Optical cavity with a double-layered cholesteric liquid crystal mirror and its prospective application to solid state laser

The authors have fabricated an optical cavity with silver (Ag) and double-layered cholesteric liquid crystal (CLC) mirrors facing each other. This CLC mirror consists of left-handed CLC and right-handed CLC films for high light reflection irrespective of polarization states. A single-mode lasing was observed in dye-doped CLC sandwiched between Ag and double-layered CLC mirrors. The authors also fabricated a flexible solid state device with a spin-coated dye molecular film sandwiched between Ag and double-layered CLC mirrors. Amplified spontaneous emission was observed from the solid state device, suggesting a possible structure for a flexible and tunable solid state laser.open

Unexpected electric-field-induced antiferroelectric liquid crystal phase in the Sm C*α temperature range and the discrete flexoelectric effect

The unique nanometer-sized helical structure in SmCα∗ may sometimes evolve continuously to the micrometer-sized one in SmC∗; conceivably ferroelectric SmCα∗ is to be unwound by an applied electric field. By drawing electric-field-induced birefringence contours in the field-temperature phase diagram and by studying the superlattice structure of the field-induced subphase with resonant x-ray scattering, we established that an applied field unexpectedly stabilizes the well-known antiferroelectric four-layer biaxial subphase as well as the other prototypal ferrielectric three-layer one in the SmCα∗ temperature range; the effective long-range interlayer interaction due to the discrete flexoelectric effect actually plays an important role in stabilizing not only the biaxial subphases but also the optically uniaxial SmCα∗ subphase, contrary to the notion that the competition between the direct interactions of the nearest-neighbor layers and those of the next-nearest-neighbor layers should be required for the nanometer-sized helical structure

Polarization characteristics of phase retardation defect mode lasing in polymeric cholesteric liquid crystals

We have studied the lasing characteristics of a dye-doped nematic layer sandwiched by two polymeric cholesteric liquid crystal (CLC) films as photonic band gap (PBG) materials. The nematic layer acts as a defect layer, the anisotropy of which brings about the following remarkable optical characteristics: (1) reflectance in the PBG region exceeds 50% due to the retardation effect, being unpredictable from a single CLC film; (2) efficient lasing occurs either at the defect mode wavelength or at the photonic band edge; and (3) the lasing emission due to both the defect mode and the photonic band edge mode contains both right- and left-circular polarizations, while the lasing emission from a dye-doped single CLC layer with a left-handed helix is left-circularly polarized.open2

Chiral Symmetry Breaking in Liquid Crystals: Appearance of Ferroelectricity and Antiferroelectricity

The study of chiral symmetry breaking in liquid crystals and the consequent emergence of ferroelectric and antiferroelectric phases is described. Furthermore, we show that the frustration between two phases induces a variety of structural phases called subphases and that resonant X-ray scattering is a powerful tool for the structural analysis of these complicated subphases. Finally, we discuss the future prospects for clarifying the origin of such successive phase transition

Analysis of the intralayer molecular orientation in the B1 phase of a bent-core liquid crystal molecule using X-ray microbeam(New Frontiers in Colloidal Physics : A Bridge between Micro- and Macroscopic Concepts in Soft Matter)

この論文は国立情報学研究所の電子図書館事業により電子化されました。アキラル屈曲型液晶のB1相構造に関して、X線マイクロビームでその配向解析を行った。結果、これまで提案されていた2つの構造のうち、Col(pm2_1m)の対称性を持つ屈曲面に垂直な面内に2次元周期構造を有することがわかった。Achiral bent-core liquid crystals are very interesting from a viewpoint of "chiralily" which appears in an "achiral" molecular system, and have been investigated experimentally and theoretically by many researchers. The bent-core molecules exhibit specific mesogenic phases, B1～B8, different from those in rod-like molecules. The determination of the structure in each phase is crucial but difficult, because of difficulties in obtaining large uniform domains. The B1 phase was found in P-6-O-PIMB (Fig. 1(a)). A two-dimensional (2D) modulated structure (Col(p2mg)) was proposed for the phase, as shown in Fig. 1(b), based on macroscopic x-ray diffraction. On the other hand, another 2D structure (Col(pm2, m)) shown in Fig. 1(c) has been very recently proposed in the other compound

Dynamic heterogeneity of a nanostructure in the hyper-swollen B4 phase of achiral bent-core molecules diluted with rod-like liquid crystals

We studied the dynamics in the chiral mesogenic phases observed in binary mixtures of 5CB and bent-core molecules by using dynamic light scattering. In the lower-temperature phase, a clear orientational fluctuation was observed, which was not observed in the higher-temperature one. The wave number dependence of the relaxation frequency strongly indicates that nanoscale phase separation occurs and that the fluctuations of 5CB with nematic order are suppressed by the bent-core–rich domains. The spatial heterogeneity of the nematic dynamic motion yields exact information on the characteristic size of the nanostructure, which cannot be obtained by static structural analysis