Vicentini Edoardo, Nuansing Wiwat, Niehues Iris, Amenabar Iban, Bittner Alexander M, Hillenbrand Rainer, Schnell Martin
Opt Express. 2023 Jul 3;31(14):22308-22322. doi: 10.1364/OE.492213.
We report the development and characterization of a detection technique for scattering-type scanning near-field optical microscopy (s-SNOM) that enables near-field amplitude and phase imaging at two or more wavelengths simultaneously. To this end, we introduce multispectral pseudoheterodyne (PSH) interferometry, where infrared lasers are combined to form a beam with a discrete spectrum of laser lines and a time-multiplexing scheme is employed to allow for the use of a single infrared detector. We first describe and validate the implementation of multispectral PSH into a commercial s-SNOM instrument. We then demonstrate its application for the real-time correction of the negative phase contrast (NPC), which provides reliable imaging of weak IR absorption at the nanoscale. We anticipate that multispectral PSH could improve data throughput, reduce effects of sample and interferometer drift, and help to establish multicolor s-SNOM imaging as a regular imaging modality, which could be particularly interesting as new infrared light sources become available.
我们报告了一种用于散射型扫描近场光学显微镜（s-SNOM）的检测技术的开发与特性，该技术能够同时在两个或更多波长下进行近场幅度和相位成像。为此，我们引入了多光谱伪外差（PSH）干涉测量法，即把红外激光组合起来形成一束具有离散激光线光谱的光束，并采用时间复用方案以允许使用单个红外探测器。我们首先描述并验证了将多光谱PSH应用于商用s-SNOM仪器的实现过程。然后，我们展示了其在负相位对比度（NPC）实时校正中的应用，这为纳米级弱红外吸收提供了可靠成像。我们预计，多光谱PSH可以提高数据通量，减少样品和干涉仪漂移的影响，并有助于将多色s-SNOM成像确立为一种常规成像方式，随着新的红外光源问世，这可能会特别引人关注。
