顯微光譜與共軛焦技術的應用發展

Abstract

本論文主要描述開發寬頻共焦顯微光譜儀及其相關應用，除了具備顯微影像放大之功能且能進行微米尺度之光譜分析，由於本研究之共焦顯微光譜儀具備高動態對比特性，因此適合做精準穿透或反射光譜影像之分析研究，並且本系統具備線性及旋光偏振量測能力。由於顯微系統光路具備寬頻復消色差之設計，因此結合共焦架構以及配合低反射率之校正片，能進一步獲得待測樣品之絕對反射率，並推得折射率之分佈及色散特性。 在微區光譜量測分析方面，本研究將共焦顯微光譜儀應用於掃描漸變折射率透鏡之反射強度，推得漸變折射率透鏡端面橫截面之材料色散分布以及多波長折射率分佈曲線。在顯微影像量測分析方面，直接用來量測各種光纖端面之反射強度影像，透過低反射率黑色玻璃作為絕對反射率之校正片，直接推得光纖端面多波長折射率分佈影像。這是首次使用顯微鏡搭配鹵素燈源直接用來量測待測樣品寬頻折射率之研究。 因應微奈米光學待測樣品具備寬頻偏振光譜特性，本研究設計一種獨特光學機構，只使用一組高精密旋轉馬達進行切換及旋轉等動作，達成寬頻波段切換全偏振產生與解析之功能，可進行待測樣品之線性二色性、圓二色性及線性雙折射等之特性研究。 本論文所提出的量測方法有光學操作簡單、寬頻量測、高量測解析度及精準度以及高重現性等優點。

We develop a confocal microspectrophotometer with a halogen lamp to directly scan the surface reflectivities on the end of the GRIN lens. The pure fused silica is used to be a reference standard for deducing the absolute reflectivities of the Ge-doped core. Then, multi-wavelength refractive index profiles of the Ge-doped core can be further determined based on the Fresnel equation. Moreover, this work shows a connection between the material dispersion of the GRIN rod and the Ge-doped concentrations measured by an energy dispersive spectrometer. A direct image method of surface reflectivities on a cleaved fiber end with a filtered halogen lamp and a TE-cooled CCD with high dynamic range is proposed to measure the multi-wavelength refractive index profiling (RIP). A polished black glass is used to be a reference standard for measuring the absolute reflectivity of the fiber end. With the developed calibration procedures, both the spatially dependent sensitivity and spectral responsivity of the CCD pixels can be eliminated to achieve the high spatial accuracy. Tested fiber is connected with a fiber terminator to prevent errors from the backside return light. With the present method, the RIP can be precisely measured for not only multi-mode fibers but also single-mode fibers. This study also proposes an innovative filter wheel for multi-channel polarization state switching. Two orthogonal linear polarization states or two orthogonal circular polarization states can be easily switched by this apparatus for the characteristic of linear dichroism and circular dichroism. The above methods have several merits such as easy operation, broadband measurement, high resolution, high accuracy and rapid measurement.