Circular dichroism nonlinear optics

Especially for the application to biological relevant surfaces (e.g., adsorbed proteins) the sensitivity of polarized SHG to the chirality of the molecules (the "handedness" of their structures) is important (Verbiest et al. 1998). Recently, the second-order nonlinear optical analog to circular dichroism and optical rotatory dispersion spectroscopy has been successfully developed (Yee et al. 1994 Byers et al. 1994). 

Optical properties of cyanines can be usefiil for both chiral substituents/environments and also third-order nonlinear optical properties in polymer films. Methine-chain substituted die arbo cyanines have been prepared from a chiral dialdehyde (S)-(+)-2-j -butylmalonaldehyde [127473-57-8] (79), where the chiral properties are introduced via the chiral j -butyl group on the central methine carbon of the pentamethine (die arbo cyanine) chromophore. For a nonchiral oxadicarbocyanine, the dimeric aggregate form of the dye shows circular dichroism when trapped in y-cyclodextrin (80). Attempts to prepare polymers with carbocyanine repeat units (linked by flexible chains) gave oligomers with only two or three repeat units (81). However, these materials... 

In order to describe the problems of the nonlinear optical response from biological systems, the question of chirality must be addressed. Linear circular dichroism (CD) has been investigated extensively for biological compounds and a wealth of data are available on... 

The systems discussed up to now all showed chiral susceptibilities that were of the same order of magnitude or smaller than the achiral susceptibility components. The system that we discuss in this section has chiral susceptibilities that dominate the nonlinear optical response.53 The material is a chiral helicenebisquinone derivative shown in Figure 9.22. In bulk samples, the nonracemic, but not the racemic, form of the material spontaneously organizes into long fibers clearly visible under an optical microscope. These fibers comprise columnar stacks of helicene molecules.54,55 Similar columnar stacks self-assemble in appropriate solvents, such as n-dodecane, when the concentration exceeds 1 mM. This association can be observed by a large increase in the circular dichroism (CD) of the solutions. 

Nonlinear optical activity phenomena arise at third-order and include intensity dependent contributions to optical rotation and circular dichroism, as well as a coherent form of Raman optical activity. The third-order observables are - like their linear analogs - pseudoscalars (scalars which change sign under parity) and require electric-dipole as well as magnetic-dipole transitions. Nonlinear optical activity is circular differential. 

In the case of degenerate four-wave mixing, i.e. m = m + u> — u>, a nonlocal may support nonlinear optical activity and thus intensity dependent contributions to optical rotation and circular dichroism [4, 13, 17-19]. In analogy to Eq. (8) we can include nonlinear optical activity phenomena by writing [4]. 

Various optoelectronic and related properties of polymers from mono-substituted acetylene monomers have been studied extensively, such as photoconductivity, nonlinear optical properties, photo and electroluminescence, electrochromism, liquid-crystalline structures, helical structures, and stimuli-responsiveness [2, 3, 6, 7]. It is noteworthy that helical structures and stimuli-responsiveness using the change of the helical structure have progressed considerably in this decade [20, 21]. Yashima s induced circular dichroism... 

J. Lu, L. Wu, L. Jing, X. Xu, X. Zhang, Synthesis, circular dichroism, and third-order nonlinear optical properties of optically active poiphyrin derivatives bearing four chiral citronellal moieties. Dyes Pigm. 94, 169-174 (2012)... 

Magnetic Circular Dichroism, Theory Nonlinear Optical Properties... 

See also Biomacromolecular Applications of Circular Dichroism and ORD Chiroptical Spectroscopy, Emission Theory Chiroptical Spectroscopy, General Theory Chiroptical Spectroscopy, Oriented Molecules and Anisotropic Systems Circularly Polarized Luminescence and Fluorescence Detected Circular Dichroism Light Sources and Optics Luminescence, Theory Nonlinear Optical Properties Vibrational CD Spectrometers Vibrational CD, Applications Vibrational CD, Theory. 

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