Browsing by Author "Wu, Jin-Jei"

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Brightness Enhancement with a Fingerprint Chiral Nematic Liquid Crystal
(2011-03-01)
Lee, King-Lien
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Wu, Jin-Jei
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Chen, Tien-Jung
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Wu, Yeong-Shiun
;
Chen, Fu-Chen
We demonstrate a brightness enhancement element that can be laminated to a linear polarizer for increasing the optical efficiency of a liquid crystal display device. The device structure is a chiral nematic liquid crystal (CNLC) with a fingerprint texture. For an unpolarized incident light, our experimental results show that the combination of a CNLC film and a conventional linear polarizer can achieve a transmittance of over 50%. The CNLC film increases the optical efficiency of a conventional polarizer by 21.7%. The detailed mechanism of such a CNLC-polarizer system is analyzed. (C) 2011 The Japan Society of Applied Physics
Computer simulation of the similar-Helfrich deformation during the transient planar to planar transition in cholesteric liquid crystals
(2004)
Yao, I-An
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Chen, Shu-Hsia
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Wu, Jin-Jei
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光電工程學系
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Department of Photonics
The three-dimensional dynamic relaxation process in cholesteric liquid crystals with low thickness to pitch ratio ((sic)2) after switching off an electric field have been numerically investigated both for cells with parallel boundaries and for ones with perpendicular boundaries. For cholesteric liquid crystal cells with different surface alignment conditions, our simulation results show that the mechanism of transition from homeotropic to planar state is entirely different. In a cell with parallel boundary conditions, the transition from homeotropic to planar is in a sequence of homeotropic - transient planar-planar. In a cell with perpendicular boundary conditions, the relaxation from homeotropic to planar is in a different sequence of homeotropic - planar. The similar-Helfrich deformation only occurs during the transient planar - planar transition. Based on our simulation results, we can also show that the relaxation from homeotropic to planar in a cell with perpendicular boundary conditions is faster than that in a cell with parallel boundary conditions.
Investigation of random lasing characteristics from dye-doped twisted nematic liquid crystals in wedge cell
(2016)
Lin, Sheng Hung
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Chen, Po-Yen
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Wu, Jin-Jei
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Chen, Yao-Hui
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Tsay, Shwu-Yun
The output polarization and slope efficiency of random laser could be controlled by the rubbing direction of PI and temperature, respectively, from dye-doped twisted nematic liquid crystals within wedge cell.
Variation in the Absolute Photonic Band Gap of Rods Ranging from Square to Octagonal in Square Lattices
(2011-07-01)
Hu, Chung-An
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Chang, Kuo-Pin
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Yang, Su-Lin
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Shen, Lin Fang
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Wu, Jin-Jei
The band structures and field patterns of dielectric rods in square lattices are calculated using the plane-wave method. The rods with various cross-sectional shapes from square to octagonal at a fixed filling-factor are constructed to assess the geometry effect of photonic crystals to their band gap properties. Analytical results indicate that the corner profiles of rods significantly affect the E- and H-polarization bands in resonance frequency and field distribution. The absolute photonic band gap is closed in the square lattice when square dielectric rods are replaced with octagonal dielectric rods. (C) 2011 The Japan Society of Applied Physics