光彈調變橢圓術中的角度校正及其應用

Abstract

有別於歸零式技術，本論文利用三個光強度量測技術，量測系統之偏光片、光彈調變器及析光片等光學元件對樣品入射面的偏差角。先以穿透式設置調整得到元件相對之方位角後，偏光片角度設定於45度，藉由PPEMSA橢圓術架構及適當的入射角，並利用零階貝塞函數之零點特性量測析光片方位角於半週期內60度間隔之三個直流光強度，計算其偏角值，此外相同的量測也可求出橢圓參數ψ。透過光彈調變器之相位調變，配合鎖相放大器，量測一倍頻與二倍頻交流光強度比值，可得到另一橢圓參數Δ。此量測技術，不但可精確校正系統光學元件及入射面，亦可應用在材料橢圓參數的量測上。

Other than nulling method, we propose a three-intensity-measurement technique to determine the azimuth deviation of polarizer (P), photoeiastic modulator(PEM) and analyzer(A) to the surface of incidence. We first used a straight-through set-up to align the relative azimuthal positions of elements, then adjusted the azimuth of P at 45o. Arranging a PPEMSA ellipsometry at the required incident angle and the zero point of zero-order Bessel function, we can measured a set of dc intensity through three analyzers evenly spaced by 60°in half a cycle to find the azimuth deviation. The ellipsometric parameterψcan also be determined from the same measurements. Another parameterΔcan be obtained by measuring the ratio of 1f, 2f ac intensity. This technique is capable to align the optical elements to the reflection surface, and obtain the ellipsometric parameter of material.