共振波長線寬對週期梯度導模共振濾波器光譜儀解析度之研究

Abstract

光譜儀在各領域應用中扮演重要角色，利用光學色散原理，分析光譜特性，運用光譜儀判讀光譜資訊，及各種物質結構與成分。隨著生醫、光電、電子等技術的發展，使用光譜儀分析光譜的需求也更加廣泛，但傳統光譜儀因結構複雜、體積龐大，限制了應用範圍。 本研究利用波導模態共振(GMR)分光原理，以微光機電技術，研發奈米等級的週期梯度波導模態濾波器(作為分光元件)，結合感光耦合元件 (CCD)，形成波導模態濾波器光譜儀。探討不同線寬 (linewidth)的共振模態與元件分光解析度的關係，分析線寬對CCD感測像素所能檢測的最低分光極限的影響。 週期梯度導模共振濾波器分析，量測週期梯度波導模態濾波器在不同光模態的穿透光譜，研究結果顯示，TM mode較TE mode有較窄的光譜半高寬(FWHM)。隨後，藉由不同光源，包含單光儀、LED光源、線性變化濾波片(LVF)結合寬頻光源，及Hg校正光源，對本研發之波導模態濾波器光譜儀，進行不同共振模態(TE, TM mode)分析。研究結果顯示，使用上述不同光源，TM mode較TE mode皆有較高的光譜分辨率，顯示TM mode與市售光譜儀有更相近的量測結果。本研發之微型光譜儀，製造成本低，有優良的光譜解析度，有效縮小光譜儀體積，使量測更為簡便，相當具有市場競爭力。

In this thesis, a gradient grating period-guided mode resonance filter (GGP-GMRF) spectrometer was designed and fabricated. The GGP-GMRF spectrometer is composed of a guided-mode resonance (GMR) filter with gradient grating period and a linear photodetector. The impact of the resonant line width of GMR on the spectral resolution was investigated. The GGP-GMR filter is a one-dimensional periodic surface relief structure consisting of a plastic substrate, a UV-curable polymer with a surface relief pattern and a high-refractive-index TiO2 film. At normal incidence, a specific wavelength of light excites the resonance of GMR filter structure and be reflected. The resonant wavelegnths of GGP-GMRF for both TE- and TM- polarized illumination show linear relationship with the spatial locations. Furthermore, the full width half maximum of TM mode is narrower than TE mode. To compare the spectral resolving capability of the designed spectrometer from TE- (broad line width) and TM-polarized modes (narrow line width), different kinds of light sources were used as illumination source, including monochromatic light, red LED, a linear variable filter with broadband light source and HG-1 calibration source. The results indicate that by operating at TM mode (narrower resonant linewidth), more accurate and higher spectral resolution can be obtained.