Blue phase optical property

PolyTCDU (X = C5H5) can be synthesized so that the red, high-temperature phase is stable at room temperature (12). Conversion to the blue phase can be achieved at low temperatures (at least partially) (13) or under a strain field (14). The optical properties of the red aTi blue phases of polyTCDU are nearly identical to those of polyETCD and polylUPDO (9,J ). The X-ray structure of polyTCDU (2 ) suggested that thTs polymer existed in the butatriene conformation, -(R)C C=C=C(R)-, rather than the commonly observed (and theoretically more stable) acetylenic conformation, =(R)C-C5C-C(R)=. This led to the suggestion that thermochromism involved an acetylenic-to-butatrienic conformational change (10). 

Recent progress in material science, notably with the development of new materials exhibiting blue phases, has generated a renewed interest in the incorporation of the functional properties with the unique structure of frustrated phases. Synthesis of a monosubstituted ferrocene-based chiral Schiff s base derivative which exhibits TGBA and blue phases has been reported [17] (Fig. 9). Other metallomesogens leading to blue phases have been found for palladium complexes [18] (Fig. 10). Optically active materials incorporating... 

As a consequence of an improved technology (higher and cleaner vacua, faster deposition rate), the newer films, possibly containing less oxygen, clearly show better optical values, especially in the blue and near ultraviolet region. Also, many other metal films are very sensitive to oxidation, and even traces of oxide-phases produce a degradation of their optical properties. 

The concept of defects came about from crystallography. Defects are dismptions of ideal crystal lattice such as vacancies (point defects) or dislocations (linear defects). In numerous liquid crystalline phases, there is variety of defects and many of them are not observed in the solid crystals. A study of defects in liquid crystals is very important from both the academic and practical points of view [7,8]. Defects in liquid crystals are very useful for (i) identification of different phases by microscopic observation of the characteristic defects (ii) study of the elastic properties by observation of defect interactions (iii) understanding of the three-dimensional periodic structures (e.g., the blue phase in cholesterics) using a new concept of lattices of defects (iv) modelling of fundamental physical phenomena such as magnetic monopoles, interaction of quarks, etc. In the optical technology, defects usually play the detrimental role examples are defect walls in the twist nematic cells, shock instability in ferroelectric smectics, Grandjean disclinations in cholesteric cells used in dye microlasers, etc. However, more recently, defect structures find their applications in three-dimensional photonic crystals (e.g. blue phases), the bistable displays and smart memory cards. 

Because the optical properties of blue phases are of great importance, we choose the traceless... 

The optical properties of the blue phase that interest us here are the transmittance and reflectance of the material and its effect on the polarization of light These properties depend on the dielectric tensor (at optical frequencies) of the material. The dielectric tensor e is related to the... 

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

Phase Change Materials (PCMs) are nowadays widely used for data recording and increasingly present non-volatile memories [1, 2]. Since Ovshinsky s precursor work [3], PCMs have been studied extensively, both experimentally [4-6] or with ab initio calculations [7-11], The operating principle of PCMs is based on the easy and reversible switching between the crystalline (C) and amorphous (A) states, each phase possessing very different electrical and optical properties. These materials are nowadays found in commercial applications for optical information storage and dissemination, such as CD-RW, DVD-RW or Blue-Ray disk, and could be used for the achievement of PC-RAM. 

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