On‐Chip Plasmonic Vortex Interferometers

Abstract

Since the late 19 th century, enormous endeavors have been made in extending the scope and capability of optical interferometers. Recently, plasmonic vortices that strongly confine the orbital angular momentum to surface have attracted considerable attention. However, current research interests in this area have focused on the mechanisms and dynamics of polarization-dependent single plasmonic vortex generation and evolution, while the interference between different plasmonic vortices for practical applications has been unexplored. Here, a method for flexible on-chip spin-to-orbital angular momentum conversion is introduced, resulting in exotic interferograms. Based on this method, a new form of interferometers that is realized by the interference between customized plasmonic vortices is demonstrated. Within wavelength-scale dimension, the proposed plasmonic vortex interferometers exhibit superior performance to directly measure the polarization state, spin and orbital angular momentum of incident beams. The proposed interferometry is straightforward and robust, and can be expected to be applied to different scenarios, fueling fundamental advances and applications alike.

Meta-optics inspired surface plasmon devices

“…Reproduced with permission from Ref. [269], © 2022 Wiley. (u), (v) Phase distributions for LCP and RCP incidences, and microscopy image of fabricated sample (u); simulated and measured SP field distributions under different incidences (v).…”

“…In 2022, Lang et al generalized the design into a ring shape [see Fig. 9(q)] and adopted it to achieve independent launching of multiple SP vortices under LCP and RCP incidences [269] . Figure 9(r) illustrates the calculated (left panels) and measured (right panels) results, where SP fields resulting from the interference of plasmonic vortices of topological charges −3 and +2 can be obtained under LCP incidence, while SP fields resulting from the interference of plasmonic vortices of topological charges −1 and +2 can be obtained under RCP incidence.…”

“…Similar to the holographic design of SPs, this design strategy introduces simultaneous modulation of the amplitude and phase [267] . Based on it, Lang et al [269] proposed an on-chip plasmonic vortex interferometer, realizing independent interference of arbitrary plasmonic vortices generated from two spin channels. Subwavelength plasmonic structures have different phase modulation manners for SPs and transmitted free-space light, and phase manipulation of transmitted free-space light emerges in the exit channel that is cross-polarized with incident light.…”

“…(i), (j) Results of plasmonic vortex interferometers for measurements of the polarization state (i); spin and orbital angular momenta (j). Reproduced with permission from Ref [269],. © 2022 Wiley.…”

Tailoring spatiotemporal dynamics of plasmonic vortices

“…Nevertheless, there are still some puzzles or shortages in this field. For plasmonic vortex generation, despite the sole or combined use of propagation phase and geometric phase can all achieve plasmonic vortex of target topological charge 25,26 , the actual differences of their spatiotemporal dynamics have remained unexplored. For characterization methods, the PEEM suffers from nonlinear spin-orbit coupling between the probing circularly polarized pulse and the propagating plasmonic vortex 20,28 , which can hardly obtain the exact evolution dynamics.…”