石英之相位及橢圓傾角的量測

Abstract

本實驗是延續使用我們實驗室的偏光儀系統來量測單片石英式四分之一波長補波片與楔形石英晶體的雙折射及旋光特性，主要目的就是為了與去年所作的複合石英式四分之一波長補波片的結果相互比較，以得知其間之相位延遲Δ與精圓傾角ε的差異。 本實驗分別以氦氖雷射與鹵素燈加濾波片為光源系統對石英式四分之一波長補波片（複合式及單片式）作量測。兩補波片在氦氖雷射所量測的相位延遲都很接近理想的 90 度，但是以鹵素燈為光源的量測結果，單片式主相位延遲只有74.37度，主要是其光源之頻寬太寬導致的結果；另外複合式之橢圓傾角皆幾乎是單片式的十倍左右。由於氦氖雷射的光點太大及鹵素燈之濾波片的頻寬又太寬而無法測得楔形石英晶體的相位延遲皆在同一個 2π之內。本實驗確定了此量測法的極限。

A polarimeter system is used to measure the birefringence and optical activity of a multi-order quartz quarter waveplate. The results were compared with that of first- order type. Two types of source, a He-Ne laser and a Tungsten Halogen, which was filtered through a narrow band filter, were used to examine the phase retardation and ellipse of quartz wave plates. The phase retardations of both waveplates measured by He-Ne laser are close to the ideal 90°, but that of multi-order type measured by Tungsten Halogen is only 74.37°. Since the bandwidth of filter is much wider than that of laser, the multi-order phase retardation can cause a large discrepancy. In addition, the ellipse of first-order is almost ten times that of multi-order type, this property is still in study. The similar technique was also used to measure a wedge type quartz crystal. Because the spot size of He-Ne laser is over 1mm, we were not able to resolve its phase retardation. In the system of tungsten light, the bandwidth of its filter is also too wide to resolve its phase retardation. The limitation of this polarimetric method is obtained in this experiment.