical processes involved in the optical response remain exactly the same and, especially, are not intensity-dependent. This condition being fulfilled, the... 

The second-order molecular polarizability, /, and the third-order nonlinear susceptibility, have been measured for many compounds (see Table 5.7). Note that the f value of nitroaniline, where the centrosymmetric benzene ring carries an electron withdrawing nitro-group and an electron-donating amino-group, is larger than that of monosubstituted benzenes. 

Optical tuning of polygermanes and mixed polysi-lane/polygermane systems have been discussed.Nonlinear optical effects are of particular interest. Third-order nonlinear susceptibilities (/ ) for thin films of oligo- and polygermanes have been measured.A value of 86 x 10 esu was obtained for copoly(methyl-phenylsilylene/methylphenylgermylene)... 

The nonlinear optical (NLO) susceptibilities of bioengineered aromatic polymers synthesized by enzyme-catalyzed reactions are given in Tables 2, 3, and 4. Homopolymers and copolymers are synthesized by enzyme-catalyzed reactions from aromatic monomers such as phenols and aromatic amines and their alkyl-substituted derivatives. The third-order nonlinear optical measurements are carried out in solutions at a concentration of 1 mg/mL of the solvent. Unless otherwise indicated, most of the polymers are solubilized in a solvent mixture of dimethyl formamide and methanol (DMF-MeOH) or dimethyl sulfoxide and methanol (DMSO-MeOH), both in a 4 1 ratio. These solvent mixtures are selected on the basis of their optical properties at 532 nm (where all the NLO measurements reported here are carried out), such as low noise and optical absorption, and solubility of the bioengineered polymers in the solvent system selected. To reduce light scattering, the polymer solutions are filtered to remove undissolved materials, the polymer concentrations are corrected for the final x calculations, and x values are extrapolated to the pure sample based on the concentrations of NLO materials in the solvent used. Other details of the experimental setup and calculations used to determine third-order nonlinear susceptibilities were given earlier and described in earlier publications [5,6,9,17-19]. 

Nonlinear optical properties of homopolymers and copolymers synthesized by enzyme-catalyzed reactions in monophasic media are given in Table 2. Aromatic monomers used for the polymerizations are aniline, aniline derivatives, and phenol derivatives. The table also gives x values of a number of monomers (used in the polymerization reactions) and solvent mixtures used to prepare polymer solutions for the measurements. In general, the third-order susceptibilities of all monomers and solvents tested are very low and are in the neighborhood of 10" esu. The values of the aromatic polymers obtained are three to five orders higher than the values of the monomers. Third-order nonlinear susceptibilities of homopolymers synthesized (by enzyme-catalyzed reactions) from aromatic amines such as aniline, benzidine, ethylaniline, propylaniline, butylaniline, and dimethy-... 

The magnitude of the third-order nonlinear susceptibility, was estimated from a measurement of the intensity of the phase-conjugate beam relative to that of a reference sample of CS2 placed in a quartz cell of 2-mm path length. The value of was obtained from (22) ... 

In this paper we present some results of THG measurements in a solution of polydiacetylene at two laser wavelength 1.064 ym and 1.907 ym. The experimental arrangement, described elsewhere (6), allows not only an exact determination of third order nonlinear susceptibility, but also its phase. 

The third order optical susceptibility was measured for a series of transition metal tetrakis(cumylphenoxy)phthalocyanines at 1.064 pm. Metal substitution caused a dramatic variation in the third order susceptibility. The largest s were found in the Co, Ni, and Pt complexes. Metal substitution introduces low lying electronic states which can enhance the susceptibility in these phthalocyanines. A strategy for enhancing the figure of merit, x(3)/a> of centrosymmetric nonlinear optical materials is suggested. 

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. 

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 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. 

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... 

We measured third order nonlinear optical susceptibility for all the compounds in... 

In order to understand the origin of the high values of the third-order nonlinearity observed, we picked polybenzidine for more detailed study. The real and imaginary components of the third-order susceptibility x are measured separately. The real part Rex leads to nonlinear refraction, and the imaginary part Imx ) is responsible for nonlinear absorption. The nonlinear-optical measurements were made using dilute solutions of the polymer in DimethyLsulfoxide/Methanol in the ratio 4 1 (DMSO MeOH). 

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