The propagation dynamics of surface plasmon polariton (SPP) in the Graphene waveguide arrays have analogy with the electron dynamics in atomic, molecular or condensed-matter systems. The quantum-classical analogies can be investigated by using surface plasmon polariton propagation in graphene sheet arrays.

The ultrafast optics group led by Prof. Peixiang Lu investigates the plasmonic Zener tunneling (ZT) in arrays of weakly coupled graphene sheet waveguides. By alternatively arranging the graphene waveguides with two different chemical potentials, the single SPP band splits into two minibands, and tunneling between them occurs at the edge of the Brillouin zone. With a linear gradient of the propagation constant introduced by appropriately tuning the chemical potential distribution over the graphene sheet, the SPPs exhibit a sequence of Bloch oscillations and ZT transitions in the arrays. The simulated tunneling rate coincides with the theoretical analysis based on the coupled-mode theory, which can be tuned by varying the chemical potential difference between adjacent graphene. The plasmonic ZT may find potential applications in graphene-based tunable beam splitters and interferometers on deep-subwavelength scale.    

This work is published on Opt. Lett. Vol. 41, No. 13, 2978 (2016). This work was supported by the National Natural Science Foundation of China under Grants No. 11304108.

Fig. (a) SPP beam undergoes pure Bloch oscillation. (b) SPP beam splits into two different paths in due to Zener tunneling. (c) Initially excited SPP band remains the most occupied one.