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Separating and detecting specific polarisations at multiple frequencies can be required for a number of scientific cases. However, in some cases, constraints on polarisation are defined by the choice of detectors used. In this paper we will present two devices that have been designed and built to increase performance when designing an optical system with these constrains. They are a polarisation sensitive...
We demonstrate that single-cycle intense terahertz (THz) pulses manipulate the motion of electrons in a single tunnel junction. By tuning the carrier-envelope phase of the THz pulses, the direction of the electron tunneling through the junction was coherently controlled either from the nanotip to the sample or vice versa. By analyzing the experimental data based on the Simmons model, we found that...
In this article we introduce a new type of frequency diverse antenna based on a leaky waveguide. We have shown with simulated experiment that the antenna can achieve 2cm spatial resolution at K-band frequencies.
Photoconductive antenna (PCA) array based THz near-field imager incorporating Hadamard multiplexing method is developed in this work. By using a 2 × 2 dipole antenna array as the THz transmitter, the system signal-to-noise ratio (SNR) is demonstrated to be improved by a factor of 2 as the theory predicts. Additionally, a 2-D scanning of a metallic structure on a THz-transparent substrate (with a total...
We demonstrate the applicability of shape memory alloys for creating THz plasmonic structures that can be reversibly reconfigured. This is accomplished by training nickel titanium alloy free-standing foils to have two bistable temperatures between which the physical structure can be switched thermally. Specifically, we show that the metal foil can be switched between a flat foil and one that has either...
Whether it is following electron ejection in water, probing hydrogen-bonding network dynamics of water or interactions of water-protein systems, time-resolved ultra-fast techniques in THz range are required. We present here our recent results from optical-pump THz-probe experiments [1], two-dimensional Raman-THz spectroscopy [2] as well as T-jump-THz experiments and discuss these advances also from...
We demonstrate that polarization-resolved THz cyclotron spectroscopy enables the transport properties of spin-split 2D heavy-holes in strained Ge quantum wells to be determined. The Rashba spin-orbit interaction strength is found from the magnetic-field dependence of the cyclotron frequencies. In high-mobility samples the optical quantum Hall effect is witnessed, where the transverse magnetoconductivity...
We report high-performance continuous-wave (C-W) THz quantum cascade lasers with semi-insulating surface-plasmon waveguide. Epitaxial-side down mounting process was developed to enhance heat extraction from the active region. C-W power above 100 mW and C-W wall-plug efficiency above 1.5% was obtained. The highest C-W operation temperature was 70 K.
In this study we present the direct terahertz time-domain spectroscopic measurement of CVD-grown multilayer graphene (MLG) on PVC substrate with an electrically tunable Fermi level. In a configuration consisting MLG and injected organic dopant, the transmitted intensity loss of terahertz radiation was observed with an applied voltage between 0 and 3.5 V. We showed that MLG on PVC devices provided...
The aim of the European project CONSORTIS is the development of a walk-by imaging system for concealed object detections working at submillimetre-wave frequencies. This imager will allow to image a full body at two frequency bands with high sensitivity (<1K) and large frame rate (10Hz). The imager relies on a large focal plane array with about 10k detectors operating at both bands coupled a common...
I will review the recent progress of semiconductor sources of terahertz radiation based on intra-cavity difference-frequency generation (DFG) in mid-infrared quantum cascade lasers (QCLs). These devices, referred to as THz DFG-QCLs, are similar in fabrication and operation simplicity to THz QCLs, but, unlike THz QCLs, they offer room-temperature operation and broadband spectral tuning in the entire...
We present the first experimental realization of a terahertz (THz) waveguide that exhibits a negative effective index of refraction. To demonstrate this, we designed fabricated and characterized a linear array of three-dimensional structures that consist of split ring resonators and posts. THz radiation is launched and guided in the form of surface plasmon polaritons (SPPs) along the 3D metallic structures...
It was reported that the human sweat ducts play a critical role in interaction of terahertz wave with human skin. Previously, we determined the resonant frequency of human sweat duct in axial mode of operation. In the study, we have investigated another mode of operation of human sweat duct known as normal mode of operation. Based upon the morphological features of human sweat duct obtained using...
THz spectroscopy and generation is performed in Rb0.94Mn[Fe(CN)6]0.98.0.3H2O Prussian-blue analogue. Our results indicate this cubic material has interesting photo-switchable nonlinear properties in the THz frequency range.
Controlling superpositions of electronic quantum states through nonlinear interactions is central to quantum computing. At THz frequencies, solid-state systems exhibit numerous elementary excitations suitable to this purpose, yet efficient dephasing mechanisms render their exploitation challenging. The cyclotron resonance, protected from Coulomb interactions by Kohn's theorem, is a unique exception...
We report on high-energy terahertz pulses by optical rectification (OR) in the organic crystal N-benzyl-2-methyl-4-nitroaniline (BNA) directly pumped by a conventional Ti:sapphire amplifier. The simple scheme provides an optical-to-terahertz conversion efficiency of 0.25% when pumped by collimated laser pulses with duration of 50 fs and a central wavelength of 800 nm. The maximum output energy and...
Spectral interference of two terahertz pulses emitting from laser plasmas induced by two successive femtosecond laser pulses in air is experimentally demonstrated. Here a leading pulse is set to be weaker than a trailing pulse and their temporal separation is larger than the pulse duration of the terahertz pulses. When the leading pulse is stronger than the trailing pulse, the frequency modulation...
By employing THz time-domain spectroscopy, far infrared optical properties of TmFeO3 single crystal are investigated schematically in temperature range from 5 to 300 K. The temperature dependence of resonances due to iron ions and Tm ions absorption due to crystal field are clarified. The experimental results demonstrate that the temperature induced spin reorientation transition (SRT) as well as crystal...
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