Blue phases are types of liquid crystal phases that appear in a temperature range between a chiral nematic phase and an isotropic liquid phase. Because blue phases have a three-dimensional cubic structure with lattice periods of several hundred nanometres, they exhibit selective Bragg reflections in the range of visible light corresponding to the cubic lattice. From the viewpoint of applications, although blue phases are of interest for fast light modulators or tunable photonic crystals, the very narrow temperature range, usually less than a few kelvin, within which blue phases exist has always been a problem. Here we show the stabilization of blue phases over a temperature range of more than 60 K including room temperature (260–326 K). Furthermore, we demonstrate an electro-optical switching with a response time of the order of 10−4 s for the stabilized blue phases at room temperature.

Polymer-stabilized liquid crystal blue phases

An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor device, and manufacturing method thereof

An object of the present invention is to decrease the resistance of a power supply line, to suppress a voltage drop in the power supply line, and to prevent defective display. A connection terminal portion includes a plurality of connection terminals. The plurality of connection terminals is provided with a plurality of connection pads which is part of the connection terminal. The plurality of connection pads includes a first connection pad and a second connection pad having a line width different from that of the first connection pad. Pitches between the plurality of connection pads are equal to each other.

Semiconductor device and display device

To provide a semiconductor device and a display device which can be manufactured through a simplified process and the manufacturing technique. Another object is to provide a technique by which a pattern of wirings or the like which is partially constitutes a semiconductor device or a display device can be formed with a desired shape with controllability.

Semiconductor device, electronic device, and method of manufacturing semiconductor device

Two types of photomodulation of orientations of liquid crystals (LCs) are reviewed: 1) order–disorder phase transitions of LCs induced by photochemical reactions of photochromic molecules and 2) order–order alignment change of LCs (change in LC directors) induced by photochemical reactions or without photochemical events. Both processes produce a large refractive-index modulation, which forms the basis of a range of photonic applications. Various modes of photomodulation of orientations of LCs with plausible mechanisms and their possible applications in photonics are described.

Photomodulation of liquid crystal orientations for photonic applications

We report the first observation of cholesteric blue phases in chiral anisotropic polymer networks. In two-component mixtures of a chiral and a non-chiral diacrylate, we observed typical textures of BPI, BPII and BPIII phases. By photopolymerization of these materials at constant temperature we obtained blue phase networks. After polymerization, the blue phases were stored, which enabled us to further study them without any temperature control.

Observation of blue phases in chiral networks

We succeeded in storing optical information with low-molecular-weight cholesteric liquid crystals. Nematic mixtures of glassy compounds which are chiralized by the addition of small amounts CB15 (BDH) have been used. Reversible optically induced holographic gratings were stored both below the glass transition temperature and above the glass transition in the temperature region of high viscosity. Erasure can be achieved by local heating of the sample making possible to use the material for multiple storage processes. A mechanism to explain the formation of the grating is discussed.

Storage of erasable laser induced holographic gratings in low molar mass cholesteric liquid crystals

We demonstrate that low molar mass discotic liquid crystals can be used for holographic storage. Grating structures are optically induced and stored in the glassy state of the investigated liquid crystal. The material is suitable for multiple storage processes since the stored information can be erased by heating the sample above the glass transition temperature.

Storage of laser-induced holographic gratings in discotic liquid crystals

We report on a novel ferroelectric liquid-crystal material with an exceptionally large and stable nonlinear optical response. The material shows a phase transition from theSmC* mesophase to the glassy state near room temperature. This allowed us to state-freeze a stable nonlinear optically active configuration close to room temperature at 10° C for one day. The stored orientations can easily be forced to relax back by heating slightly above the glass-transition temperature. The material and the freezing process have been characterized in detail by analyzing the frequency-doubling process of the fundamental radiation of a Nd: YAG laser in the liquid crystal. Under favourable conditions, we obtained second-order susceptibilities as large as χzzz = 0.5 pm/V.

Novel glass-forming ferroelectric liquid-crystal material of high second-order nonlinearity

Low-molar-mass liquid crystals consisting of a binary nematic mixture of twoβ-naphthylester which exhibit an anisotropic glassy state at room temperature have recently proven to be a suitable material for erasable optical data-storage applications. Using the holographic-grating technique, it is shown that more than 1000 all-optical write, read and erase cycles can be realized without remarkable loss of reversibility. The recording intensities are of the order of 100 W/cm2 and optical erasure can be achieved with about twice that intensity. The times for recording and erasure of the optical gratings range on the millisecond scale and the stored gratings persist several months with a diffraction efficiency of typically 1 %. The spatial resolution has been proven down to 2 µm so far. The obtained results are compared with other reversible recording materials.

H. Schmid

Papers

Observation of blue phases in chiral networks

Storage of erasable laser induced holographic gratings in low molar mass cholesteric liquid crystals

Storage of laser-induced holographic gratings in discotic liquid crystals

Novel glass-forming ferroelectric liquid-crystal material of high second-order nonlinearity

New glassy liquid crystals for optical data-storage applications