光彈調變式偏光儀對 DR19/PMMA中光致線性雙折射現象之研究

Abstract

DR19是一種具極性的類液晶單軸分子，此類化合物之光致雙折射反應是各方研究之重點。本論文利用光彈調變式橢圓偏光儀量測DR19/PMMA受光激發下之線性雙折射的動態變化。分析光強度中之倍頻訊號，可以量得樣品之線性雙折射值。 我們分別改變垂直激發光源之入射角度和偏振態，並在各入射角下量其雙折射值:若將激發光源之偏振態設為 TM, 此塊材之線性雙折射值與入射角呈現負相關之關係，相位差最大值為24.3度；若將激發光源之偏振態設為 TE ，則此塊材之線性雙折射值與入射角呈現正相關之關係，相位差最大值為33.1度。 我們也量測DR19/PMMA之折射率，發現此塊材在照光過程中折射率保持在1.495+-0.001。

DR19 is a kind of rod-like uniaxial molecule with non-zero electric dipole moment and its photo-induced birefringence effect has been extensively studied. The PEM Ellipsometer is used to monitor the dynamic change of DR19/PMMA under exposure. The linear birefringence (LB) can be measured simultaneously. The birefringence of sample was probed by various incident angles under a normally inducing beam with the p- and s-polarized, respectively. In the study, we found the induced LB decreases under p-polarized light but increases under s-polarized with respect to the incident angle of probe beam. The refractive index under exposure was also measured by the ellipsometry near its Brewster angle, which remain to be 1.495+-0.001 in the whole process.