Nanoscopy and NIC@IIT , Istituto Italiano di Tecnologia , Via Morego 30 , 16163 Genoa , Italy.
Department of Physics , University of Genoa , Via Dodecaneso 33 , 16146 Genoa , Italy.
ACS Nano. 2019 Aug 27;13(8):9673-9681. doi: 10.1021/acsnano.9b05054. Epub 2019 Aug 5.
The application of ultrafast pulsed laser sources and spectroscopic techniques enables label-free, deep-tissue optical microscopy. However, circumvention of the diffraction limit in this field is still an open challenge. Among such approaches, pump-probe microscopy is of increasing interest thanks to its highly specific nonfluorescent-based contrast mechanisms for the imaging of material and life science samples. In this paper, a custom femtosecond-pulsed near-infrared pump-probe microscope, which exploits transient absorption and stimulated Raman scattering interactions, is presented. The conventional pump-probe configuration is combined with a spatially shaped saturation pump beam, which allows for the reduction of the effective focal volume exploiting transient absorption saturation. By optimizing the acquisition parameters, such as power and temporal overlap of the saturation beam, we can image single-layer graphene deposited on a glass surface at the nanoscale and with increased layer sensitivity. These results suggest that saturation pump-probe nanoscopy is a promising tool for label-free high-resolution imaging.
超快脉冲激光源和光谱技术的应用使得无标记、深层组织光学显微镜成为可能。然而，在这个领域中，规避衍射极限仍然是一个开放的挑战。在这些方法中，由于其基于瞬态吸收和受激拉曼散射相互作用的高特异性非荧光对比机制，泵浦探针显微镜越来越受到关注，可用于对材料和生命科学样本进行成像。在本文中，提出了一种利用瞬态吸收和受激拉曼散射相互作用的定制飞秒脉冲近红外泵浦探针显微镜。该显微镜将传统的泵浦探针配置与空间整形的饱和泵浦光束相结合，通过利用瞬态吸收饱和来减小有效焦体体积。通过优化采集参数，如饱和光束的功率和时间重叠，我们可以在纳米尺度上对沉积在玻璃表面上的单层石墨烯进行成像，并提高了层灵敏度。这些结果表明，饱和泵浦探针纳米显微镜是一种用于无标记高分辨率成像的有前途的工具。
