非均向光學薄膜之偏極轉換量測與應用

Measurement and Application of Polarization Conversion from an Anisotropic Thin Film

彭成瑜(Cheng-Yu Peng)

指導教授 ： 任貽均

國立臺北科技大學/機電學院/機電科技研究所/博士(2007年)

摘要

本論文利用稜鏡/非均向光學薄膜/空氣組態增強斜向入射的偏極轉換反射率，來探討單層柱狀結構薄膜隨角度和波長的光學特性與光學常數的量測。發現在特定的入射角範圍會反射偏極轉換的帶通光譜，並分析膜層厚度、入射角、入射平面角對光譜曲線的影響。實驗上以斜向沈積方法製鍍單層柱狀氟化鎂薄膜，當變化入射角時，會造成帶通光譜曲線的位移；而變化入射平面角(旋轉基板)會改變柱狀結構的方位，並造成光譜曲線的位移。另外，發現在單層非均向光學薄膜的架構下，只要再加鍍一層均向性薄膜(安排在稜鏡/非均向性薄膜/高折射率均向薄膜/空氣系統和稜鏡/非均向性薄膜/低折射率均向薄膜/空氣系統)便可產生窄帶偏極轉換光譜；而寬帶偏極轉換光譜可由系統(稜鏡/低折射率均向薄膜/非均向性薄膜/空氣)獲得。
另一方面，偏極轉換隨角度變化相當靈敏，可以用來測量非均向性薄膜的光學常數。因此本論文探討隨入射角度變化的偏極轉換反射率曲線，基於變化光學常數對角頻譜曲線的靈敏度分析，而光學常數的精確度可由入射角與強度量測的解析能力來決定。非均向性薄膜的光學常數包含三個主軸折射率、柱狀傾角、膜層厚度，在此提出三角形收斂方法將光學常數的精確度限制在量測誤差的範圍內，僅使用簡易而靈敏的強度量測方法即可精確測量非均向性薄膜之光學常數。

關鍵字

非均向光學薄膜 ； 偏極轉換 ； 光學常數

並列摘要

This work presents the polarization conversion reflectance (PCR) is enhanced by light reflected from a single-layered system (prism/anisotropic thin film/air) at a certain incident angle range. The columnar magnesium fluoride film was prepared by oblique angle deposition. The relations between wavelength and angular spectra of PCR and optical constants of the prism/anisotropic thin film/air configuration are built and discussed. The band-pass PCR wavelength spectrum can be modulated by changing thickness, orientation of deposition plane, and the angle of incidence. In addition, arranging an isotropic thin film yields the narrowband PCR spectrum with respect to the prism/anisotropic thin film/low-refractive thin film/air system and prism/anisotropic thin film/high-refractive thin film/air system. The broadband PCR spectrum is obtained by arranging prism/ low-refractive thin film/anisotropic thin film/ air system.
On the other hand, it is shown that the angular-dependent PCR is sensitive enough to determine optical constants. The sensitivities of the angular spectrum of PCR to variations of optical constants are calculated and analyzed. Based on the sensitivity calculation, the accuracy of detected optical constants can be derived by considering the resolution ability in angle and intensity measurement. The anisotropic optical constant determination, including three principal indices, a tilt angle, and a thickness, can be determined from the sensitive-angular spectrum of PCR. Here, the triangle convergence method proposes that the optical constants can be resolved to approach the restricted range from measurement inaccuracy.

並列關鍵字

anisotropic thin film ； polarization conversion ； optical constants

參考文獻

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