Induced transparency by coupling of Tamm and defect states in tunable terahertz plasmonic crystals

Photonic crystals and metamaterials have emerged as two classes of tailorable materials that enable the precise control of light. Plasmonic crystals, which can be thought of as photonic crystals fabricated from plasmonic materials, Bragg scatter incident electromagnetic waves from a repeated unit cell. However, plasmonic crystals, like metamaterials, are composed of subwavelength unit cells. Here, we study terahertz plasmonic crystals of several periods in a two-dimensional electron gas. This plasmonic medium is both extremely subwavelength (similar to gimel/100) and reconfigurable through the application of voltages to metal electrodes. Weakly localized crystal surface states known as Tamm states are observed. By introducing an independently controlled plasmonic defect that interacts with the Tamm states, we demonstrate a frequency-agile electromagnetically induced transparency phenomenon. The observed 50% in situ tuning of the plasmonic crystal band edges should be realizable in materials such as graphene to actively control plasmonic crystal dispersion in the infrared.