TeraFERMI is a beamline built up in 2015 at the Free Electron Laser (FEL) FERMI at Elettra in Trieste (Italy). FERMI is a seeded FEL that works in a single pass-single bunch mode at 10 or 50 Hz, covering the spectral range from 100 to 4 nm. TeraFERMI is based on a Coherent Transition Radiation source that provides high intense THz electric field in the multi MV/cm range. Such a THz electric...
Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have in the past two decades been increasingly employed to prepare various fascinating nonequilibrium states in matter. Superradiant Terahertz radiation from linear accelerators, first demonstrated in 2001 at Jefferson lab [1], is the working principle of a new class of...
The idea of building a 4th generation accelerator based light source at NCBJ has been developed for almost 20 years. The concept came to reality in 2018 after receiving the funding for the construction of the Polish Free Electron Laser – PolFEL (or formally, its first stage ). The PolFEL device will be driven with an RF continuous-wave superconducting linac, including a superconducting...
Polish Free Electron Laser (PolFEL) will be an accelerator based facility, which will provide researchers THz laser pulses with constant repetition rate of 50kHz. Maximum peak energy of these THz pulse (30µJ) and pulse duration (about 30ps) for such repetition rates are usually not achievable by typical optical laser sources. This parameters of PolFEL laser THz beam give big research...
Terahertz radiation lies at the boundary of two different domains—optics and electronics. This, still not fully explored, area entwines physical phenomena describing two permeating worlds and interfering laws of optics and electronics. The fusion of two superposing physical worlds becomes an enormous challenge in designing optical elements.
All types of optical structures have been implemented...
Intense narrowband terahertz pulses from the FELBE free-electron laser facility and a complementary table-top high-field THz source are utilized to study nonlinear excitation regimes of various degrees of freedom in semiconductors. In this talk we present several recent examples including impurity transitions in boron doped Si [1], intersubband transitions in Ge/SiGe quantum wells [2] and...
The Chemical Infrared Imaging (CIRI) /Solaris Advanced InfraRed beamline (SOLAIR) is currently under construction. The large radiation extraction from a bending magnet will allow to collect a very wide wavelength range (0.4 - 500 µm), covering the near (NIR),_mid (MIR) and the far (FIR) infrared spectral range. The extraction of infrared range of synchrotron radiation will be achieved using a...
The results of optical magneto-spectroscopy study (Raman scattering, THz absorption, high frequency magnetic resonance) of layered MnPS3 and FePS3 antiferromagnets will be presented. Attention will be focused on magneto-elastic interaction in MnPS3 [1] and appearance of magnon polarons in FePS3 [2]. Besides, the origin of a magnon gap in MnPS3 and splitting of this gap observed in both...
In the regime of strong light-matter coupling, polariton modes are formed that are hybrid light-matter excitations sharing properties of both, an electrodynamic cavity mode and a matter mode. Recently, magnon-polaritons are intensively researched in ferromagnetic materials in the microwave range, with potential applications for quantum computing and sensors. In the recent decade, polaritons...
We present an overview that sheds light into the carrier dynamics of in Landau-quantized Dirac and Kane systems, namely graphene and mercury cadmium telluride (MCT). The non-equidistant Landau-ladder makes these materials highly attractive for realizing the old dream of the semiconductor physics community to fabricate a Landau-level laser. For a recent review on this topic, see Ref. [1]. In...
The main inspiration of the current work was the results previously obtained by the part of the co-authors in MCT samples by temperature-dependent THz magnetospectroscopy [1]. The latter revealed the evolution of the energy band-gap with temperature vanishing at a certain temperature. It was shown that although the fermions in MCT alloys are represented by the admixture between the Dirac and...
The temperature dependences of photo-response in sub-THz regime (0.14 THz) of AlGaN/GaN and graphene transistors were studied at temperatures from 10 to 300 K. Instead of measuring the voltage response using a lock-in amplifier, the current induced by the incoming sub-THz radiations was measured directly using the semiconductor parameters analyzer (SPA). This approach allows fast and multiple...
Semiconductor superlattices -- artificial periodic structures consisting of ultrathin layers where by variation of their width, doping level and profile one can tailor their optical and electronic properties in a desirable way – can be found as an attractive environment to investigate various high-frequency phenomena [1,2].
In the given communication, we present the first experimental...
Future wireless technologies will require very high data rates and low latency to satisfy the nearly exponential growth of worldwide data traffic [1]. Terahertz (THz) technologies with its broad unallocated frequency band (0.1‑10 THz) can be a promising potential solution. Along with extreme densification of the infrastructure and highly directional beams, it is the key enabling technology of...
High electron mobility and temperature stability of III-nitride heterostructures serve as a base for the development of tunable frequency THz emitters. Some THz emission results of the 2D plasmons in nitride high electron mobility transistor (HEMT) structures have been previously reported, but they are still far from commercially viable devices. It is worth noting that the graphene-based...
Pursuit after new technical and scientific achievement is a driving force for new solutions in research equipment. Furthermore, highest ever competition is pushing time of rapid development to the limits. Evolution of science lead us to a place where two or more IR radiation wavelengths are necessary to conduct some experiments. In some cases wavelength separation is significant, mixing one...
The accurate knowledge of constitutive parameters of dielectric materials is demanded in numerous applications, from designing quasi-optical components, antennas and sensors to nondestructive testing. Terahertz time-domain spectroscopy (THz-TDS) is a recognized technique of the broadband material characterization, but it requires a well-adjusted measurement setup, special sample holders etc....
We report on the investigations of FinFET and EdeFET AlGaN/GaN field effect transistors as THz detectors. Both devices we fabricated in the same technological runs on the base of the two-dimensional electron gas (2DEG) AlGaN/GaN epitaxial structures and then investigated towards THz detection. Design of a new FET dubbed EdgeFET is based on two lateral Schottky barrier gates on the sides of...
The mm-wave and terahertz (THz) frequency ranges are gaining much attention recently due to their high applicability, which creates a need for the development of the devices operating in abovementioned frequency ranges. One among the most important elements of such THz devices (e. g. Phase shifters) are varactors (variable capacitors), that allow tuning of the system via electrically-induced...
We present results of magnetotransport and magnetospectroscopic studies on a single CdTe quantum well (QW) with Cd$_{0.8}$Mg$_{0.2}$Te barriers modulation-doped with Iodine donors. Experiments were carried out at temperatures of about 1.8 K as a function of magnetic field up to 10 T and included measurements of: transport, THz transmission, photoluminescence, optically detected cyclotron...
Based on the experimental small-field magnetotransport measurements performed for 7.1 nm-width HgCdTe/HgTe/HgCdTe quantum well with inverted band structure order, we will present results of the mobility spectra analysis in dependence on both the gate voltage (charge carrier concentration) and temperature.
We will discuss these data from the point of view of the band structure picture and...
Currently developed free electron lasers facilities more and more frequently use superconducting elements in theirs advanced constructions. Most frequent examples of these applications are the superconducting electromagnets, current leads to them and especially superconducting cavities. The same concerns the superconducting shields, as well as superconducting correction coils conducting the...
We report on THz characterization of graphene composites in the extended THF band from 0.25 to 4.00 THz. The composites, containing low percent by weight fractions (wt.%) of graphene form 0.8wt.% to 1.2wt.%, were investigated using THz- Time Domain Spectroscopy (THz-TDS). Based on the measured transmission and reflection coefficients, the shielding effectiveness parameters of reflection (SER)...
Terahertz (THz) systems and technology have become of large interest over the last 20 years. However, it still needs new and innovative solutions in the field of both generation and detection of THz radiation. Despite the fact that scientists in many research centers are constantly working on the production of new THz sources and detectors based on semiconductors such as silicon, it turn out...
In recent years, terahertz (THz) techniques have been used in many fields of applications, most of all in space, telecommunication and security industry. However, the number of projects connecting THz technologies with Science and Culture is constantly increasing and the conservation and restoration of art, e.g. paintings or sculptures, belongs to the most evolving areas in this domain.
The...
The Inverse Faraday Effect (IFE) is the appearance of stationary magnetic moments magnetization caused by circulary polarized ligh. Up to this moment, IFE has been mostly studied in the magnetic materials. In recent years, the IFE was predicted in the periodic lattice of metallic disks or spheres placed in the vicinity of two-dimensional electron liquid and under illumination of the external...
The rapid development of modern 5G and 6G communication systems is connected with a increasing demand for new dielectric substrate materials, which should provide higher signal transmission speed and miniaturization as well as possibility of passive component integration. Requirements for such new materials include a low dielectric constant to minimize signal propagation delay, low dielectric...
The research and development in the frequency region of 0.1-1.0 THz is extremely significant for the wide range of applications, such as telecommunication and imaging systems, material spectroscopy, medical imaging and treatments, etc. Despite the problems in technology and high prices for basic components (phase shifters, directional couplers, etc.), the THz systems offer higher date rates...
Antiferromagnets are ideal candidates to reach THz landmark in data storage with no additional energy costs. However, the lack of a net magnetization in these materials requires exceedingly high magnetic fields to manipulate their spins, hindering not only applications, but even fundamental studies on writing bits on antiferromagnets. Here we propose an approach to empower THz control of...
The conductivity of polycrystalline graphene in the THz range is relevant for many applications. However, a full understanding of the underlying physics has not yet been achieved, due to the lack of reliable models of carrier transport in polycrystalline nanomaterials. In this work, we relate the structural deformation in strained graphene with the deviation from the Drude conductance. To this...
Graphene is a very versatile material for optoelectronics or nonlinear optics in a large spectral range, in particular for THz radiation. One drawback is the low interaction volume between THz radiation and the single atomic layer, which limits the light matter interaction at elevated photon frequencies. During the recent years it has been shown that patterning graphene into plasmonic...
More than 40 years ago, a new direction in physics opened up with the arrival of plasma-wave electronics. The possibility that the plasma waves could propagate faster than electrons fascinated all. Therefore, it was initially expected that plasmonic devices, including detectors and generators of electromagnetic radiation, would be able to work effectively in the very high frequencies -...
During the last decade, field-effect-transistor-based terahertz detectors (TeraFETs) have been developed to the competitive technology which enables a variety of new applications in the THz frequency range [1]. Among the achieved state-of-the-art performance [2] TeraFETs can also exhibit a strong nonlinear response to intense THz radiation pulses [3]. We show that the character of nonlinearity...
Water is one of the most studied and least understood liquids[1]. While several anomalies in the thermodynamic, macroscopic properties of water are well documented[2], on the microscopic scale this special liquid is characterized by a dynamic, tetrahedral network of hydrogen bonded (HB) molecules rearranging on the picosecond timescale[3]. Thus, terahertz (THz) spectroscopy is uniquely suited...
We report on the technology and THz spectroscopy of 2D plasmonic devices based on high density two-dimensional electron plasma in AlGaN/GaN semiconductor heterostructures. The devices were fabricated in the geometry of field effect transistor (FET). For the efficient coupling between long wavelength THz radiation and short wavelength 2D plasma waves, the special metallic, periodic grating-gate...
Intelligent (smart) or adaptive antennas are the most suitable for wireless communication, especially for fifth generation and higher communication systems. The key property of intelligent technology is the ability to respond automatically by changing an appropriate radiation pattern. Phase-array based smart antennas are used as the main beamforming structure. The development and application...
Almost twenty years ago, experiments on high-mobility GaAs/AlGaAs heterostructures revealed strong magnetoresistance oscillations excited by microwave illumination [2,3]. These oscillations are $2\pi$-periodic in $B_\mathrm{CR}/B\equiv\omega/\omega_c$, and thus reflect commensurability between the photon energy $\hbar\omega$ and separation $\hbar\omega_c$ between neighboring Landau levels [4]....
Low-loss materials find multiple applications in the modern electronics industry with dielectric-based substrates used in printed circuit boards (PCB’s) being a prominent example. Others include ceramic materials and plastics employed in packages for integrated circuits or supportive and protection structures for integrated antennas. There is a strong interest in efficient and easy-to-use...
Historically, terahertz science and technology has been restricted to specialized applications such as radio astronomy due to various technological challenges. Hollow rectangular waveguides are the primary transmission line medium in many terahertz systems due to their mechanical stability, low electromagnetic losses, enclosed nature, and compatibility with active circuit elements....
Terahertz Time-Domain Spectroscopy (THz-TDS) has recently become an attractive analytical technique in gas, liquid or solid state phase which uses ultra-short bursts of terahertz radiation for probing of the medium properties. We show that straight forward and fast determination of propagation times of THz pulses transmitted through gasoline samples is adequate to detect small, a few hundred...
Physics of coupling of resonating structures has been investigated for many decades, yet still new effects are discovered due to the better understanding of the underlying processes and due to the shift of the focus from the classical resonators to the quantum objects, to meta-atoms and to the nanoscale in general. The well-known effect in atomic physics of the electromagnetically induced...
The so-called "terahertz gap" is gradually being filled with new compact devices and effective solutions for the detection and emission of radiation. In particular, the development of field-effect-transistors (FET) is starting to play a significant role in this process [1, 2] and had demonstrated in applications together with pulse free electron lasers and gas laser [3, 4] and fast...
The non-ionizing nature of terahertz radiation together with the ability to penetrate through common packaging materials have sparked significant interest in THz non-destructive imaging applications. There is a huge need for low-cost and compact THz systems, which will grow with the further discovery of potential THz wave applications. A natural solution to this issue is the usage of...
Terahertz (THz) radiation brings the attention of researchers and entrepreneurs for at least a few decades and has already found numerous applications in various areas, such as medical diagnostics, nondestructive testing, detection of dangerous materials and objects, security or telecommunication. This work focuses on the latter area of potential applications and aims at the development of the...
The four FELs at the HFML-FELIX user facility (FELIX-1, FELIX-2, FELICE and FLARE) each produce their own range of wavelengths and together they provide a tuning range between 3 and 1500 micrometer (0.2-110 THz). FELICE is a unique FEL beamline dedicated to intra-cavity experiments: the intensity at the point of the experiments is 50 to 100 times higher compared to the conventional user...
The FELBE User Facility at the ELBE Center for High-Power Radiation Sources offers a pair of FELs that deliver beam to eight different user labs. The FELs are driven by a two-stage Superconducting RF (SRF) linac, which produces a quasi-CW beam (13 MHz/1 mA) at an energy of up to 36 MeV. The tuning range spanned by the two FELs extends from the mid IR to THz (5 – 250 μm). The spectral range...
