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Browsing by Author "Zeng, Hui-Kai"

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    A lighting mechanism for flat electron emission lamp
    (2009-03-02)
    Li, Jung-Yu
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    Chen, Shih-Pu
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    Li, Chia-Hung
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    Lin, Yi-Ping
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    Chou, Yen-I
    We propose a lighting mechanism for generating uniform planar light. The device integrates electron beams induced by gas discharge with cathodoluminescence at the anode, where the spectra of the emitted light depend entirely on the phosphor materials coated on the anode. Consequently, ultraviolet is not required and the usage of mercury can be avoided. In addition, the features of double-side lighting, transparency, and gray-scale images indicate that the flat electron emission lamp might become potential candidate for the next generation green lighting source.
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    Discharge and photo-luminance properties of a parallel plates electron emission lighting device
    (2011-01-03)
    Li, Chia-Hung
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    Liu, Ming-Chung
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    Chiang, Chang-Lin
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    Li, Jung-Yu
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    Chen, Shih-Pu
    The gas discharge and photo-luminance properties of a planar lighting source featuring highly uniform light emission and mercury-free design were studied. The current density-voltage characteristics and the associated gas discharge of the devices operating with the values of the ratio of electric field to gas pressure (E/p) between 4.3 kV/Torr-cm and 35.7 kV/Torr-cm indicate that the width of the cathode fall extends over the entire gap between the two electrodes and the device is mostly in the obstructed discharge regime. The optical emission analysis confirmed the electron collision-induced gas emissions and strong effect of gas pressure on the phosphor emission when operated at constant current density, both are indicative of the primary roles played by the electron energy. (C)2011 Optical Society of America
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    Enhanced stop-band rejection by symmetric feeding in 1.8 GHz cross-coupled planar HTS microwave filters
    (2007)
    Zeng, Hui-Kai
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    Wu, Kaung-Hsiung
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    Uen, Tseng-Ming
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    Gou, Yi-Shun
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    Juang, Jenh-Yih
    The superior performance manifested in characteristics of low pass-band insertion loss, high stop-band rejection, and sharp band edge skirt, has led the superconducting microwave filters one of the most attractive candidates for wireless communication applications. In this paper, we report the design and fabrication of the 4-poles cross-coupled planar microwave filters fabricated using YBCO superconducting thin films deposited on both sides of a LAO single crystal substrate by pulsed laser deposition. The resonator geometry allows one to miniaturize the 1.8 GHz filters onto a substrate with dimensions of 1 cm x 1 cm. We also demonstrate that by properly choosing the feeding configuration, filters with better selectivity, in particular with an additional pair of deep transmission zeros (poles) outside both sides of pass-band, can be achieved.
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    Secondary electron emission characteristics of oxide electrodes in flat electron emission lamp
    (2016-01-01)
    Chiang, Chang-Lin
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    Zeng, Hui-Kai
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    Li, Chia-Hung
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    Li, Jung-Yu
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    Chen, Shih-Pu
    The present study concerns with the secondary electron emission coefficient,., of the cathode materials used in the newly developed flat electron emission lamp (FEEL) devices, which essentially integrates the concept of using cathode for fluorescent lamp and anode for cathode ray tube (CRT) to obtain uniform planar lighting. Three different cathode materials, namely fluorine-doped tin oxide (FTO), aluminum oxide coated FTO (Al2O3/FTO) and magnesium oxide coated FTO (MgO/FTO) were prepared to investigate how the variations of. and working gases influence the performance of FEEL devices, especially in lowering the breakdown voltage and pressure of the working gases. The results indicate that the MgO/FTO bilayer cathode exhibited a relatively larger effective secondary electron emission coefficient, resulting in significant reduction of breakdown voltage to about 3kV and allowing the device to be operated at the lower pressure to generate the higher lighting efficiency. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
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    Significant color space blue-shift of green OLED emitter with sustaining lifetime and substantial efficiency enhancement
    (2017-08-28)
    Li, Jung-Yu
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    Chen, Shih-Pu
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    Siao, Huei-Jhen
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    Wu, Jin-Han
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    Chen, Guan-Yu
    In this study, we demonstrate that by embedding a plasmonic coupling metal layer beneath the active layer of an organic light-emitting diode, the resultant device is capable of inducing significant blue shifts in CIE color space coordinates of emitting light from the green emitting material without compromising the lifetime of the parent material. The implemented device consists of multilayers of organic emitting materials sandwiched by two thin metal layers to form a metal-dielectric-metal (MDM) cavity-like structure. The original green emission with CIE coordinates of (0.22, 0.56) was significantly color space blue-shifted to CIE coordinates of (0.10, 0.53). The MDM device exhibits an efficiency of 62 cd/A at a luminance of 1000 cd/m(2), which represents a two-fold enhancement of current efficiency. Moreover, the spectral peak intensity is 4.3 times higher than that in a conventional device, which is much higher than that expected for an optical microcavity model, suggesting that the Purcell effect resulting from the coupling of surface plasmon waves may contribute to the extra enhancement of emission intensity. Published by AIP Publishing.
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