Susceptibilities third-order

For each EA spectrum, the transmission T was measured with the mechanical chopper in place and the electric field off. The differential transmission AT was subsequently measured without the chopper, with the electric field on, and with the lock-in amplifier set to detect signals at twice the electric-field modulation frequency. The 2/ dependency of the EA signal is due to the quadratic nature of EA in materials with definite parity. AT was then normalized to AT/T, which was free of the spectral response function. To a good approximation [18], the EA signal is related to the imaginary part of the optical third-order susceptibility ... 

The term nonlinear optical property refers to an optical property, which can be modified by exposing the material to intense light irradiation. In this section, we focus on the cascaded first- (/ 1 ) and third-order ( / ) susceptibilities describing nonlinear absorption (ESA and 2PA) and nonlinear refraction (n2) processes. Z-scan, pump-probe, and two-photon upconverted fluorescence techniques are among the most used experimental methods for determining optical nonlinearities. 

Three Wave Mixing. A number of resonances are possible in the third-order susceptibility, These resonances may be due to... 

The large values of the hyperpolarizability in these molecules imply large susceptibilities for more concentrated solutions or solid-state films. This large third-order susceptibility can... 

Polyarylenevinylene (PAV) expressed by the chemical formula of [-Ar-CH=CH-]n, where Ar is an arylene ring, is an attractive n-conjugated polymer family because of the following features (i) by the thermal conversion from polyelectrolyte or organic-solvent-soluble precursors, one can obtain the PAV films which have large third-order susceptibility and excellent optical quality, and (ii) the band gap can be adjusted by suitable selection of the arylene rings. 

Third-order susceptibilities of the PAV cast films were evaluated with the third-harmonic generation (THG) measurement [31,32]. The THG measurement was carried out at fundamental wavelength of 1064 nm and between 1500 nm and 2100 nm using difference-frequency generation combined with a Q-switched Nd YAG laser and a tunable dye laser. From the ratio of third-harmonic intensities I3m from the PAV films and a fused quartz plate ( 1 thick) as a standard, the value of x(3) was estimated according to the following equation derived by Kajzar et al. [33] ... 

Figure 27 shows spectra of third-order susceptibility x(3) of the oriented MOPPV LB film. Owing to the orientation of MOPPV chains, anisotropy of x(3) was observed. The x(3) values of the LB film, which is enhanced by the three photon resonance, are maximized at a fundamental wavelength of 1600 nm, as observed in a MOPPV cast film. The maximum values of X ( 3) and are 3.2 x 10 10 esu... 

The combination of organic dopants with oriented assemblies of organic compounds with high-order nonlinear polarization or organic substances of large third-order susceptibility, x , with inorganic sol-gel matrices, offers a greatly expanded capability for... 

Characterization of Molecular Hyperpolarizabilities Using Third Harmonic Generation. Third harmonic generation (THG) is the generation of light at frequency 3co by the nonlinear interaction of a material and a fundamental laser field at frequency co. The process involves the third-order susceptibility x 3K-3 , , ) where —3 represents an output photon at 3 and the three s stand for the three input photons at . Since x(3) is a fourth (even) rank tensor property it can be nonzero for all material symmetry classes including isotropic media. This is easy to see since the components of x(3) transform like products of four spatial coordinates, e.g. x4 or x2y2. There are 21 components that are even under an inversion operation and thus can be nonzero in an isotropic medium. Since some of the terms are interrelated there are only four independent terms for the isotropic case. 

The reflectivity of the doped gel was found to be 31% of that from the CS2 reference. Assuming that the third-order susceptibility of carbon disulfide is 1.7 x 10 ... 

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. 

This paper is a more extensive survey of the influence of the metal on the hyperpolarizability of a series of the transition metal tetrakis(cumylphenoxy)-phthalocyanines (MPcCP4). The compounds chosen were those most closely related to PtPcCP4, the compound which showed the largest hyperpolarizibility in the previous study. Specifically, phthalocyanines substituted with the last four members of the first row transition metal series (Co, Ni, Cu, and Zn) and also with the Ni, Pd, Pt triad were prepared and studied. The near IR spectra of these tetrakis(cumylphenoxy)-phthalocyanines are briefly discussed. Speculation on how metal substitution can influence the third order susceptibility of a near centrosymmetric structure, like that of the phthalocyanines, is presented. 

The data in Table 1 reveal systematic variations in the measured third order susceptibilities of these phthalocyanines with the metal. There is a monotonic variation of y in the series Co, Ni, Cu, Zn. The nonlinear susceptibility decreases as the d orbitals of the metal become filled. There is also a qualitative correlation between a large hyperpolarizibility and the presence of a weak, near IR transition. However, the variation of the figure of merit, x(3)/ , shows that the correlation between y and the absorption coefficient is not linear. No clear trend is seen in the triad Ni, Pd, Pt although PtPcCP4 does have a larger hyperpolarizibility as might be expected for a larger, more polarizable metal ion. 

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