2006 Fiscal Year Final Research Report Summary
Photonic Crystals based on 3-D Periodically Structured Liquid Crystal and their Functional Applications
| Project/Area Number |
17360141
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | Osaka University |
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Principal Investigator |
OZAKI Masanori Osaka University, Graduate School of Engineering, Professor, 大学院工学研究科, 教授 (50204186)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHINO Katsumi Osaka University, Center for Advanced Sciense and Innovation, Speciality Appointed Professor, 先端科学イノベーションセンター, 特任教授 (70029205)
FUJII Akihiko Osaka University, Graduate School of Engineering, Associate Professor, 大学院工学研究科, 助教授 (80304020)
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| Project Period (FY) |
2005 – 2006
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| Keywords | liquid crystal / photonic crystal / self organization / defect mode / two photon excitation / cholesteric liquid crystal / ferroelectric liquid crystal / confocal microscope |
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| Research Abstract |
Liquid crystals including chiral molecule have a self-organized helical structure with nano-scaled periodicity, which can be regarded as a one dimensional (1-D) photonic crystal. We proposed a laser action in dye-doped cholesteric liquid crystals (CLCs) with a band-edge effect for an input excitation of the doped laser dye. We achieved increasing a lasing efficiency and decreasing a lasing threshold upon the band-edge excitation. We also performed theoretical calculation of a density of state (DOS) in the CLC. The DOS increased drastically by the band-edge excitation.
On the other hand, the photon localization caused by the imperfection in periodic structure has been expected as potential applications such as low threshold lasers and micro waveguides, which can be observed as a defect mode in the transmission or emission spectra. We proposed a new type of defect mode in a chiral liquid crystal on the basis of the local deformation of the 1-D periodic helical structure and demonstrated t
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he possibility of the wavelength tuning in this system. Especially, upon introducing multiple defects at a certain periodicity into the helical structure, it was found that a localized band appears in PBG. In this mode, photon is localized at each defect in the helicoidal structure.
We also investigated the photon localization in the double periodic structure, in which the helical periodic structure was contained in the 1-D periodic multilayer structure and acts as a defect in the 1-D photonic crystal. In this system, besides defect mode peaks due to the 1-D photonic crystal having the defect, a very sharp defect mode peak with a high Q-value appears at the edge of the band gap of the helix defect in the transmission spectrum. The enhanced laser action has also been observed on the basis of the new defect mode.
Using a two-photon confocal microscope lithograpy technique, we have tried to fabricate nano-defect structure in the chiral helicoidal system and higher-order confinement structure based on the chiral liquid crystals. Tunable defect mode and laser actions on this nano-modulated chiral helix structurre have been demonstrated. Less
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