Susceptibility, optical

Gavrilenko V I and Rebentrost F 1995 Nonlinear optical susceptibility of the surfaces of silicon and diamond Surf. Sc/. B 331-3 1355-60... 

Neeves, A.E. and Birnboim, M.H. (1989) Composite structures for the enhancement of nonlinear-optical susceptibility. Journal of the Optical Society of America B - Optical Physics, 6, 787-796. 

Knoester, J. 1993. Nonlinear optical susceptibilities of disordered aggregates—A comparison of schemes to account for intermolecular interactions. Phys. Rev. 47 2083-2098. 

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... 

The first and third order terms in odd powers of the applied electric field are present for all materials. In the second order term, a polarization is induced proportional to the square of the applied electric field, and the. nonlinear second order optical susceptibility must, therefore, vanish in crystals that possess a center of symmetry. In addition to the noncentrosymmetric structure, efficient second harmonic generation requires crystals to possess propagation directions where the crystal birefringence cancels the natural dispersion leading to phase matching. 

Experimental Pitfalls. Several types of systematic inaccuracies in nonlinear optical susceptibility characterization techniques have appeared in the literature due to incomplete analysis of propagation effects. It is believed that use of the above models make them more obvious. Some examples are described in this section. 

Let us consider the crystal growth of the three previous compounds which have retained our attention by their high nonlinear optical susceptibilities (POM, MAP, NPP) plus an additional one R(+)N-methylidene (gem-carbethoxiphenyl) amide of 4-N-dime-thylamino- benzylidene cyanacetlc acid -AMA, of potential interest but not yet investigated from the optical point of view. We look successively into their synthesis, purification, crystal growth and characterization. 

There are different paths to achieving surface specificity. One can exploit optical susceptibilities and resonances that are nonzero only at the surface or only for the molecular species of interest adsorbed on the surface. Examples include the use of second-order nonlinear mixing processes such as second harmonic generation7-9 for which the nonlinear susceptibility tensor is nonzero only where inversion symmetry is broken. Spectroscopic techniques with very high selectivity for molecular resonances such as surface-enhanced infrared or Raman spectroscopy10-12 may also be used. 

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. 

The interest in efficient optical frequency doubling has stimulated a search for new nonlinear materials. Kurtz 316) has reported a systematic approach for finding nonlinear crystalline solids, based on the use of the anharmonic oscillator model in conjunction with Miller s rule to estimate the SHG and electro optic coefficients of a material. This empirical rule states that the ratio of the nonlinear optical susceptibility to the product of the linear susceptibilities is a parameter which is nearly constant for a wide variety of inorganic solids. Using this empirical fact, one can arrive at an expression for the nonlinear coefficients that involves only the linear susceptibilities and known material constants. 

The ability to perform simultaneous measurements of the TH on the interface and in the bulk of solution containing submicroscopic particles provides a very unique way of measuring the size of those particles and their nonlinear optical susceptibility (Shcheslavskiy et al. 2006a). Indeed, when such measurements are performed on the... 

The proper phase shift introduced to the signal wave allows direct measurements of the imaginary part of the resonant nonlinear optical susceptibility, i.e ... 

Shcheslavskiy, V., Petrov, G. I., and Yakovlev, V. V. 2003. Nonlinear optical susceptibility measurements in solutions using third-harmonic generation at interfaces. Appl. Phys. Lett. 82 3982-84. 

Hellwarth, R. W. 1977. Third-order optical susceptibilities of liquids and sohds. In Progress in quantum electronics, eds. J. H. Sanders, S. Stenholm, 1-68. New York Pergamon. 

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)... 

We have successfully demonstrated the concept of simultaneous polymerization and poling of photocrosslinkable systems to produce high quality films with large second-order nonlinear optical susceptibilities and low scattering losses. The ability to process these materials under mild conditions may help avoid potential problems encountered in... 

The basic structural units responsible for the second order nonlinear optical susceptibility in most oxide crystals are the acentric anionic groups. (4,6) The... 

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. 

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