Browsing by Author "Cheng, YK"

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Far-infrared resonance in split ping resonators
(2004-02-01)
Hsu, AC
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Cheng, YK
;
Chen, KH
;
Chern, JL
;
Wu, SC
We experimentally investigated the resonance effect of planar metallic split ring resonators (SRRs) in the far-infrared region (FIR) (similar to10.6 mum). Experimental results indicated that they exhibit resonance around 10.6 mum, implying negative permeability in the FIR region. Furthermore, the ratio of effective dimensions of the SRR cell and the wavelength of the incident beam was around I which suggested a wide scale independence. This size tolerance is useful in realizing the meta-materials with negative indices of refraction in the optical wavelength domain.
Irradiance formations in hollow straight light pipes with square and circular shapes
(2006-02-01)
Cheng, YK
;
Chern, JL
;
光電工程學系
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Department of Photonics
We investigated, both analytically and numerically, the irradiance formation of an asymmetrically located Lambertian light source in hollow straight light pipes with square and circular shapes. The uniform irradiance distribution in a square light pipe and hot-spot localization in a circular light pipe were examined and determined semianalytically. Typical factors of influence, such as light-pipe length, width, and source size, were identified with extensive simulation. Mien the ratio of light-pipe length and width was less than 0.5, the deviation from uniformity could be more than 20%. But once the source size was large enough (approximately half of the incident port), such that the Lambertian characteristics of the source dominated the irradiance distribution, the uniformity deviation was reduced. Furthermore, a quantity of root-mean-square circular differences was defined in order to identify the shape deformation of the light pipe; it was found that the peak value of the hot spot decreased exponentially with the deformation scale. The influence of nonperfect reflectivity of the pipe wall on irradiance formation was also examined for a square light pipe; when the reflectivity is larger than 90%, the difference in uniformity is less than 10% and uniform irradiance remains, provided that the ratio of light-pipe length and width is larger than 1; even the source is located asymmetrically. (c) 2006 Optical Society of America.