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Polarization-insensitive optical modulators based on single ENZ-graphene layers

We show a strategy to design polarization-insensitive electro-optical modulators based on the use of single-layer graphene sheets working at the ε-near-zero (ENZ) regime. An external voltage is used to change the optical properties of graphene at will, allowing dynamical tuning of the permittivity between dielectric and metallic behavior. As a proof of concept, we designed an ultra-compact modulator, with a minimum length of 5.22 µm, to produce a 3 dB modulation depth when working at the center of the optical C-band (λ = 1550 nm). The modulation principle is based on the high electromagnetic absorption associated to the ENZ mode of graphene. Our approach can be used for highly integrated, cost-effective and energy-efficient nanophotonic circuits in future optical communication networks.