Optically and electrically tunable Dirac points and Zitterbewegung in graphene-based photonic superlattices

We demonstrate that graphene-based photonic superlattices provide a versatile platform for electrical and all-optical control of photonic beams with deep-subwavelength accuracy. Specifically, by inserting graphene sheets into periodic metallodielectric structures, one can design optical superlattices that possess photonic Dirac points (DPs) at frequencies at which the spatial average of the permittivity of the superlattice (epsilon) over bar vanishes. Similar to the well-known zero-(n) over bar band gaps, we show that these zero-(epsilon) over bar DPs are highly robust against structural disorder. We also show that, by tuning the graphene permittivity via the optical Kerr effect or electrical doping, one can induce a spectral variation of the DP exceeding 30 nm, at mid-IR and THz frequencies. The implications of this wide tunability for the photonic Zitterbewegung effect in a vicinity of the DP are also explored.