Spatiotemporal manipulation of high-order plasmonic vortex fields in a modified Archimedean spiral structure by a...

Plasmonic vortex (PV) field has garnered widespread attention due to the orbital angular momentum (OAM) it carries, which provides topological charge as another channel for information transmission, transportation, and encoding. Dynamical modulation of higher-order PV field will enable flexible responses to various application scenarios and optimize the light-matter interaction. Here, we propose to utilize the time-dependent frequency component in the chirped femtosecond laser pulse as a new degree of freedom for spatiotemporal modulation of the OAM of the PV field in a modified Archimedean spiral structure comprised of two wavelength-dependent PV lenses without the necessity to alter the polarization of the incident light. By employing a chirped femtosecond light pulse, ultrafast switching of the topological charge in PV field from 3 to -5 and from 5 to -3 of the excited PV field within the femtosecond timescale has been achieved. The switching time of the OAM of the PV field can be actively controlled by varying the pulse duration and chirp coefficient of the incident laser pulse. The results indicate that the switching time between the different topological charges in the PV field is directly proportional to the pulse duration and inversely proportional to the chirp coefficient of the chirped pulse light. Ultrafast modulation of the PV field has the potential application in various fields, including optical communication, quantum information, and topological optics, laying a foundation for the development of PV devices.