Anisotropic optical materials

A few remarks would be in order on the potentiality of metal-containing polymers as application-oriented materials. The major applications of these materials are in the following directions (a) electronic materials, anisotropic optical materials - active species in electronic energy-transfer processes of lasers... 

Liu, (., Cankurtaran, B., Wieczorek, L., Ford, M.J. and Cortie, M.B. (2006) Anisotropic optical properties of semitransparent coatings of gold nano-caps. Advanced Functional Materials, 16, 1457-1461. 

Anisotropic oriented materials consisting of aromatic acrylate acid esters, (V), were prepared by Saitoh et al. (5) and used in optical film. 

X-ray diffraction, electron diffraction and neutron diffraction all involve using radiations whose wavelengths are of the same order as the distances between the molecules. However, it is possible to obtain valuable information about the state of order of a thin organic film using radiations in the visible and infrared regions. A material which has anisotropic optical properties in the plane normal to the direction of the incident... 

In anisotropic materials, the electronic bonds may have different polarizabilities for different directions (you may think of different, orientation-dependent spring constants for the electronic harmonic oscillator). Remembering that only the E-vector of the light interacts with the electrons, we may use polarized light to test the polarizability of the material in different directions, lno is one of the most important electro-optic materials and we use it as an example. The common notations are shown in Figure 4.7. If the E-vector is in plane with the surface of the crystal, the wave is called a te wave. In this example, the te wave would experience the ordinary index na of LiNbOs (nG 2.20). If we rotate the polarization by 90°, the E-ve ctor will be vertical to the surface and the wave is called tm. In lno, it will experience the extraordinary index ne 2.29. Therefore these two differently polarized waves will propagate with different phase velocities v c/n. In the example of Figure 4.7, the te mode is faster than the tm mode. 

Optical—in particular spectral—studies play an important role in the investigation of electronically low-dimensional organic conductors. The materials are characterized by highly anisotropic optical properties, with one crystal direction often displaying metal-like behavior, while others appear to be lower conducting. Previous reviews of optical properties of these materials have been elaborated by numerous authors (e.g., Refs. 1 to 10). It was shown that optical studies provide information on a number of fundamental interactions and basic properties of organic conductors. 

A triumph of the Durham route was the preparation of oriented crystalline polyacetylene (107-109) by stretch orientation of the polymer during the transformation reaction. This material has highly anisotropic optical properties, but the anisotropy of the conductivity of the doped polymer was low. Oriented fibers as well as films were prepared. 

Since second-order nonlinear optical materials are anisotropic, their optical properties are described by tensors as discussed previously in Sect. 2.1.2. For a nonlinear optical process, the -th order nonlinear polarization is due to n interacting electric held vectors and is described by an (n -I-1) rank tensor composed of 3"+ tensor elements. In nonlinear optics, several fields with different frequencies l can be present simultaneously so that the electric field and the polarization are represented by... 

Nonopaque materials, those that allow the transmission of light, can be optically classified as "isotropic" or "anisotropic." Isotropic materials (e.g., oil, water, epoxy, crystals in the isometric system) transmit light in all directions at the same velocity. Anisotropic materials (e.g., alite, calcite, quartz, all crystals in systems other than the isometric) divide the light into... 

Figure 3.25. Thickness dependence of absorption depth (AT = 1 - T) for (a) vjox. P) vroy> and (c) VLQz bands in transmission spectra of standing film of anisotropic inorganic material (Table 3.3) at several angles of incidence (a, c) for p-polarization p) for s-polarization. Dashed lines are calculated according to thin-film approximation Equation (1.98). Reprinted, by permission, from K. Yamamoto and FI. Ishida, Appl. Opt. 34, 4177 (1995), p. 4181, Fig. 6. Copyright 1995 Optical Society of America.

In this section, only the optical constants of isotropic films determined by the multiwavelength approach in IRRAS will be discussed. The optical constants are assumed to be independent of the film thickness, and any gradient in the optical properties of the substrate (Section 3.5) is ignored. This undoubtedly lowers accuracy of the results. Anisotropic optical constants of a film are more closely related to real-world ultrathin films. At this point, it is worth noting that approaches to measuring isotropic and anisotropic optical constants are conceptually identical An anisotropic material shows a completely identical metallic IRRAS spectrum to the isotropic one if the complex refractive index along the z-direction for the anisotropic material is equal to that for the isotropic one [44]. However, to... 

Asahi T and Kohayashi J (2003) Polarimeter for anisotropic optically active materials. In Weiglhofer WS and Lakhtakia A (eds.) Introduction to Complex Mediums for Optics and Electromagnetics, pp. 645-676. Bellingham, WA SPIE Press. 

Since side-chain-type LC polyacetylene derivatives were first synthesized [10-18], various types of LC conjugated polymers have been synthesized and evaluated from the standpoint of their electrical and optical properties [19-46]. Among them, LC aromatic conjugated polymers, including LC polythiophene derivatives, have been of recent interest because they are available for linearly polarized luminescent materials, and also anisotropically conducting materials [28-30, 40-53]. 

Side-chain homopolymers based on poly(meth)acrylic derivatives (Fig. 16.14a) have been also widely studied (Andruzzief al., 1999 Rodriguez et al, 2005, 2006). When a suitable flexible spacer mediates between the main chain and the chromophore, these side chain polymers tend to exhibit thermotropic hquid crystalline properties, which favor cooperative chromophores motion during photoorientation and lead to more stable anisotropic optical properties. The azobenzene chromophore strongly influences a material s photoresponse. As a representative example, Ikeda... 

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