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We propose a novel way to actively control the propagation of THz Surface Plasmon Polariton (SPPs) in plasmonic waveguides structured on semiconductors. The SPP characteristics (field confinement and mode propagation length) can be precisely tuned by optically pumping charge carriers to the conduction band of the semiconductor. This approach can be used to generate active and integrated THz components...
We theoretically discovered and experimentally manifested that the carrier population inversion in graphene results in stimulating emission of plasmons with a giant gain, leading to superradiant terahertz lasing from a structured graphene.
We experimentally study THz evanescent wave coupling in an array of parallel-plate waveguides in close proximity. We observe stronger coupling with larger plate separations and longer propagation paths.
We present an efficient photoconductive terahertz emitter based on a logarithmic spiral antenna array that incorporates plasmonic contact electrodes on a LT-GaAs substrate. Under a 400 mW optical pump power, the emitter generates 1.9 mW of terahertz radiation in the 0.1 – 2 THz range.
A theoretical model is developed that takes into account the detrimental effects of carrier collisions and diffusion on the amplification of drifting plasmons reflecting from conducting boundaries. It is found that, despite collisions and diffusion, amplification is possible for realistic parameters.
We propose InAlAs/InGaAs/InP high electron mobility transistors with an asymmetric chirped dual-grating-gate structure which greatly enhances plasmon instabilities. The fabricated device demonstrates an intense stimulated emission of terahertz monochromatic radiation at cryogenic temperatures for the first time.
We present a terahertz quantum cascade laser providing 875 mW two-facet output power in pulsed mode, at a frequency around 4.7 THz and at a heatsink temperature of 10 K. The laser has a single plasmon waveguide. The active region is based on four quantum wells with longitudinal optical phonon extraction.
An array of metallic posts sandwiched between two parallel metal plates supports highly-confined surface waves that can be regarded as spoof surface plasmons. This structure which is called the parallel-plate ladder waveguide (PPLWG) can be used for implementing THz guided-wave devices. In this paper, the effect of post shapes on waveguiding characteristics of PPLWG is analyzed and realization of...
The electromagnetic field around Planar Goubau transmission Line (PGL) offers the possibility of tailoring the response of metamaterials components such as single or multi-micro resonators type. In this paper, we suggest a novel design of filter based on PGL coupled with micro split rings resonators (SRR). The frequency selectivity of resonant-type metamaterial transmission lines suggests their application...
We investigate the photo-excitation of localized surface plasmon polaritons (LSPPs) in semiconductor structures at THz frequencies by the optical pumping of electrons across the semiconductor energy bandgap. This excitation can be actuated in picosecond time scales, enabling ultrafast THz plasmonics. The concept of active plasmonics can be extended to a full spatial and temporal optical control of...
Propagation of terahertz surface plasmon polaritons along plane metal-dielectric interfaces and their jumps across air gaps have been studied using monochromatic radiation of Novosibirsk free electron laser.
We are developing an all-semiconductor plasmonic platform for mid-infrared sensing which includes growth of epitaxial n-doped germanium films, spectroscopic test and electromagnetic design of plasmonic antennas.
Optimal focusing of surface plasmon polaritons in the center of a metal disc illuminated by radially polarized terahertz pulses is demonstrated. Due to the cylinder symmetrical structure surface plasmons can be excited along the entire circumference, which interfere constructively in the center of the disk forming a sharp frequency-depended focal spot. We map the field distribution on the disk by...
A high-speed room temperature THz imaging system is developed. The sensor consists of an array (64×64) of plasmonic semiconductor detectors. The detectors have broadband responsivity of up to 20 V/W in the frequency range 10 GHz – 1 THz. Pixel-to-pixel deviation of the sensor parameters is not larger than 20%. The sensor with an amplification electrical circuit provide shot times of 100 ms. The sensor...
We study the scattering, absorption and extinction of THz radiation by 2D plasmonic crystals formed by periodic arrays of semiconductor particles. The particles sustain localized surface plasmon resonances that can couple to diffracted orders of the array giving rise to hybrid plasmonic-photonic modes. These modes exhibit extraordinary extinction and narrow line widths. The coupling strength and,...
We demonstrate nanoscale IR imaging and spectroscopy by recording the elastically scattered light from an AFM tip. Applications such as chemical mapping of polymers, free-carrier semiconductor profiling and real-space mapping of plasmons in metal nanostructures and graphene will be discussed.
We report on an order-of-magnitude enhancement of sensitivity of CMOS-transistor-based THz detectors. At 2.54 THz, 3.13 THz and 4.25 THz, responsivity values of 336 V/W, 308 V/W, and 230 V/W and optimum noise-equivalent-power values of 63 pW/√Hz, 85 pW/√Hz, and 110 pW/√Hz are obtained.
We predict strong amplification of terahertz radiation by the stimulated generation of plasmons in a planar array of graphene micro/nanocavities. Amplification drastically enhances due to lateral and vertical confinement of the plasmons in graphene micro/nanocavities and superradiant nature of electromagnetic radiation from the array.
We first report evidence by using terahertz (THz) spectroscopy of plasmonic excitations in a topological insulator (TI) that was engineered in thin micro-ribbon arrays. Plasmons are due to Dirac quasi-particles of the two-dimensional electron gas which forms at the surface of TIs.
We present a design of plasmonic photoconductive detectors, which mitigates the low detection sensitivity limitation of conventional photoconductive terahertz detectors. By incorporating plasmonic contact electrode gratings in the photoconductive detector, average carrier transport path length to the contact electrodes is reduced, enhancing photoconductor responsivity significantly. As a proof of...
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