體積全像光柵作為光譜儀分光元件之研究

Abstract

本文闡述如何利用穿透式體積全像術的方式記錄於材料中，製作光柵光譜儀的繞射光柵元件，是一篇體積全像光學元件應用的描述。這種製作分光光柵元件的設計與方法，目的為改進傳統以薄光柵作為色散元件的解析度與頻譜響應。依據體積全像適用的《耦合波理論》並經計算而發現，體積全像容易記錄成擁有比一般薄光柵較好的解析度。而薄全像無法記錄成組合光柵，體積全像之繞射特性可以讓我們利用多工方式，在同一介質內將其記錄成組合光柵。一般用於光譜儀的分光薄光柵，設計成以馬達驅動而旋轉。（光柵所需轉動之角度是由單晶片擷取光電流訊號，將訊號轉為驅動馬達之電壓回傳而決定。）若以體積全像記錄組合光柵，則固定一入射角，便可為一定頻譜範圍內的多色光源作色散，讀取時無須轉動光柵。我們將設定如何製作此種分光光柵，包括記錄時所選取的入射角度，以及材料所能涵蓋到的波長。

The thesis, about an application of the volume holographic optical elements (VHOE), describes how to apply the technique of the transmission volume hologram recording to fabricate the diffraction grating elements for a spectrometer. The purpose of the designment and the method to produce dispersive grating elements is in order to improve the resolution and the spectral response of the dispersive thin grating elements. According to “the coupled wave theory” suitable for volume holographic gratings and due to calculating, we find volume gratings easily possess higher resolution than ordinary thin gratings after recording. For the thin hologram, however, the multiple gratings can not to be recorded. Due to the diffraction features of the volume hologram, we can utilize the trick of multiplexing to record multiple gratings in a medium. Generally, the thin holographic grating used in the spectrometer was designed rotatably by the driving motor. If we record multiple gratings to the volume hologram, we can fix the incident angle to disperse any multicolor light source in some given spectral ranges without rotating the grating during reading out. We will set how to make this kind of gratings, including the angles of incidence we choose during recording, and what kinds of wavelength the medium can relate.