Plasmonic Focusing of a High-Order Cylindrical Vector Beam for On-Chip Detection

We investigate the interaction between cylindrical vector beams (CVBs) and metallic annular structures. The mechanisms for plasmonic focusing and field distributions are studied both analytically and numerically. We demonstrate that the focusing patterns are locked with the order of CVBs due to the polarization selectivity for the excitation of plasmonic fields, which can be employed as a simplified yet efficient means of characterizing and detecting CVBs. The robustness of the focusing pattern is analyzed as a deviation between the centers of the CVBs and nanoring is introduced, providing a quantitative indicator of the relationship between the maximum deviation value and the focusing patterns. Our research contributes to a deeper understanding of interactions between CVBs and nanostructures, paving the way for novel applications in light detection and optical imaging.