Optical Features

As has been mentioned in Section 1.1.3, there exist three thermodynamically stable blue phases BP I, BP II, and BP III (or foggy phase). The structure of the former two is already established, BP I is a body-centered cubic phase (symmetry group O or I4i(32) and BP II is a simple cubic 

FIGURE 6.24. Selective reflections versus temperature in the cholesteric BP I and BP II phases of CB15-E9 mixture (42-58%). (3 = tt/4 for the (110) curve, P = 7t/2 for all other curves. Wavelengths of reflection maxima are normalized to 1.6/n (BP I supercools below 42.1 °C) [94]. 

The three-dimensional crystalline structure of blue phases with lattice periods comparable to the wavelength of visible Ught results in the optical diffraction dependent on the orientation of the light wave vector with respect to the crystalline planes [93]. Thus, the selective reflection of light occurs in a different spectral range for different experimental geometry. This is well illustrated by Fig. 6.24 taken from [94] where selective reflection maxima (normalized to 1.6n) 

The most pronounced features of the optics of blue phases BP I and BP II axe [93]  

The optical properties of blue phases are completely defined by the tensor of the high-frequency dielectric permittivity [93] 

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Superimposed on the Maltese cross may be such additional optical features as the banding seen in Fig. 4.12. 

Sundar VC, Yablon AD, Grazul JL et al (2003) Fibre-optical features of a glass sponge -some superior technological secrets have come to light from a deep- sea organism. Nature 424 899-900... 

The spectroscopy and dynamics of photosynthetic bacterial reaction centers have attracted considerable experimental attention [1-52]. In particular, application of spectroscopic techniques to RCs has revealed the optical features of the molecular systems. For example, the absorption spectra of Rb. Sphaeroides R26 RCs at 77 K and room temperature are shown in Fig. 2 [42]. One can see from Fig. 2 that the absorption spectra present three broad bands in the region of 714—952 nm. These bands have conventionally been assigned to the Qy electronic transitions of the P (870 nm), B (800 nm), and H (870 nm) components of RCs. By considering that the special pair P can be regarded as a dimer of two... 

The vibrational frequency of the special pair P and the bacteriochlorophyll monomer B have also been extracted from the analysis of the Raman profiles [39,40,42,44,51]. Small s group has extensively performed hole-burning (HB) measurements on mutant and chemically altered RCs of Rb. Sphaeroides [44,45,48-50]. Their results have revealed low-frequency modes that make important contribution to optical features such as the bandwidth of absorption line-shape, as well as to the rate constant of the ET of the RCs. 

The optical properties of semiconductor QDs (Fig. la-c, Tables 1 and 2) are controlled by the particle size, size distribution (dispersity), constituent material, shape, and surface chemistry. Accordingly, their physico-chemical properties depend to a considerable degree on particle synthesis and surface modification. Typical diameters of QDs range between 1 and 6 nm. The most prominent optical features of QDs are an absorption that gradually increases toward shorter... 

The exploration of biomolecules as components in CNT-based systems is a rapidly flourishing research field. The combination of the CNTs electronic and optical features with those of many biomolecules is appealing for many applications in medicine, optical device technologies and other fields. 

The optical features of a center depend on the type of dopant, as well as on the lattice in which it is incorporated. For instance, Cr + ions in AI2O3 crystals (the ruby laser) lead to sharp emission lines at 694.3 nm and 692.8 nm. However, the incorporation of the same ions into BeAl204 (the alexandrite laser) produces a broad emission band centered around 700 nm, which is used to generate tunable laser radiation in a broad red-infrared spectral range. 

Instead of considering how the incorporation of a dopant ion perturbs the electronic structure of the crystal, we will face the problem of understanding the optical features of a center by considering the energy levels of the dopant free ion (i.e., out of the crystal) and its local environment. In particular, we shall start by considering the energy levels of the dopant free ion and how these levels are affected by the presence of the next nearest neighbors in the lattice (the environment). In such a way, we can practically reduce our system to a one-body problem. 

The development of novel optical devices requires suitable materials which have the required chemical and photochemical stability, with appropriate optical features, which can also be made into usable forms such as thin films and bulk pieces. Since the sol-gel process9,10,218 219 offers a very attractive possibility with the ability to incorporate organic materials in inorganic matrices at low temperatures in the form of monolithic glasses or thin films, it has opened the way to many possible applications in optics1,60,190,192,193,196,220-222 and electrooptics2,223,224. 

The photonic force microscope may yield a means for proximal probe imaging within fluid-containing voids and structures such as vesicles and living cells. Some current limitations of the photonic force microscope include the potential for incorporation of optical artifacts when internal structures of optically complex samples (such as cells) are to be studied. Coupling of optical features into the images of such a microscope arises via the dependence of the optical trapping... 

A. Optical features and exchange coupling for structurally defined binuclear copper(II) complexes... 

B. Optical features of structurally defined mononuclear copper(II) phenolate complexes Complex Cu+2 Geometry CT(nm)a d-d(Alna,)(nm)a Ref. 

Boland, J. N., McLaren, A. C., Hobbs, B. E. (1971). Dislocations associated with optical features in naturally-deformed olivine. Contrib. Mineral. Petrol., 30, 53-63. 

Cholesteric liquid crystals are similar to smectic liquid crystals in that mesogenic molecules form layers. However, in the latter case molecules lie in two-dimensional layers with the long axes parallel to one another and perpendicular or at a uniform tilt angle to the plane of the layer. In the former molecules lie in a layer with one-dimensional nematic order and the direction of orientation of the molecules rotates by a small constant angle from one layer to the next. The displacement occurs about an axis of torsion, Z, which is normal to the planes. The distance between the two layers with molecular orientation differing by 360° is called the cholesteric pitch or simply the pitch. This model for the supermolecular structure in cholesteric liquid crystals was proposed by de Vries in 1951 long after cholesteric liquid crystals had been discovered. All of the optical features of the cholesteric liquid crystals can be explained with the structure proposed by de Vries and are described below. 

Recently in the field of physics of semiconductors and materials science a great attention has been paid to formation and optical properties of semiconductor nanocrystals (quantum dots, QDs) dispersed in inorganic matrixes. An interest to glassy materials with QDs is associated with their unique physical properties and possibility to create elements of optoelectronic devices. Phase separation processes followed by crystallization are the basic in production of such materials. They result in formation of semiconductor nanocrystals stabilized within a glass matrix. The materials are advanced for various applications because of optical and thermal stability and possibility to control optical features through the technology of glass preparation and post-synthesis thermal treatment. 

CeTi-doped silicate glasses demonstrate the controllable optical features with coloring in the yellow-orange range that is of interest for selective filters of signal lamps. The structural and optical studies argue on the nature of color centers formed on the basis of Ce-Ti-binary oxide nanophases stabilized within the glass matrix. 

The common optical features described above may be realized in different ways in the actual hardware design of a powder diffractometer goniostats and thus, goniometers differ from one another by ... 

AuNPs have been considered suitable for in vivo studies, due to well-known characterized biocompatibility. For AuNPs, many different strategies have been described for surface functionalization with drugs, peptides, and so on, which are very useful to perform systematic cytotoxic studies. AuNPs are used in proteomics because of its physicochemical properties (e.g., optical features, electromagnetic or photothermal properties), which are very useful for label-based detection methods (23,24). 

Ordered macroporous materials have special optical features due to their pore diameters. Since the synthesis of macroporous materials has just started, there are no general synthetic strategies for this type of materials at present, and hence only a few examples will be mentioned here. 

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