Browsing by Author "Yan, Wei"

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Interaction Between Negative and Positive Index Medium Waveguides
(2008-11-01)
Yan, Wei
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Shen, Linfang
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Yuan, Yu
;
Yang, Tzong Jer
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電子物理學系
The coupling between negative and positive index medium waveguides is investigated theoretically in this paper. A coupled mode theory is developed for such a waveguide system and its validity is verified. Interesting phenomena in the coupled waveguides are demonstrated, which occur in the case when the negative index medium waveguide in isolation guides its mode backward. A new type of coupled mode solution that varies exponentially with the coupling length is found in the special case when the propagation constants of two individual waveguides are nearly the same. A coupler operating in this case is insensitive to the coupling length, and its coupling efficiency can reach 100% as long as the coupling length is long enough. However, when the propagation constants of the two individual waveguides differ greatly, the coupled mode solution is still a periodic function of the coupling length, but the coupled power is output backward. In addition, the modes in the composite waveguide system are also studied using the coupled mode theory, and their fundamental properties are revealed.
Research on a Camera-Based Microscopic Imaging System to Inspect the Surface Luminance of the Micro-LED Array
(2018-01-01)
Zheng, Lili
;
Guo, Ziquan
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Yan, Wei
;
Lin, Yue
;
Lu, Yijun
A majority of luminance measurement systems are currently focused on measuring the total luminance of light-emitting diodes (LEDs). It has largely limit its application on micro-LEDs, which require capturing the microscopic surface luminance. In order to study the microscopic characteristics of micro-LED displays, in this paper we propose a practical method that can accurately measure the luminance of a whole micro-LED array and even the surface luminance distribution of any single micro-led chip on the array. The essentials of this method are a high-precision complementary metal oxide semiconductor camera and a self-made data processing algorithm. Results show that the maximum error of the luminance measurement is less than 8%, which can prove the accuracy of the method. The metrical wavelength range and the accuracy of system can be dynamically set according to the camera and microscope. Endowed with ultrahigh dynamic ranges, this system proves its competency for evaluating the spatially resolved distribution of luminance for high brightness micro-LEDs.