Browsing by Author "Hwang, Shug-June"

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Cholesteric liquid crystal devices with nanoparticle aggregation
(2010-10-11)
Jeng, Shie-Chang
;
Hwang, Shug-June
;
Hung, Yu-Hsiang
;
Chen, Sheng-Chieh
;
影像與生醫光電研究所
A broadband cholesteric liquid crystal (CLC) device with a multi-domain structure is demonstrated by using an aggregation of polyhedral oligomeric silsesquioxane (POSS) nanoparticles in the CLC layer. The aggregation pattern of the self-assembled POSS nanoparticles depends on the concentration of POSS doped in the mixture of POSS/CLC and the cooling rate of the mixture from a temperature higher than the clear point. POSS-induced changes in the bulk and surface properties of the cholesteric cells, such as a promotion of homeotropic alignment, help to form a cholesteric structure with a broadband reflection of light; the latter can be used for improvement of bistable CLC devices. A higher POSS concentration and a higher cooling rate both improve the appearance of the black-white CLC device. (C) 2010 Optical Society of America
Cholesteric liquid crystal devices with nanoparticle aggregation
(2010-10-11)
Jeng, Shie-Chang
;
Hwang, Shug-June
;
Hung, Yu-Hsiang
;
Chen, Sheng-Chieh
;
影像與生醫光電研究所
A broadband cholesteric liquid crystal (CLC) device with a multi-domain structure is demonstrated by using an aggregation of polyhedral oligomeric silsesquioxane (POSS) nanoparticles in the CLC layer. The aggregation pattern of the self-assembled POSS nanoparticles depends on the concentration of POSS doped in the mixture of POSS/CLC and the cooling rate of the mixture from a temperature higher than the clear point. POSS-induced changes in the bulk and surface properties of the cholesteric cells, such as a promotion of homeotropic alignment, help to form a cholesteric structure with a broadband reflection of light; the latter can be used for improvement of bistable CLC devices. A higher POSS concentration and a higher cooling rate both improve the appearance of the black-white CLC device. (C) 2010 Optical Society of America
Electrically switchable liquid crystal Fresnel lens using UV-modified alignment film
(2010-12-06)
Jeng, Shie-Chang
;
Hwang, Shug-June
;
Horng, Jing-Shyang
;
Lin, Kuo-Ren
;
影像與生醫光電研究所
A simple method to make a switchable liquid crystal (LC) Fresnel lens with high diffraction efficiency and a low driving voltage was proposed based on the photo-induced surface modification of the vertical alignment layer. UV illumination alters the pretilt angle of alignment layers, a Fresnel zone-distribution hybrid alignment in the homeotropic LC cell can be straightforwardly achieved through UV exposure, yielding a concentric structure of the Fresnel phase LC lens. A remarkable diffraction efficiency of similar to 31.4%, close to the measured diffraction efficiency of the used Fresnel-zone-plate mask of 32%, was detected using a linearly polarized incident beam. (C)2010 Optical Society of America
Multi-wavelength laser tuning based on cholesteric liquid crystals with nanoparticles
(2016-04-27)
Chen, Sheng-Chieh
;
Lin, Jia-De
;
Lee, Chia-Rong
;
Hwang, Shug-June
;
影像與生醫光電研究所
A controllable multi-wavelength laser from a dye-doped cholesteric liquid crystal (DDCLC) cell is demonstrated by incorporating self-assembled polyhedral oligomeric silsesquioxane (POSS) nanoparticles (NPs). Multi-wavelength lasing emission is achieved by formation of multiple planar domains; this formation is dominantly influenced by the vertical alignment of NP clusters adsorbed on the substrate surface through a rapid thermal annealing process. The multi-wavelength lasing peaks are generated through the resultant effect of multiple longitudinal resonant modes of a Fabry-Perot etalon between the cell substrates and the amplification of fluorescence photons with the resonant wavelengths within the broadening long-wavelength edge of the reflection band of the multi-domain CLC. The amount of multi-wavelength lasing peaks can be controlled by changing the POSS NP concentration and the cooling rate of the cell. Furthermore, thermo-reversible control of the multi-wavelength lasing emission can be attained by controlling the thermally induced phase separation process of the POSS/DDCLC cell via a heating/cooling cyclic process.
Nanoparticle-doped polyimide for controlling the pretilt angle of liquid crystals devices
(2010-08-02)
Hwang, Shug-June
;
Jeng, Shie-Chang
;
Hsieh, I-Ming
;
影像與生醫光電研究所
;
Institute of Imaging and Biomedical Photonics
The pretilt angles of liquid crystal molecules can be controlled by using conventional polyimide (PI) alignment material doped with different concentrations of Polyhedral Oligomeric Silsequioxanes (POSS) nanoparticles, which have been observed to spontaneously induce vertical alignment. The addition of POSS in the homogenous PI changes the surface energy of the alignment layer and generates a variable pretilt angle. Experimental results demonstrate that the pretilt angle. p is a function of the POSS concentration, and can be tuned continuously over the range of 0 degrees
Nanoparticle-mediated Polyimide for Pretilt Angle Control of Liquid Crystals Devices
(2010)
Jeng, Shie-Chang
;
Hwang, Shug-June
;
Shieh, Yi-Ming
;
Chen, Sheng-Chieh
;
影像與生醫光電研究所
The pretilt angles theta(p) of liquid crystal molecules can be controlled by using conventional polyimide alignment (PI) material doped with different concentrations of Polyhedral Oligomeric Silsequioxanes (POSS) nanoparticle. The addition of POSS in the homogenous PI changes the surface energy of the PI and generates the variable Op. Experimental results demonstrate that Op is a function of the POSS concentration, and it can be controlled over the range of 0 degrees < theta(p) < 90 degrees.