奈米光學表面電漿式新穎記錄方式利用三維時域有限差分法之研究

3D-FDTD simulation of novel nano optical surface plasmon resonance recording method

林鉦育(Chen-Yuh Lin)

指導教授 ： 蔡定平

國立臺灣大學/理學院/物理研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.10302

摘要

從1983年開始，PHILIPS與SONY兩家公司幾乎主宰了整個光學記錄的走向，但是隨著資訊量非線性的成長，使得最早的640MB CD、當前流行的4.7GB DVD、下一個世代的25GB(50GB) Blu-ray Disc三者的存儲容量不再符合需求。不過上述儲存方式所採用的記錄技術皆是在遠場光學的領域內，在遠場光學的繞射極限下，要持續提昇記錄密度的方法有三種；(1)縮小光源波長(2)提高透鏡的數值孔徑 （N.A.）(3)增加介質的折射率。在近場光學領域中，1998年10月，提出在記錄層上添加一層Sb，並在上面開一個小洞，以類似探針的作用讀出近場訊號，2000年更進一步的提出利用AgOx當作近場作用層，使得讀取訊號得以再一次匯聚導出。1998年本實驗室認為能使近場訊號導出的現象肇因於侷域性表面電漿，換句話說，這是一項運用近場光學的技術來增加記錄容量的方法。將上述的概念延伸，內文提出一個新式記錄方法─利用次波長孔洞破壞高穿透奈米結構，再利用奈米結構與光反應所產生的表面電漿具有的侷域性質，進而持續減小「有效記錄點大小」，提昇記錄密度，並且建立一套以奈米光學原理為主的光學記錄模型。
內文分為以下四個主題：
一、 利用時域有限差分法來模擬電磁與物質的交互作用與相關理論探討，且針對各類光源、介電係數模型、大型結構的平行化、及數值後處理的技術開發。
二、 利用多層薄膜的理論，計算在不同材料性質，不同幾何結構下所具有的光學特性：高穿透、高反射、高吸收。及各類材料選取的優劣分析，並討論新式方法的原理。
三、 利用模擬技術討論使用各種不同材料在記錄層與反射層時，新式記錄方式的特性、分析各類機制的影響、及設計出可增加特定近場光學訊號，並且使其能在遠場讀出的結構。
四、 找出最佳參數及追求最佳記錄的結構，並使用所探討的機制延續討論在奈米尺度下利用奈米結構對光的操控的可能性。

關鍵字

奈米光學 ； 表面電漿 ； 近場光學記錄 ； 三維時域有限差分法

並列摘要

From 1983, two companies, PHILIPS and SONY, dominated almost the entire optical record - CD-ROM. People have developed many kinds of recording tools such as 640 MB CD, 4.7 GB DVD and 25 GB (50GB) of the Blu-ray Disc. However, information is getting non-linear growth and storage is not enough anymore. The original technology is based on the far-field optical but all of them are restricted by Rayleigh diffraction limit.

In order to break optical diffraction limit restrictions, people improve recording density in three ways: (1) shorten wavelength of light, (2)increase numerical aperture of the lens (N.A.) , and(3) increase the refractive index of medium. Therefore, this paper presents a new recording method – Use subwavelength hole to damage highly transparent nano-structure. Then, the impact of localized surface plasmon is within half wavelength of incident light. The equivalent size of recording point is narrowed and the requested space for recording point is smaller than before. I try to establish optical recording model with nano-optical principle.

There are four topics in this thesis:
I. Simulate the interaction between materials and light by using finite difference time-domain method. Then, introduce various light sources, the methods of parallel computation, and the models of the permittivity.
II. Calculate the optical properties of different materials and different geometric structures including penetrating, reflectivity and absorption rates by using multi-layer film theory. Then, compare the strengths and weakness of various types of materials. Besides, I describe the principle behind the new recording method.
III. Use three different kinds of material, amorphous Ge2Sb2Te5—amorphous Ge2Sb2Te5, amorphous Ge2Sb2Te5—Ag and crystallized Ge2Sb2Te5—Ag, in recording layer and reflective layer of the new recording methods. Then, analysis the characteristics under the above settings, impact of various mechanism including Fabry-Prot effect, localized surface plasmon, and effect of the cavity. Finally, I try to increase the signal in near field and design a readable structure in far field.
IV. Find the best parameters for different kinds of recording structure and discuss the manipulation of light by using modifications of nano-structure.

並列關鍵字

nano-optical ； surface plasmon ； near-field optical recording ； 3D-FDTD

參考文獻

[1] G. Binnig, H. Rohrer, C. Geber, and E. Wweibel, ”Surface Studies by Scanning Tunneling Microscopy,” Physical Review Letters, 49, 57-61(1982).

[3] E.H. Synge, "A suggested method for extending the microscopic resolution into the ultramicroscopic region," Phil. Mag., 6, 356 (1928).

[4] E.H. Synge, "An application of piezoelectricity to microscopy," Phil. Mag., 13, 297 (1932).

[5] J.A. O'Keefe, "Resolving power of visible light," J. of the Opt. Soc. of America, 46, 359 (1956).

[6] E.A. Ash and G. Nichols, "Super-resolution aperture scanning microscope," Nature 237, 510 (1972).