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...

Thermophotovoltaics (TPV) is the process by which photons radiated from a thermal emitter are converted into electrical power via a photovoltaic cell. Selective thermal emitters that can survive at temperatures at or above ∼1000°C have the potential to greatly improve the efficiency of TPV energy conversion by restricting the emission of photons with energies below the photovoltaic (PV) cell bandgap energy. In this work, we demonstrated TPV energy conversion using a high-temperature selective emitter, dielectric filter, and 0.6 eV In 0.68 Ga 0.32 As photovoltaic cell. We fabricated a passivated platinum and alumina frequency-selective surface by conventional stepper lithography. To our knowledge, this is the first demonstration of TPV energy conversion using a metamaterial emitter. The emitter was heated to >1000°C, and converted electrical power was measured. After accounting for geometry, we demonstrated a thermal-to-electrical power conversion efficiency of 24.1 0.9% at 1055°C. We separately modeled our system consisting of a selective emitter, dielectric filter, and PV cell and found agreement with our measured efficiency and power to within 1%. Our results indicate that high-efficiency TPV generators are possible and are candidates for remote power generation, combined heat and power, and heat-scavenging applications.

We demonstrate selective emission from a heterogeneous metasurface that can survive repeated temperature cycling at 1300 K. Simulations, fabrication, and characterization were performed for a cross-over-a-backplane metasurface consisting of platinum and alumina layers on a sapphire substrate. The structure was stabilized for high temperature operation by an encapsulating alumina layer. The geometry was optimized for integration into a thermophotovoltaic (TPV) system, and was designed to have its emissivity matched to the external quantum efficiency spectrum of 0.6 eV InGaAs TPV material. We present spectral measurements of the metasurface that result in a predicted 22% optical-to-electrical power conversion efficiency in a simplified model at 1300 K. Furthermore, this broadly adaptable selective emitter design can be easily integrated into full-scale TPV systems.

No abstract

We present an electrically tunable terahertz two dimensional plasmonic interferometer with an integrated detection element that down converts the terahertz fields to a DC signal. The integrated detector utilizes a resonant plasmonic homodyne mixing mechanism that measures the component of the plasma waves in-phase with an excitation field functioning as the local oscillator. Plasmonic interferometers with two independently tuned paths are studied. These devices demonstrate a means for developing a spectrometer-on-a-chip where the tuning of electrical length plays a role analogous to that of physical path length in macroscopic Fourier transform interferometers.2

No abstract

No abstract

We report, for the first time, the generation of non-degenerate photon pairs via spontaneous parametric down-conversion driven by Bound States in the Continuum resonances in semiconductor metasurfaces.