Reconfigurable plasmonic vortices on a flat metal film via symmetry control

We demonstrate the generation of reconfigurable plasmonic vortices on a flat and smooth metal film via dynamic symmetry control both theoretically and experimentally. This method eliminates the need for complex nanostructuring, offering a fabrication-free and dynamically tunable platform for integrated plasmonic devices. Based on the Richards-Wolf vectorial diffraction theory, explicit expressions for the field vectors and energy flux of three-dimensional surface electromagnetic waves are derived. Numerical results confirm that plasmonic vortices originate from the coupling and conversion of the incident optical vortex into a surface-bound plasmonic mode, with a π/2 rotation of the surface field relative to the symmetry-broken excitation. Near-field scanning optical microscopy measurements of the vortex intensity distribution show good agreement with theoretical predictions and simulations. Our work provides a comprehensive analytical and experimental framework for the all-optical dynamic control of plasmonic vortex fields.