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.
Techniques to precisely characterise RF components at milli-Kelvin temperatures support the development of quantum computing systems utilising these components. In this work, an S-parameter measurement setup to characterise RF integrated circuits at milli-Kelvin temperatures has been proposed and for the first time, the S-parameter measurements at milli-Kelvin temperatures have been validated using two independent calibration techniques, thereby providing more confidence in measurements. The techniques are demonstrated experimentally by comparing and validating calibrated S-parameter measurements of a cryogenic attenuator integrated circuits at milli-Kelvin temperatures.
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 onedimensional 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 plasmonbased sources and detectors.
We investigate using finite element methods how sub‐micrometer to micrometer‐scale coplanar waveguide (CPW) can be used for the detection of fingerprint spectra of very small (of order 10−14 mL) volumes of analytes in the terahertz (THz) frequency range. The electric field distribution is investigated near the waveguide for various gap widths between the center conductor and ground plane using a finite element simulation (ANSYS High Frequency Structure Simulator, HFSS). Taking lactose monohydrate as an exemplar material, a Drude–Lorentz model is combined for its real and imaginary permittivities with this numerical simulation, finding a significant enhancement in fingerprint detection as the gap width is reduced; the electric field in the CPW is found to increase by a factor ≈14 times moving from a 20 to 0.5‐µm‐wide gap between center conductor and ground plane, while the on‐resonance THz absorption increases ≈14 times. The effective absorption coefficient of the lactose at 530 GHz is investigated as a function of the slot width for various lactose block thicknesses to understand how change in the field confinement and in the effective overlap between the lactose block and incident THz waves affect the effective absorption coefficient.
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