72 results found
Dawood A, Park S, Parker-Jervis R, et al., 2021, Effect of mesa geometry on low-terahertz frequency range plasmons in two-dimensional electron systems, Journal of Physics D: Applied Physics, ISSN: 0022-3727
We demonstrate engineering of the low-terahertz range plasmonic spectra of two-dimensional electron systems by modifying their geometry. Speciﬁcally, we have modelled, fabricated, and measured two devices for comparison. The ﬁrst device has a rectangular channel, while the second is trapezoidal, designed to support a richer plasmonic spectrum by causing variation in the device width along the direction of plasmon propagation. We show that while plasmon resonant frequencies and ﬁeld distributions in the rectangular device can largely be described by a simple one-dimensional analytical model, the ﬁeld distributions modelled in the trapezoidal device shows a more complex pattern with signiﬁcant variation along the length of the channel, so requiring a two-dimensional treatment. The results illustrate the potential of modifying the channel geometry to obtain diﬀerent spectra in experiments, with potential applications in the design of novel terahertz-range devices, such as plasmon-based sources and detectors.
Sydoruk O, Zonetti S, Siaber S, et al., 2021, Scattering-induced amplification of two-dimensional plasmons: electromagnetic modeling, Journal of Applied Physics, Vol: 129, Pages: 1-12, ISSN: 0021-8979
Using two rigorous electromagnetic approaches, we study plasmon scattering in two-dimensional systems and show that plasmon amplification is possible in the presence of dc currents. Two scenarios are considered: plasmon scattering from an interface between different two-dimensional channels and plasmon reflection from electric contacts of arbitrary thickness. In each case, the effect of a dc current of the plasmon reflection and transmission coefficients and the plasmon power are both quantified. A resonant system is studied where plasmon roundtrip gain may exceed unity, showing the possibility of plasmon generation.
Syms R, Sydoruk O, Wiltshire M, 2021, Magneto-inductive HF RFID system, International Journal of Radio Frequency Identification Technology and Applications, Vol: 5, Pages: 148-153, ISSN: 1745-3216
Efforts to increase read range in passive HF RFID systems are hampered by the poor range scaling law of inductive coupling. An alternative approach to enlarging capture volume—increasing the lateral extent of the antenna—is proposed, using a magneto-inductive (MI) travelling wave arrangement to allow larger antenna sizes. A theory of load modulation in MI systems is first presented, together with field simulations in the capture volume. A 2.3 metre-long MI antenna is then constructed, and an active tag emulator is used to demonstrate load modulation. RFID is then demonstrated, with the antenna in both reflection and transmission modes, using a custom reader constructed from laboratory equipment. A transverse read range of 0.5 m is obtained using commercial off-the-shelf RFID cards with 12 W RF power, with high uniformity along the length of the antenna.
Park S, Zonetti S, Parker-Jervis R, et al., 2021, Terahertz magnetoplasmon resonances in coupled cavities formed in a gated two-dimensional electron gas, Optics Express, Vol: 29, Pages: 12958-12966, ISSN: 1094-4087
We report on both experiments and theory of low-terahertz frequency range (up to 400 GHz) magnetoplasmons in a gated two-dimensional electron gas at low (<4K) temperatures. The evolution of magnetoplasmon resonances was observed as a function of magnetic field at frequencies up to ∼400 GHz. Full-wave 3D simulations of the system predicted the spatial distribution of plasmon modes in the 2D channel, along with their frequency response, allowing us to distinguish those resonances caused by bulk and edge magnetoplasmons in the experiments. Our methodology is anticipated to be applicable to the low temperature (<4K) on-chip terahertz measurements of a wide range of other low-dimensional mesoscopic systems.
Voronov A, Sydoruk O, Syms RRA, 2021, Power waves and scattering parameters in magneto-inductive systems, AIP Advances, Vol: 11
Difficulties arise in the definition of power flow in transmission-line systems with a complex propagation constant. These were resolved by Kurokawa using quantities known as “power waves,” which contain both voltage and current terms and correctly separate power flow into forward- and backward-traveling components. Similar difficulties must arise for electromagnetic metamaterials since any discrete, periodic structure leads to band-limited propagation, with a complex propagation constant both inside and outside the bands due to loss and cutoff, respectively. Here, discrete power waves are defined for magneto-inductive (MI) systems, metamaterials based on chains of magnetically coupled LC resonators. These waves are shown to satisfy the discrete power conservation equation for MI waves and are used to calculate scattering parameters for multi-port MI devices without the anomalous predictions of conventional methods. The results will allow correct evaluation of internal scattering parameters in MI systems.
Parker-Jervis RS, Park SJ, Zonetti S, et al., 2020, On-chip terahertz spectroscopy of magnetoplasmons in a two-dimensional electron gas, 45th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), Publisher: IEEE, ISSN: 2162-2027
Siaber S, Zonetti S, Sydoruk O, 2019, Junctions between two-dimensional plasmonic waveguides in the presence of retardation, Journal of Optics, Vol: 21, ISSN: 2040-8978
Plasmons in two-dimensional waveguides are traditionally analysed within the electrostatic approximation, which assumes that the plasmon phase velocity is much smaller than the velocity of light. However, novel effects have recently been demonstrated for plasmons whose velocity is comparable to the velocity of light. In this retardation regime, electrostatic models are inaccurate. For a junction between two plasmonic waveguides, we present an analytical and a numerical model both valid in the retardation regime and compare them to an electrostatic model. We quantify the reflected and transmitted powers and the radiation loss in several scenarios. We found that power is radiated from a junction at the expense of the power of the reflected plasmon, but retardation has little effect on the phases of the reflected and transmitted plasmons. The radiation loss is typically below several percent when the plasmon velocities are five or more times below the light velocity. However, radiation still persists for slower plasmon velocities for a junction between a two-dimensional waveguide and a perfectly conducting sheet. As a result, retardation is expected to degrade the quality factors of plasmonic resonators without affecting their eigenfrequencies.
Syms RRA, Sydoruk O, Bouchaala A, 2019, Improved optical imaging of high aspect ratio nanostructures using dark-field microscopy, Nanotechnology, Vol: 30, ISSN: 0957-4484
Improvements to white light optical imaging of widely spaced, high aspect ratio nanostructures are demonstrated using dark-field field microscopy. 1D models of bright- and dark-field imaging are developed from rigorous modal diffraction theory by assuming that features are periodic. A simple model is developed to explain dark field results and simulated line images obtained using the two modalities are compared for different dimensions and materials. Increased contrast between etched features and the substrate is demonstrated in dark field, due to its reduced sensitivity to scattering from flat areas. The results are verified using silicon nanostructures fabricated by sidewall transfer lithography, and feature separation with improved tolerance to apparent substrate brightness is demonstrated during image segmentation using the Otsu method.
Siaber S, Zonetti S, Cunningham J, et al., 2019, Terahertz plasmon resonances in two-dimensional electron systems: modeling approaches, Physical Review Applied, Vol: 11, ISSN: 2331-7019
Known approaches to modeling terahertz plasmons in two-dimensional electron sys-tems may differ significantly in their assumptions. There has, however, been littleeffort to analyze the differences between and application of different models to thesame sets of structures. This paper discusses, develops, and compares several differenttheoretical approaches—namely, an effective-medium approximation, a transmission-line model, modal analysis, and full-wave simulations. In particular, wepresent atransmission-line model that takes into account the dielectric/air surrounding of atwo-dimensional system. Using modal analysis, we also solve analytically the problemof plasmon reflection and transmission when plasmons are incident ona junction be-tween gated and an ungated two-dimensional waveguides. Comparing the predictionsmade by the models for several structures, we found good agreement between full-wave simulations and both analytical and numerical modal analysis. The results ofthe effective-medium approximation and the transmission-line modelalso agreed witheach other, but differed quantitatively from full-wave simulations and modal analysis.We attribute the differences to the phases of plasmon reflection and transmission co-efficients obtained using the different approaches. Our analytical expressions for theplasmon transmission and reflection coefficients represent a simple yet accurate way to model plasmons in two-dimensional systems comprising both gated and ungated sections.
Dawood A, Wu J, Wood C, et al., 2019, Full-wave modelling of terahertz frequency plasmons in two-dimensional electron systems, Journal of Physics D: Applied Physics, Vol: 52, Pages: 1-10, ISSN: 0022-3727
While models of terahertz frequency plasmons in two-dimensional electron systems are usually developed by reducing the number of spatial dimensions, fully three-dimensional models may be needed for the design and analysis of realistic structures. Using full-wave electromagnetic simulations, we have analysed the plasmons and magnetoplasmons observed in two recent experiments. Here, we demonstrate agreement between the theoretical and the experimental results, and discuss further device characteristics such as plasmon transmission, reflection, absorption, and field distributions. We then compare the three-dimensional full-wave simulations with a two-dimensional model. Finally, we discuss approaches for increasing signal transmission and reducing reflection, with direct relevance for improving future experiments.
Sydoruk O, Siaber S, Zonetti S, 2019, Radiation from junctions between two-dimensional plasmonic waveguides, 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), Publisher: IEEE, ISSN: 2162-2027
Syms RRA, Bouchaala A, Sydoruk O, et al., 2018, Optical imaging and image analysis for high aspect ratio NEMS, Journal of Micromechanics and Microengineering, Vol: 29, ISSN: 0960-1317
A strategy for optical microscopy of high-aspect-ratio (HAR) nanoelectromechanical systems (NEMS) that combine large feature spacing and large height with sub-wavelength width is presented. Line images are simulated using a 2D model of incoherent imaging based on modal diffraction theory. Beyond a sufficient depth, it is shown that sub-wavelength features appear as dark lines, while wider features are visible as their edges. The results suggest NEMS and MEMS may be separated from background in images by detection of valleys in brightness. Results are confirmed by imaging of Si NEMS containing 100 nm wide features in a bright-field microscope. Algorithms for separation of NEMS, MEMS and background in microscope images based on valley detection, thresholding and masking are demonstrated.
Fobelets K, Panteli C, Sydoruk O, et al., 2018, Ammonia sensing using arrays of silicon nanowires and graphene, Journal of Semiconductors, Vol: 39, ISSN: 1674-4926
Ammonia (NH3) is a toxic gas released in different industrial, agricultural and natural processes. It is also a biomarker for some diseases. These require NH3 sensors for health and safety reasons. To boost the sensitivity of solid-state sensors, the effective sensing area should be increased. Two methods are explored and compared using an evaporating pool of 0.5 mL NH4OH (28% NH3). In the first method an array of Si nanowires (Si NWA) is obtained via metal-assisted-electrochemical etching to increase the effective surface area. In the second method CVD graphene is suspended on top of the Si nanowires to act as a sensing layer. Both the effective surface area as well as the density of surface traps influences the amplitude of the response. The effective surface area of Si NWAs is 100 × larger than that of suspended graphene for the same top surface area, leading to a larger response in amplitude by a factor of ~7 notwithstanding a higher trap density in suspended graphene. The use of Si NWAs increases the response rate for both Si NWAs as well as the suspended graphene due to more effective NH3 diffusion processes.
Panteli C, Fobelets K, Sydoruk O, 2017, Graphene Suspended on Silicon Nanowire Arrays for Enhanced Gas Sensing, 231st ECS Meeting, ISSN: 2151-2043
Sydoruk O, Siaber S, Pouzada D, et al., 2016, Modeling terahertz plasmons in coupled semiconductor resonators, IRMMW-THz 2016, Publisher: IEEE, ISSN: 2162-2035
Plasmons in two-dimensional systems find applications in terahertz oscillators, detectors, filters, plasmonic crystals, etc. Numerous approaches to modeling plasmonic spectra exists, but little work has been done to compare results from theoretical calculations with each other, and so to understand their limitations. Using three different techniques (full-wave simulations, mode matching, and trasmission-line model), we analyse here a realistic structure comprising three coupled plasmonic resonators. While the results of all three models offer qualitatively similar results, revealing a rich spectrum of coupled modes, the values of the predicted resonant frequencies differ between the models. The best agreement is found between full-wave simulations and mode matching, both of which are based on rigorous solution of Maxwell's equations.
Panteli C, Liu D, Sydoruk O, et al., 2016, Through graphene etching of porous Si by electroless metal assisted chemical etching, MNE
Wu J, Sydoruk O, Mayorov AS, et al., 2016, Time-domain measurement of terahertz frequency magnetoplasmon resonances in a two-dimensional electron system by the direct injection of picosecond pulsed currents, Applied Physics Letters, Vol: 108, ISSN: 1077-3118
We have investigated terahertz (THz) frequency magnetoplasmon resonances in a two-dimensional electron system through the direct injection of picosecond duration current pulses. The evolution of the time-domain signals was measured as a function of magnetic field, and the results were found to be in agreement with calculations using a mode-matching approach for four modes observed in the frequency range above 0.1 THz. This introduces a generic technique suitable for sampling ultrafast carrier dynamics in low-dimensional semiconductor nanostructures at THz frequencies.
Sydoruk O, Wu JB, Mayorov A, et al., 2015, Terahertz plasmons in coupled two-dimensional semiconductor resonators, Physical Review B, Vol: 92, Pages: 1-6, ISSN: 1550-235X
Advances in theory are needed to match recent progress in measurements of coupled semiconductor resonators supporting terahertz plasmons. Here, we present a field-based model of plasmonic resonators that comprise gated and ungated two-dimensional electron systems. The model is compared to experimental measurements of a representative system, in which the interaction between the gated and ungated modes leads to a rich spectrum of hybridized resonances. A theoretical framework is thus established for the analysis and design of gated low-dimensional systems used as plasmonic resonators, underlining their potential application in the manipulation of terahertz frequency range signals.
Sydoruk O, Choonee K, Dyer GC, 2015, Transmission and reflection of terahertz plasmons in two-dimensional plasmonic devices, IEEE Transactions on Terahertz Science and Technology, Vol: 5, Pages: 486-496, ISSN: 2156-342X
Plasmons in two-dimensional semiconductor devices will be reflected by discontinuities, notably, junctions between gated and non-gated electron channels. The transmitted and reflected plasmons can form spatially- and frequency-varying signals, and their understanding is important for the design of terahertz detectors, oscillators, and plasmonic crystals. Using mode decomposition, we studied terahertz plasmons incident on a junction between a gated and a nongated channel. The plasmon reflection and transmission coefficients were found numerically and analytically and studied between 0.3 and 1 THz for a range of electron densities. At higher frequencies, we could describe the plasmons by a simplified model of channels in homogeneous dielectrics, for which the analytical approximations were accurate. At low frequencies, however, the full geometry and mode spectrum had to be taken into account. The results agreed with simulations by the finite-element method. Mode decomposition thus proved to be a powerful method for plasmonic devices, combining the rigor of complete solutions of Maxwell's equations with the convenience of analytical expressions.
Hadjicosti K, Sydoruk O, Maier SA, et al., 2015, Surface polaritons in magnetic metamaterials from perspective of effective-medium and circuit models, Journal of Applied Physics, Vol: 117, ISSN: 1089-7550
Surface waves are responsible for many phenomena occurring in metamaterials and have been studiedextensively. At the same time, the effects of inter-element coupling on surface electromagnetic waves(polaritons) remain poorly understood. Using two models, one relying on the effective-mediumapproximation and the other on equivalent circuits, we studied theoretically surface polaritonspropagating along an interface between air and a magnetic metamaterial. The metamaterial comprisedsplit rings that could be uncoupled or coupled to each other in the longitudinal or transverse directions(along or perpendicular to the propagation direction). A metamaterial without inter-element couplingsupported a single polariton. When a moderate longitudinal coupling was included, it changed thewave dispersion only quantitatively, and the results of the effective-medium and the circuit modelswere shown to agree at low wavenumbers. However, the presence of a transverse coupling changedthe polariton dispersion dramatically. The effective-medium model yielded two branches of polaritondispersion at low values of the transverse coupling. As the coupling increased, both polaritonsdisappeared. The validity of the effective-medium model was further tested by employing the circuitmodel. In this model, surface polaritons could exist in the presence of a transverse coupling only if theboundary layer of the metamaterial included additional impedances, which could become non-Foster.The results reveal that the inter-element coupling is a major mechanism affecting the properties of thepolaritons. They also highlight the limitations of using bulk effective-medium parameters for interfaceproblems in metamaterials.
Hadjicosti K, Maier SA, Sydoruk O, 2015, Line-defect magneto-inductive waveguides and waveguide components, 9th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics (METAMATERIALS), Publisher: IEEE, Pages: 94-96
Sydoruk O, 2014, Amplification and generation of terahertz plasmons in gated two-dimensional channels: Modal analysis, JOURNAL OF APPLIED PHYSICS, Vol: 115, ISSN: 0021-8979
Hadjicosti K, Sydoruk O, Maier SA, et al., 2014, Surface polaritons born by inter-element coupling in magnetic metamaterials, 8th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics (Metamaterials), Publisher: IEEE
Sydoruk O, 2013, Amplification of drifting semiconductor plasmons and effects of carrier collisions and diffusion, JOURNAL OF PHYSICS D-APPLIED PHYSICS, Vol: 46, ISSN: 0022-3727
Syms RRA, Sydoruk O, Solymar L, 2013, Noise in one-dimensional metamaterials supporting magnetoinductive lattice waves, PHYSICAL REVIEW B, Vol: 87, ISSN: 2469-9950
Sydoruk O, 2013, Drifting plasmons in open two-dimensional channels: modal analysis, JOURNAL OF PHYSICS D-APPLIED PHYSICS, Vol: 46, ISSN: 0022-3727
Sydoruk O, 2013, Is amplification of semiconductor plasmons possible despite carrier collisions and diffusion?, 38th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), Publisher: IEEE, ISSN: 2162-2027
Syms RRA, Sydoruk O, Solymar L, 2013, Transmission-Line Model of Noisy Electromagnetic Media, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, Vol: 61, Pages: 14-22, ISSN: 0018-9480
Sydoruk O, Syms RRA, Solymar L, 2012, Amplifying mirrors for terahertz plasmons, JOURNAL OF APPLIED PHYSICS, Vol: 112, ISSN: 0021-8979
Sydoruk O, Zhernovaya O, Tuchin V, et al., 2012, Refractive index of solutions of human hemoglobin from the near-infrared to the ultraviolet range: Kramers-Kronig analysis, JOURNAL OF BIOMEDICAL OPTICS, Vol: 17, ISSN: 1083-3668
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