Khonina Svetlana N, Golub Ilya
Image Processing Systems Institute of the Russian Academy of Sciences, Samara 443001, Russia.
J Opt Soc Am A Opt Image Sci Vis. 2012 Oct 1;29(10):2242-6. doi: 10.1364/JOSAA.29.002242.
We compare different beam combinations for stimulated emission depletion microscopy. The four considered copolarized, mutually symmetric, but complementary write + erase beam combinations are circularly polarized beam + circularly polarized vortex with charge +1 or -1, azimuthally polarized with a vortex + azimuthally polarized, and radially polarized beam + radially polarized with a vortex. The resulting fluorescent spot was calculated for plane incident pump and erase beams, for plane waves with added high NA annular ring apertures, and when both incident beams were optimized with amplitude-phase masks. For all three incident wave cases, the azimuthal polarization combination consistently produces spots 15%-30% smaller than the commonly used, circularly polarized light combination (the first from above). The two other polarization combinations produce even smaller, of the order of nanometers/0.003λ, fluorescent spots with a caveat of having nonzero erase beam intensity in the center. Nevertheless, these combinations can be advantageous when exploiting PF, i.e., using molecules that respond solely to the longitudinal (or only to transversal) component of the illuminating field.
我们比较了受激发射损耗显微镜的不同光束组合。所考虑的四种共偏振、相互对称但互补的写入+擦除光束组合为圆偏振光束+电荷为+1或-1的圆偏振涡旋光束、方位角偏振涡旋光束+方位角偏振光束以及径向偏振光束+带涡旋的径向偏振光束。针对平面入射泵浦光束和擦除光束、添加了高数值孔径环形光圈的平面波以及使用振幅相位掩模对两束入射光束进行优化的情况，计算了产生的荧光光斑。对于所有三种入射波情况，方位角偏振组合产生的光斑始终比常用的圆偏振光组合（上述第一种）小15% - 30%。另外两种偏振组合产生的荧光光斑甚至更小，约为纳米级/0.003λ，但存在中心擦除光束强度非零的问题。然而，当利用偏振荧光（PF），即使用仅对照明场的纵向（或仅对横向）分量有响应的分子时，这些组合可能具有优势。
