突破繞射極限的次波長成像

Subwavelength imaging for overcoming the diffraction limit

游雲開(Yun-Kai You)

指導教授 ： 薛文証

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.10258

摘要

本文主要在討論由超穎材料所製成的左手透鏡與金屬透鏡的成像原理與特性。首先左手透鏡方面，我們探討左手透鏡之光學傳播函數及穿透係數，並藉由傅立葉光學來分析左手透鏡的成像特性，結果顯示左手透鏡的確可藉由放大消逝波來突破繞射極限，但解析度會受到吸收效應的限制而降低，且由分析結果發現在吸收效應存在時，左手透鏡的成像能力被將局限於近場區域。此外在金屬成像的部份，我們利用同樣的方法來探討金屬透鏡的成像特性，並將金屬成像系統分為對稱結構與非對稱結構分別來討論。由分析結果顯示金屬透鏡同樣具有放大消逝波的功用，但無論是對稱結構或是非對稱結構在金屬透鏡成像中皆會產生較多的雜訊而影響成像品質，儘管如此金屬透鏡在近場區域內仍可突破繞射極限而達到更佳的解析度。

關鍵字

超穎材料 ； 左手透鏡 ； 金屬透鏡 ； 光學傳播函數 ； 消逝波 ； 解析度 ； 繞射極限

並列摘要

In this thesis, imaging properties and principles of lens made by metamaterial and metal are investigated. First of all, for left-handed lens, we investigate optical transfer function and transmission coefficient of left-handed lens and we employ Fourier optics to analyze the imaging characteristics of left-handed lens. The results show that left-handed lens indeed could overcome the diffraction limit by the amplification of the evanescent waves, but resolution will be limited by absorption effect, and the analysis also show that if absorption exist, imaging ability of left-handed lens will be restricted in near field. For metal lens, we analyze the characteristics of imaging in the same way with left-handed lens, we separate the metal imaging system into to part : symmetric and asymmetric structure. The results show that also metal lens could amplify evanescent waves, but both the symmetric and asymmetric structure in metal imaging will produce more noise to reduce imaging quality. In spite of this metal lens still can overcome the diffraction limit to achieve better resolution in near field.

並列關鍵字

metamaterial ； left-handed lens ； metal lens ； optical transfer function ； evanescent waves ； resolution ； diffraction limit

參考文獻

[1]　V. G. Veselago, “The Electrodynamics of Substances with Simultaneously Negative Values of and ” Sov. Phys. Usp. 10, 509-514 （1968）.

[2]　J. B. Pendry, A. J. Holden, W. J. Swewart, I. Youngs, “Extremely Low Frequency Plasmons in Metallic Mesostructures” Phys. Rev. Lett. 76, 4773-4776 （1996）.

[3]　J. B. Pendry, A. J. Holden, D. J. Robbins and W. J. Swewart, “Magnetism from Conductors and Enhanced Nonlinear Phenomena” IEEE Trans. Microwave Theory Tech. 47, 2075-2084 （1999）.

[4]　R. A. Shelby, D. R. Smith and S. Schultz,” Experimental Verification of a Negative Index of Refraction, “Science. 292, 77-79 （2001）.

[5]　P. Markoš and C.M. Soukoulis, “Transmission studies of left-handed materials,” Phys. Rev. B 65, 033401 （2001）.