Progress in surface wave optical microscopy research at University of Science and Technology of China

[ China Instrument Network Instrument Development ] Surface wave optical microscopy is mainly used to study the interaction of light and matter at the surface or interface, and the behavioral characteristics at the surface or interface of the sample. Currently used surface wave optical microscopy is Surface Plasmon Resonance Microscopy (SPRM) using surface plasmon waves (Surface Plasmons, SPs) supported by metal (usually gold or silver) as the illumination source. However, SPRM has two shortcomings, which limits its wider application. First, due to the propagation characteristics of SPs, the spatial resolution of SPRM in the SPs propagation direction is usually several micrometers, which is much larger than the diffraction limit of light waves. Second, because SPs require specific excitation conditions and the numerical aperture of the microscope objective is limited, SPRM has certain requirements on the wavelength, polarization and substrate material of the incident light. For example, the incident light must be long-wave and must be p-polarized. Light, the sample must be placed on a metal material.

In response to the above shortcomings, Zhang Douguo, professor of the Micro-nano Optics and Technology Group of the University of Science and Technology of China, Professor Wang Pei, and Professor Liu Xu and Yan Cuifang from Zhejiang University, Research Fellow, Anhui Institute of Optics and Fine Mechanics, Hefei Institute of Material Science, Chinese Academy of Sciences Liu Jianguo, Gui Huaqiao, Professor Zou Gang of the Department of Polymer Science and Engineering, China University of Science and Technology, and Professor of the University of Maryland School of Medicine, JR Lakowicz, proposed and implemented a new surface wave optical microscopy imaging technology based on rotating illumination. The resolution of the mark imaging has expanded the application of surface wave optical microscopy. The related research results are published in the international journal Science Advances with the title of Label-free surface-sensitive photonic microscopy with high spatial resolution using azimuthal rotation illumination. )on.

Figure 1a shows a rotating lighting module loaded on an autonomous optical microscope. The scanning galvanometer adjusts the incident angle of the beam accurately and at a high speed, and the azimuth angle is rotated at a high speed between 0° and 360° while maintaining the radial angle (the resonance excitation angle of the surface wave corresponding to θ) (Fig. 1b) ), and then propagate the SPs in all directions. Without the need for image processing, the time-averaged effect of images acquired with the detector naturally increases the SPRM imaging resolution. As shown in Fig. 2a, the imaged sample is a curved dielectric nanowire. Only a fuzzy pattern can be seen by conventional SPRM, and there are many artifacts caused by stripes. With the rotating illumination SPRM, the nanowire can be effectively distinguished. The shape and curvature (Fig. 2b). Contrastive experiments prove that rotating illumination effectively improves the resolution of SPRM imaging and solves the first shortcoming of SPRM.

In order to solve the second shortcoming, Bloch Surface Waves (BSWs) loaded with dielectric multilayer films were proposed to replace SPs of metal films, thus developing another surface wave optical microscope: Bloch surface Wave microscopy (BSWM). The advantage is that the dielectric film (the top material is glass) is better than the metal film and easy to biochemically modify; BSWM can work both on long waves and short waves; the penetration depth of BSWs can be adjusted to achieve different depths of surface Imaging; BSWM can work with p-polarized and s-polarized incident light, which is beneficial for the measurement and characterization of polarization-sensitive samples. Based on these advantages, BSWM has a wider range of applications.

The first author of the paper is the graduate student of the Department of Optics and Optical Engineering, Yan Yan, and the graduate student of the research group, Chen Junxue (now working at Southwest University of Science and Technology). The author of the communication is Zhang Douguo. The above research work was supported by the Ministry of Science and Technology, the National Natural Science Foundation of China, and the Science and Technology Department of Anhui Province. The related sample production process was supported by the instrument support and technical support of the Micro-Nano Research and Manufacturing Center of the University of Science and Technology of China.

(Original title: progress in surface wave optical microscopy research)