Label-Free Optical Microscope Based on a Phase-Modulated Femtosecond Pump-Probe Approach with Subdiffraction Resolution
Label-Free Optical Microscope Based on a Phase-Modulated Femtosecond Pump-Probe Approach with Subdiffraction Resolution
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DOI：
10.1021/acsphotonics.9b01821
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发表时间：
2020-03-18
期刊：
影响因子：
7
通讯作者：
Diau, Eric Wei-Guang
中科院分区：
文献类型：
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作者：
Fathi, Amir;Chung, Chao-Yu;Diau, Eric Wei-Guang
远场光学显微镜（OM）是一种强大的非侵入性，非破坏性的工具，用于研究亚微米结构和生物体，几十年来一直用于研究空间域中光与物质之间的相互作用。我们在这里报告一个复杂的无标记OM方法与超空间分辨率可视化ZnO纳米粒子。在三个飞秒脉冲中，两个用作1000 nm的泵浦，另一个用作774 nm的探测。两个泵浦（一个高斯形状，另一个环形形状）以180度的相位差产生。当在不存在第二环形泵的情况下使用常规泵-探测方法时，由于衍射的限制，观察到ZnO纳米颗粒显示出445 nm的粒度。相比之下，当第二环形泵被异相施加时，所获得的OM图像显示出低至96 nm的ZnO纳米颗粒。我们首次证明了所报道的相位调制泵浦-探测方法具有超越其光学衍射极限的空间分辨率的能力，并且具有在纳米材料和生命科学中用于无标记成像应用的潜力。
A far-field optical microscope (OM) is a powerful noninvasive, nondestructive tool to study sub-micrometer structures and organisms, which has been used for decades to study the interactions between light and matter in the spatial domain. We report here a sophisticated label-free OM method with superspatial resolution to visualize ZnO nanoparticles. Of three femtosecond pulses, two served as pumps at 1000 nm and the other one served as a probe at 774 nm. The two pumps (one of Gaussian shape and the other of toroidal shape) were generated with a phase difference of 180 degrees. When the conventional pump-probe approach was used in the absence of a second toroidal pump, a ZnO nanoparticle was observed to show a particle size of 445 nm because of the limit of diffraction. In contrast, when the second toroidal pump was applied out of phase, the obtained OM image showed a ZnO nanoparticle down to 96 nm. We demonstrated for the first time that the reported phase-modulated pump-probe approach has an ability for spatial resolution beyond its optical diffraction limit and a potential for label-free imaging applications in nanomaterials and life sciences.