橢圓偏光儀在光感材料的應用

Abstract

本實驗室現有以下四種橢圓偏光術 (1) 簡式橢圓偏光儀，此種技術已成功的完成了影像式橢圓偏光儀； (2) 即時光彈調變式橢圓偏光儀， 利用數據截取卡中四個鎖相放大器的功能，我們可以以高於 10 組/秒的量測速度同時監視調變振幅及橢圓偏光參數的變化； (3) 事後分析式橢圓偏光儀，此種方法已達光彈調變器的量測極限，20 μs；(4) 閃頻式影像式橢圓偏光儀，此法業已克服了數位照像機資訊傳輸太慢的問題， 每13 秒一對的二維橢圓偏光參數已可取得。 我們將使用已建立的 ”即時光彈調變式橢圓偏光儀” 研究光折變材料在光照射下而成雙折射特性的機制。交通大學光電系的許根玉及電物系的林烜輝兩位教授均是從事全像材料研究的專家亦將是此研究的合作者; 我們最近曾對他們製成的PQ-PMMA 塊材，作過一些初步的研究，利用橢圓偏光儀在曝光下量測所得的折射率的變化要比使用繞射效率所推算的大， 但由兩個方法所量得的雙折射率差則相同，故本研究的主要問題是確認兩個方法所量的物性異同。我們對可逆性全像材料在偏極光的曝照下，其分子重新排列的方向有著濃厚的興趣，由於我們可以即時量出曝光下的光軸方向及相位，其折射橢球的變化將是本研究的主要研究內容。

There are four configurations of ellipsometry in our laboratory: (1) PSA simple imaging ellipsometry, 10 min/set with lateral and thickness resolution of 4 μm and 0.2 nm, respectively; (2) in situ/real time PEM ellipsometry, DAQ system and its four channels lock-in ability, we can monitor both the modulation amplitude of PEM and photoinduced birefringence process in the same time; (3) post flight analysis in PEM ellipsometry, which has already reached to the temporal limit of the system- 20 μs; (4) Stroboscopic illumination imaging ellipsometry, this technique has already conquer the slow data transfer in CCD system, now 13sec for one set of ψ and Δ imaging for imaging ellipsometry. It is our interest to extend this “in situ/real time monitoring technique” to investigate the photoinduced birefringence process. This work will be collaborated with Professor Ken Y. Hsu (Department of Photonics) and Shiuan Huei Lin (Department of Electrophysics) of NCTU, both of them are the expert for holography and also interested in fabricating the phenanthrenequinone-doped copolymers materials for holographic storage. The refractive index changes under exposure will be our main interest to measure by the PEM ellipsometry. In our preliminary study of PQ-PMMA under the exposure of 488 nm (blue), the refractive index changes measured by our ellipsometric technique is much higher than what was obtained in diffraction efficiency technique. The mechanism of photoinduced variation is one of our targets for this proposal. In addition to the data storage of holographic material, we are also interested in some reversible photorefractive materials (DR19/PMMA) for understanding the photoinduced birefringence mechanism of doped polymers.