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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]...
In a first part, we are reporting on high-7c superconducting (YBCO) hot electron bolometers for high sensitivity and ultra-wide bandwidth terahertz heterodyne mixing and passive imaging. Here applications are sought in space programs as well as in civil security. In a second part, we are reporting on pyroelectric detectors using amorphous semiconducting (i.e., oxygen depleted) YBCO films; various...
Broadband terahertz time domain spectroscopy (THz-TDS) and time resolved terahertz spectroscopy (TRTS) were performed on a 54 μm thick chalcogenide glass (As30Se30Te40) sample using a two-color laser induced air plasma THz system in transmission and reflection configurations, respectively. Two absorption modes were observed at 2–3 THz and 5–8 THz. The photo-induced conductivity can be well described...
Single-shot detection of a terahertz (THz) electric-field transient has been demonstrated using a high-bandwidth oscilloscope. The THz modulation was imprinted on a chirped picosecond probe pulse via an electro-optic crystal, and the probe pulse was subsequently temporally expanded to nanosecond time scales using the group velocity dispersion of a long optical fiber. The resulting GHz modulation on...
We compare two methods of wavefront analysis of THz pulses associated with a 2D electro-optic imaging system. The first one is the standard Hartmann sensor, and the second one is based on the well-known fact that EO sampling can record the phase variation of the THz electric field.
In order to realize pulsed ESR measurements by using a gyrotron oscillator. 154 GHz gyrotron output had been successfully sliced to intense and short millimeter wave pulses. A quasi-optical transmission system has been developed to be led these short pulses to ESR measurement probe.
Self-detection is demonstrated as a simplifying new operation mode of scattering-type near-field optical microscopy (s-SNOM) in the mid infrared (6.2 μm wavelength). The back-scattered light from a tapping AFM tip is fed back into the quantum cascade laser used as illumination source such that recording of the laser voltage, at harmonics of the tapping frequency, generates amplitude and phase near-field...
In the THz spectral region quantum detectors are intrinsically limited by the small energy of the electronic transition involved in photon absorption. To overcome this problem and improve detector performances, we propose novel approaches in which concepts borrowed from high frequency electronics and metamaterials are exploited to realize THz detectors. In particular, we have investigated sub-wavelength...
Based on a number of inquiries from the industrial community Terasense has developed and started production of a new terahertz imaging system. The system is designed for a conveyor based non-destructive testing and security scanning applications. The imaging kit includes 1×256 pixel THz linear camera and 100 GHz (80 mW) source with a special projection optics. The terahertz imaging system has undergone...
We experimentally demonstrate ultrafast terahertz induced demagnetization in conducting ferromagnets, Ni, Co, and Fe. At even higher excitation fluence, the materials lose their magnetic properties and then get damaged before magnetic switching takes place [1].
We discuss how noncontact, quantitative large-area mapping of the conductance of thin films requires delicate corrections in order to deduce electrical properties such as graphene mobility from THz-TDS measurements.
We report on the influence of substrate thickness on the performance of antenna coupled microbolometers for terahertz (THz) detection. Planar antennas with NbsNó microbolometers were fabricated on silicon substrates. Detected voltages of these antenna-coupled microbolometers are altered with a periodic variation from 0.5 THz to 0.75 THz, which is accorded with the reflection of the substrate. By placing...
A time-domain approach that gives access to the quantum properties of light and possibly other fundamental excitations in condensed matter is presented, covering the entire mid-infrared and terahertz frequency ranges. Ultrabroadband electro-optic sampling with few-femtosecond and highly stable laser pulses allows direct detection of the vacuum fluctuations of the electric field in free space [1,2]...
The report analyzes the perspective of non-canonical version of gyrotrons in terms of possibility of frequency tuning and improved mode selection at gyrotrons working on the cyclotron frequency harmonics.
Terahertz (THz) sideband generation on a near-infrared (NIR) carrier has been recently demonstrated using quantum cascade lasers (QCL), with potential applications in wavelength shifting and THz up-conversion. However, the NIR wavelength range and nonlinear efficiency were severely limited by absorption. Here we overcome this drawback through a novel reflection geometry, whilst preserving a large...
Mid-infrared, Far-infrared, and terahertz bands (wavelength λ ≈ 3 μm ∼ 3 mm in vacuum) in electromagnetic spectrum have many important applications, for example, remote sensing, homeland security, health and medicine, cosmology, and free-space communication. During the past thirty years, essential progress has been made in radiation sources, detectors and their arrays, functional devices, and application...
Ac conductivity and dielectric permittivity of bovine serum albumin, cytochrome c and extracellular matrix synthesized by electrogenic bacteria Shewanella oneidensis MR-1 are measured at frequencies 1–1012 Hz and temperatures 10–300 K. Two types of conductivity mechanisms are observed as well as nearly constant loss (NCL) phenomenon, universal dielectric response (UDR) and signatures of boson peak...
A periodic train of powerful ultrashort microwave pulses can be generated in electron oscillators with a saturable absorber installed in the feedback loop. This method of pulse formation is similar to the passive mode-locking widely used in laser physics where such pulses are also treated as dissipative solitons. We consider the method of mode-locking applied to different types of microwave amplifiers...
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