| 1. |
- Lagerwall, Sven, 1934, et al.
(författare)
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Liquid Crystals: Cholesteric, Guest-Host, and Polymer-Dispersed
- 2015
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Ingår i: Encyclopedia of Optical and Photonic Engineering Second Edition. - 9781351247177 ; , s. 1443-1450
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- If we abandon the mirror symmetry present in the ordinary nematics, a new world opens up for applications, for photonics as well as for displays. The basic new phenomenon that now appears is scattering. In practice, we enter this domain by using cholesterics, which is the chiral form of nematics. The nematogenic molecules might themselves be chiral, but we could also, in principle, obtain the cholesteric by adding chiral dopants to the material. If we add dichroic dyes or polymerizable materials to the liquid crystal, we can create highly interesting devices based on either absorption or scattering or both. Cholesteric and nematic devices based on scattering and dichroic effects will be discussed in this entry.
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| 2. |
- Lagerwall, Sven, 1934, et al.
(författare)
-
Liquid Crystals: Non-Linear Optical Effects
- 2015
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Ingår i: Encyclopedia of Optical and Photonic Engineering Second EditionP. - 9781351247177 ; , s. 1465-1472
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Today, inorganic crystals are the completely dominating materials for nonlinear optics (NLO) applications. The interest in organic materials for NLO has been constantly growing due to several factors. First of all, the polarization response to an externally applied field is of molecular electronic origin and, therefore, practically lossless and extremely rapid. Ultrafast, nonresonant nonlinearities in combination with relatively low value of dielectric permittivity can be found in organic single crystals, but these are expensive to grow. Polymer materials are cheap, but normally have very low polar order. Here, liquid crystals and liquid crystalline polymers have a particular interest due to their inherent order. While nematics show some peculiar effects which can be described as macroscopic, the polar smectics have a nonlinear response on the microscopic, electronic level which is fairly similar to what is found in crystals. We first briefly introduce the basic concepts and then discuss macroscopic and electronic effects in turn.
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| 3. |
- Lagerwall, Sven, 1934, et al.
(författare)
-
Liquid Crystals: Optical Properties and Basic Devices
- 2015
-
Ingår i: Encyclopedia of Optical and Photonic Engineering Second Edition. - 9781351247177 ; , s. 1473-1489
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Liquid crystals (LCs) are liquid or liquid-like states that are anisotropic. Therefore, they have less symmetry than ordinary liquids, but higher symmetry than crystals. The anisotropy makes them optically birefringent like most crystals. This entry relates the structural properties of the organic molecules that are the building blocks to the optical and the electro-optic properties of the different LC phases. The exceptional elastic properties of LCs are also described.
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| 4. |
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| 5. |
- Alkeskjold, T., et al.
(författare)
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Optically tunable bandgap fiber
- 2005
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Ingår i: Optics Photonics News, special edition "Optics in 2005". ; 16:12, s. 36-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 6. |
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| 7. |
- Alkeskjold, T. T., et al.
(författare)
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Highly tunable large-core single-mode liquid-crystal photonic bandgap fiber
- 2006
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Ingår i: Applied Optics. - 1539-4522. ; 45:10, s. 2261-2264
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a highly tunable photonic bandgap fiber, which has a large-core diameter of 25 μm and an effective mode area of 440 μm 2. The tunability is achieved by infiltrating the air holes of a photonic crystal fiber with an optimized liquid-crystal mixture having a large temperature gradient of the refractive indices at room temperature. A bandgap tuning sensitivity of 27 nm/°C is achieved at room temperature. The insertion loss is estimated to be less than 0.5 dB and caused mainly by coupling loss between the index-guided mode and the bandgap-guided mode.
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| 8. |
- Bjarklev, A., et al.
(författare)
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Liquid crystal photonic crystal fiber
- 2004
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Ingår i: Optics InfoBase Conference Papers. ; FiO-2004
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Konferensbidrag (refereegranskat)abstract
- A new class of hybrid photonic crystal fibers infiltrated with liquid crystals offers novel functionalities and ultimately takes full advantage of the different waveguiding effects demonstrated today. Among the most interesting possibilities, we demonstrate 'distributed' tunable filter and switching functionalities operating by the photonic bandgap effect.
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| 10. |
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