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Surface wave provides unique applications ranging from biological sensing, deep-subwavelength lasing to plasmonic circuits. Seeking new approaches for controlling surface wave is highly desired in future integrated photonic devices. Here, we develop a versatile platform based on metasurfaces for the launch and control of propagating surface wave in the terahertz frequency regime.
We demonstrate that a nanostructured terahertz (THz) photoconductive detector enables sampling of THz fields localized on micrometer scale. The nanostructure, consisting of an optical nanoantenna array and a distributed Bragg reflector, acts as a hybrid cavity, which traps optical gate pulses within an optically thin photoconductive layer of the THz detector. This allows us to detect highly confined...
We present an electrically modulated nonlinear metamaterial at terahertz frequencies. The device consists of a planar array of split-ring resonators (SRRs) fabricated on n-type GaAs. Increasing the incident THz field strength induces carriers in the GaAs substrate, shorting the SRR capacitive gap and modulating the MM resonance. The application of a 15V bias to the MM reduces the net field modulation...
Several metasurface-based terahertz (THz) devices, including lens, computer generated holograms, spin selected focusing lens, as well as wavelength selected diffractive elements, have been designed and fabricated. The thickness of these device is only 1/4000 of the working wavelength. A THz focal plane imaging system is employed to characterize the function of the devices. Theoretical expectations...
A novel terahertz photoconductive antenna that totally suppresses unwanted echoes is demonstrated. This is achieved with a buried metal plane placed below the surface antenna structure and active layer, realizing a sub-wavelength cavity.
Bulk films and heterostructures based on HgCdTe compounds can be engineered to fabricate “gapped-at-will” structures. Therefore, 1D [1], 2D [2] and even 3D [3] massless particles can be observed in topological phase transitions driven by intrinsic (quantum well thickness, Cd content) and external (magnetic field, temperature or pressure) physical parameters. So far, the phases of 2D [1] and 3D [4]...
We have manufactured mid-infrared chalcogen donor centres in silicon by high-temperature diffusion doping. Electrical characterisation has shown that we can control the ratio of different donor centre concentrations. FT-IR spectroscopy reveals very narrow lines in the mid-infrared spectral band. We have now performed the first time-domain measurements on the donor centre excited states. Our preliminary...
CMOS-compatible, heavily-doped semiconductor films are very promising for applications in mid-infrared plasmonic devices because the real part of their dielectric function is negative and broadly tunable in this wavelength range. In this work we investigate n-type doped germanium epilayers grown on Si substrates. We design and realize Ge nano-antennas on Si substrates demonstrating the presence of...
We systematically studied the mid-20th century Italian oil panel painting “After Fishing” by Ausonino Tanda using x-ray transmission and terahertz time-domain transmission and reflection spectroscopic imaging (THz-TDSI).
On the basis of previous theoretical and experimental investigation there proposed and described the technical decision about examined possibility to do the receiver-frequency-meter-tuner of generators on the Josephson junctions (JJ) working in super wide band. It can be especially convenient for the experimental purposes with new generation structures when radiate power is small and frequency are...
A fast and continuous tuning of a 3.1-THz GaAs-based quantum-cascade laser is demonstrated. This is achieved by illuminating its rear facet with a high-power, near-infrared diode laser. The spectral position of the THz laser modes can be adjusted by the illumination power. The maximum tuning range achieved in pulsed mode at a temperature of 35 K is 9.1 GHz.
Density matrix model is developed for GaN-based two-well THz-QCLs. The optimized GaN/AlGaN two-well THz-QCL structure with a fixed aluminum composition is provided for a desired lasing frequency by calculations of all combinations of four layer thicknesses. The downhill simplex method is introduced when more parameters need to be optimized.
A conventional bull's eye antenna has a great potential to terahertz technologies, while its narrow band nature limits its ability for multi-frequency applications. Here we proposed an split-joint bull's eye (SJBE) structure with optimized aperture, which can achieve multi-frequency transmission and high concentration.
We report on the reflection properties of calibration targets required for calibrating the radiometric performance of the Microwave Sounder instruments for the MetOp-SG satellites prior to launch. Both fixed temperature, 80 K, and variable temperature, 80–315 K, targets are required to perform this task. The specifications, the preliminary baseline design of the target structure and its measured reflectivity...
In this work, we present a novel compact rectangular-waveguide-type (WR-12) coherent photonic mixer module, featuring a balanced photodetector. The module enables the direct fiber-to-the-antenna connectivity for the upcoming 5G links. Experimental results with respect to the output RF power (e.g., −7.3 dBm at 73 GHz) and the frequency response deviation (±0.5 dB) are presented within the 71–76 GHz...
The fabrication and testing of metal-insulator-metal (MIM) diodes on a flexible substrate for microwave and mm-wave applications are presented. The diodes utilized octadecyltrichlorosilane (OTS), which self assembles to form a thin, pin holes free insulator. Preliminary electrical analysis shows that the diodes have a typical zero bias resistance of approximately 80 kΩ, zero-bias curvature coefficient...
An ultrathin Terahertz (THz) quarter wave plate with high transmittance by flexible metamaterial is proposed in this paper. The device employs double layers of split ring resonator (SRR) with a polymer as the substrate. Due to the anisotropy of the SRR, it obtains a quarter wave plate with the transmittance of 0.72 and the ellipticity of 0.9994 at 0.854 THz from simulation. The device has a thickness...
This paper presents a broadband terahertz (THz) high-temperature superconducting (HTS) mixer based on a log-periodic antenna-coupled YBa2Cu3O7−x (YBCO) step-edge Josephson junction. The THz thin-film antenna, as well as the microwave coupling circuits, have been carefully designed to optimize the power transmission from and into the junction while realizing good isolation between the DC bias, local-oscillator...
A 340GHz backward wave oscillator (BWO) based on the sine waveguide and pencil electron beam is presented as a novel terahertz radiation source. The particle-in-cell (PIC) simulation results predicts that this device can produce the output power of over 2.7W in the frequency range of 335.8–348.5GHz by utilizing a 20mA pencil beam and adjusting the voltage from 12kV to 14 kV.
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