Belsley Michael, Soares-de-Oliveira Joana, Pereira António J
Opt Express. 2024 Oct 21;32(22):39769-39784. doi: 10.1364/OE.532358.
Microscopes generally achieve better 2D imaging compared to 3D, and super-resolution microscopes often aggravate such axial-lateral resolution mismatch. A prime example is vortex phase-based stimulated emission depletion (STED) fluorescence microscopy, which only narrows the point-spread function laterally, thereby increasing the point-spread function (PSF) anisotropy. In this study, we developed a semi-analytical theory based on the Nijboer-Zernike expansion, developed a set of metrics and performed experiments to establish the merits of the alternative, bivortex phase-based, coherent-hybrid STED. We find that this mode reduces the axial-lateral resolution mismatch by providing access to PSF geometries that are strictly forbidden to the two conventional single-beam modes, emulating noisier multi-beam approaches. Both theory and experiment indicate that bivortex STED not only addresses the axial-lateral resolution gap but also delivers a higher signal-to-background ratio than the two more common STED modes that it bridges.
与三维成像相比，显微镜通常能实现更好的二维成像，而超分辨率显微镜往往会加剧这种轴向-横向分辨率不匹配的情况。一个典型的例子是基于涡旋相位的受激辐射损耗（STED）荧光显微镜，它只会在横向缩小点扩散函数，从而增加了点扩散函数（PSF）的各向异性。在本研究中，我们基于尼伯尔-泽尼克展开式开发了一种半解析理论，制定了一套指标，并进行了实验，以确定基于双涡旋相位的相干混合STED这种替代方法的优点。我们发现，这种模式通过提供传统单光束模式严格禁止的PSF几何形状，减少了轴向-横向分辨率不匹配，类似于噪声更大的多光束方法。理论和实验均表明，双涡旋STED不仅解决了轴向-横向分辨率差距问题，而且比它所衔接的另外两种更常见的STED模式具有更高的信噪比。
