Electric field depolarization in high aperture focusing with emphasis on annular apertures
Electric field depolarization in high aperture focusing with emphasis on annular apertures
复制标题
DOI：
10.1046/j.1365-2818.2000.00739.x
复制
发表时间：
2000-10-01
期刊：
影响因子：
--
通讯作者：
Hell, SW
中科院分区：
文献类型：
--
作者：
Bahlmann, K;Hell, SW
光的电磁聚焦理论预测，在高孔径处会出现垂直于初始偏振的偏振场分量。尽管矢量去极化在聚焦理论中受到了相当多的关注，但还没有证据表明其在实验中的相关性。我们通过利用单分子荧光聚二乙炔层（其过渡偶极子沿单一方向取向）来测量焦点区域中垂直取向场的强度。对于用线性 x 偏振光照射的 1.4 数值孔径油物镜，我们发现 y 偏振焦场模数平方的积分相当于其 x 偏振对应物的 1.5%。特别是，我们在这里表明，当使用环形孔径时，去偏振会增加。由直径为入瞳直径 89% 的中心障碍物形成的环将积分提高到 5.5%。这与电磁聚焦理论预测的5.8%的值吻合较好；然而，去偏振也是由于折射聚焦的缺陷造成的。除了荧光显微镜和单分子光谱之外，焦平面中去偏振分量的测量强度还与强聚焦与偏振分析相结合的所有形式的光谱相关。
Electromagnetic focusing theory of light predicts that at high apertures field components arise that are polarized perpendicular to the initial polarization. Although vectorial depolarization has received considerable attention in focusing theory, no evidence has been presented as to its relevance in experiments. We measure the intensity of the perpendicularly orientated field in the focal region by utilizing monomolecular, fluorescent polydiacetylene layers whose transition dipoles are orientated in a single direction. For a 1.4 numerical aperture oil objective lens illuminated with linearly x-polarized light, we find that the integral of the modulus squared of the y-polarized focal field amounts to 1.5% of its x-polarized counterpart. In particular, we show here that the depolarization increases when using annular apertures. Annuli formed by a central obstruction with a diameter of 89% of that of the entrance pupil raise the integral to 5.5%. This compares well with the value of 5.8% predicted by electromagnetic focusing theory; however, the depolarization is also due to imperfections connected with focusing by refraction. Besides fluorescence microscopy and single molecule spectroscopy, the measured intensity of the depolarized component in the focal plane is relevant to all forms of light spectroscopy combining strong focusing with polarization analysis.