Nano Lett. http://doi.org/j77 (2013)

Nanoscale optical cavities offer a powerful means of controlling light. They can even modify spontaneous emission itself, if the source within emits light at a wavelength near the cavity resonance. Arka Majumdar and co-workers have now shown how graphene provides a way of electrically tuning the properties of a photonic-crystal cavity, creating a platform for unifying photonics and electronics.

Majumdar et al. perforated a thin silicon membrane with a hexagonal array of holes 90 nm in radius. The cavity comprised three filled-in holes plus a modified hole at each end. The researchers placed a graphene sheet on top of the photonic crystal before attaching electrodes.

The application of just a few volts shifted the cavity resonance (near 1500 nm) by approximately 2 nm, and increased the reflectivity by a factor of 4. This level of control is a result of the electric-field induced changes in the dielectric function of the graphene. The authors hope the idea might lead to small-footprint, high-speed electro-optic modulators.