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44 results on '"Liu, Cheng-Kai"'

21. Polarization-independent holographic gratings based on azo-dye-doped polymer-dispersed liquid-crystal films

Author

Fuh, Andy Ying-Guey, Chen, Che-Chang, Cheng, Ko-Ting, Liu, Cheng-Kai, and Chen, Wei-Ko

Subjects
Semiconductor films -- Optical properties, Semiconductor films -- Chemical properties, Semiconductor films -- Production processes, Semiconductor films -- Composition, Polarization (Light) -- Research, Diffraction gratings -- Properties, Diffraction gratings -- Production processes, Semiconductor doping -- Research, Polymers -- Optical properties, Astronomy, Physics
Abstract

We demonstrate polarization-independent holographic gratings (PIHGs) based on azo-dye-doped polymer-dispersed liquid crystal films. The PIHGs are recorded by irradiation under an intensity-modulated interference field, generated by two linearly polarized green optical beams, and by simultaneously applying a suitable AC voltage to the sample. The photoexcited azo dyes are adsorbed onto the UV-cured polymer film with their long axes parallel to the normal of the substrate. When the applied voltage is switched off, the PIHGs are generated with periodic modulation of liquid-crystal structures with transparently homeotropic and randomly scattered alignments. Additionally, the generated PIHGs can be completely switched off by an applied voltage. OCIS codes: 050.1950, 160.3710, 160.5470.

Published
2010

35. Expanding color gamut of reflective liquid crystal displays from filtering undesirable wavelengths of a light source by an embedded etalon

Author

Liu, Cheng-Kai, Yang, Tsung-Hsun, and Cheng, Ko-Ting

Abstract

This work demonstrates a method to reduce the intensity of the undesirable wavelengths of blue (B-) and green (G-) ambient lights to expand the color gamut of reflective liquid crystal displays (LCDs) by an embedded etalon. The built-in reflector of the reflective LCDs is replaced by the blue-green overlapping wavelengths filtering etalon, which is used to reduce the intensity of undesirable B- and G-primaries, thereby decreasing the color cross talk of B- and G-color filters. After etalon adoption, the color gamut can be expanded from 105.96% to 121.81% of National Television System Committee (NTSC) in International Commission on Illumination (CIE) 1976 color space. Compared with the color gamut of the display without the blue-green overlapping wavelength etalon, the maximum expansion of color gamut is ∼15.85%. Moreover, the balance between light loss and color gamut expansion should be taken into consideration.

Published
2017

44. Optical simulation of single-cell-gap transflective liquid crystal displays based on surface anchoring energy of periodical nano-grooved structures.

Author

Liu CK, Fuh AY, and Cheng KT

Abstract

The single-cell-gap transflective liquid crystal display (TR-LCD) based on periodic distribution of surface anchoring energy (SAE) of periodical nano-grooved structures is reported in this study. Different SAEs of planar-aligned nematic LC cells are associated with the threshold and operation voltages of the adopted LCs. Thus, according to the transmittance versus applied voltage curves, the regions with strong and weak SAEs in LC cells can be the transmission and reflection regions of a TR-LCD, respectively. According to the simulation results using 1D-DIMOS software, the phase retardation of a strong SAE region is approximately twice as large as that of a weak SAE region when a specific voltage is applied, and a suitable difference in SAE exists between these two regions. Moreover, various SAEs based on periodical nano-grooved structures can be fabricated to demonstrate the TR-LCD.

Published
2016
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