An electro-optical modulator using a graphene-based plasmonic slot is disclosed. The electro-optical modulator is comprised of a substrate layer, a dielectric spacer, a graphene layer, a first metal layer, and a second metal layer. The metal layers create a plasmonic slot that modulates between a light absorptive and light transparent state depending on the application of voltage across the modulator. Two or four graphene layers may be used to reduce power consumption and the size of the modulator.