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

Abstract

Photonic crystals and metamaterials have emerged as two classes of tailorable materials that enable 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 (≈ λ/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 the plasmonic crystal dispersion in the infrared.Photonic band gaps 1 , strong light-matter interaction 2 , slow light 3 , and negative refractive index 4 arise in photonic crystal 5,6 structures due to Bragg scattering of electromagnetic waves from a repeated unit cell. However, the electromagnetic properties of photonic crystals engineered from bulk semiconductors, metals, and dielectrics generally are weakly tunable, if at all. Material systems such two dimensional electron gases (2DEGs) embedded in semiconductors 7,8 and graphene 9-11 offer a substantially more flexible electromagnetic medium. These plasmonic materials can both be lithographically patterned and electronically tuned, giving rise to a variety of subwavelength plasmonic devices that may be broadly controlled via an applied DC electric field. When a periodic structure is engineered from these systems, plasmonic band structure can be realized 12-15 . The 2DEG and graphene thus provide a platform for the exploration of widely tunable plasmonic band gap structures.Subwavelength plasmonic media that utilize a 2DEG formed at a GaAs/AlGaAs interface are the central focus of this article. Similar to the ω − q plasmon dispersion in graphene, the 2DEG plasmon dispersion depends explicitly upon both the plasmon wavevector and the AC conductivity of the medium. An effective methodology to describe plasma excitations in a 2DEG is that of an 'LC' plasmonic resonator 16 . Here L is the field effect tunable kinetic inductance of the 2DEG. The 2DEG capacitance can be introduced aswhere ef f is the effective permittivity of the embedded 2DEG and q is the plasmon wavevector 14,[17][18][19] . In high mobility 2DEG materials at microwave and THz frequencies, underdamped 'LC' plasma resonances are supported, allowing for propagation lengths on the order of tens of micrometers or plasmon wavelengths. The introduction of spatial periodicity to a 2DEG produces a plasmonic crystal (PC) where the 2DEG is a coherent plasmonic medium. Though a PC is physically more s...

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Phononic Crystal Made of Multilayered Ridges on a Substrate for Rayleigh Waves Manipulation

“…Moreover, for the two cases where either the resonance mode T 1 falls into the dip band A or mode T 2 falls into the band B, we had a situation very close to an acoustic analogue of electromagnetically-induced transparency (EIT) [60,61]. In fact, in plasmonic crystals for instance, the coupling between localized surface states (known as Tamm states) and the defect plasmonic state give an EIT-like behavior [62]. …”

Two Types of Localized States in a Photonic Crystal Bounded by an Epsilon near Zero Nanocomposite

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