State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering , Nanjing University , Nanjing 210093 , China.
Anal Chem. 2018 Aug 7;90(15):9650-9656. doi: 10.1021/acs.analchem.8b02800. Epub 2018 Jul 17.
Objective-based surface plasmon resonance microscopy (SPRM) is a novel optical imaging technique that can map the spatial distribution of a local refractive index based on propagating surface plasmon polaritons (SPPs). Different from some other optical microscopy that shows a dot-like point spread function (PSF), a nanosized object appears as a wave-like pattern containing parabolic tails in SPRM. The geometrical complexity of the wave-like pattern hampered the quantitative interpretation of the PSF of SPRM. Previous studies have shown that two adjacent rings were obtained in the frequency domain by applying a two-dimensional Fourier transform to such patterns. In the present work, a ring-fitting method was developed to extract geometrical features out of the dual rings and to connect these features with several experimental parameters. It was found that the radius of ring equaled to the wavevector of SPPs. Its orientation revealed the propagation direction of SPPs. The coordinate distance of the center of ring gave the parallel component of the wavevector of the incident light, which was regulated by the incident angle. The ring-broadening factor reflected the propagation length of SPPs in a reciprocal relationship. Systematical and quantitative interpretations in the frequency domain not only advanced the basic understanding on the PSF of SPRM but also opened up the possibility to utilize these frequency-domain features for detection and sensing purposes in future.
基于目标的表面等离子体共振显微镜（SPRM）是一种新型的光学成像技术，可根据传播的表面等离激元（SPP）来绘制局部折射率的空间分布。与某些其他显示点状点扩散函数（PSF）的光学显微镜不同，纳米物体在 SPRM 中显示为包含抛物线尾巴的波状图案。波状图案的几何复杂性阻碍了 SPRM 的 PSF 的定量解释。先前的研究表明，通过对这些图案进行二维傅立叶变换，可以在频域中获得两个相邻的环。在本工作中，开发了一种环形拟合方法，从双环中提取几何特征，并将这些特征与几个实验参数联系起来。结果表明，环的半径等于 SPP 的波矢。其取向揭示了 SPP 的传播方向。环的中心坐标距离给出了入射光的波矢的平行分量，该分量由入射角调节。环展宽因子以倒数关系反映了 SPP 的传播长度。在频域中的系统和定量解释不仅提高了对 SPRM 的 PSF 的基本理解，而且为将来在检测和传感方面利用这些频域特征开辟了可能性。
