以二階光柵的一階繞射量測方法校正LC-R2500相位調變器之相位延遲之研究

Phase Correction in LC-R2500 Using the First-order Diffraction of Binary Phase Gratings

簡得育(Te Yu Chien)

指導教授 ： 徐巍峰

國立臺北科技大學/電資學院/光電工程系研究所/碩士(2009年)

https://doi.org/10.6841/NTUT.2009.00108

摘要

液晶空間光調變器(Liquid-crystal spatial light modulator, LC-SLM)是本實驗室用來實現繞射光學元件(Diffractive optical elements, DOEs)的主要元件之一，其原理為利用液晶加電壓後，會使光波發生相位延遲並產生相位差分佈函數。本研究檢測之液晶空間光調變器為Holoeye公司製造的LC-R2500，其為反射式、液晶扭轉角為45度。

在使用液晶空間光學調變器作為繞射元件前，我們需先對它進行振幅與相位光波調制特性的量測。本論文在振幅調變(反射率)量測方面，我們針對不同的偏振片角度和分析片角度，直接量取監控光與反射光光功率以計算其反射率特性曲線;相位量測方面是利用二階光柵在其繞射場量測一階繞射點的光強，藉由改變相鄰的灰階值差，量測其一階繞射點的光強變化，再經由加入反射率值的計算，可計算出實際的相位延遲量。由於不同偏振方向的光波入射至LC-R2500所產生的相位延遲和反射光強均有所不同，因此，針對不同應用的課題，我們對偏振角和液晶分子夾約正負10度以內的情況來做量測。

關鍵字

液晶空間光調變器 ； 繞射光學元件 ； 相位延遲

並列摘要

The liquid-crystal spatial light modulator (LC-SLM), LC-R2500 by Holoeye CO., will be used in replace of phase-only diffractive optical elements in our laboratory. It provides a corresponding phase delay to the incident light depending on the applied voltage. The twist angle of liquid crystal in LC-R2500 is and the light is operated in the reflective mode.

Before using LC-R2500 to implement the diffraction optical elements, we need to develop a fast and reliable method to calibrate the intensity and phase modulations of LC-R2500.To measure the intensity reflectance, we calculated the intensity reflectance of LC-R2500 at various angles of the polarizer and the analyzer by measuring the intensities of the reference beam and the reflective beam. The averaged intensity reflectance was about 0.7, and the reflectance decreases as the increase of the applied voltage; To obtain the phase modulation, we measured the intensity of the positive first diffraction order of a binary-phase grating. By changing the difference of the two gray levels, and applying the previously-obtained reflectance, we calculate the phase difference of the two grey levels. Because the polarizer angles of incident beam to LC-R2500 would affect the phase modulation and reflection modulation, we measured range of polarizer angles between +10 and -10 degree.

並列關鍵字

LC-SLM ； DOE ； Fraunhoffer diffraction

參考文獻

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