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We demonstrate and compare the use of Mach-Zehnder and the fiber based interferometer schemes in improving the performance of terahertz electric field measurements based on spectral-domain interferometry. The new schemes enable unlimited temporal scanning window without significant loss in the signal-to-noise ratio, thus overcoming a major limitation in conventional spectral-domain interferometry...
Conception of a hybrid type tilted-pulse-front pumping scheme for the generation of high-energy terahertz pulses is presented. The proposed setup is the combination of the conventional setup containing imaging optics and the contact grating. Calculation results for LiNbO3 and LiTaO3 terahertz generator crystals are presented.
Here the cyclotron electron beam (CEB) excitation of surface plasmon polaritons (SPPs) on the circular cylindrical structures is used to replace the linearly moving electron beam excitations. We have found that this change leads to essential consequence in physics for that there is natural periodicity of 2π in both circular cylindrical structure and CEB, and the combination of this dual natural periodicity...
The terahertz (THz) imaging enhanced with compact diffractive lenses and sensitive room temperature THz detectors was demonstrated to be suitable for carcinoma zones screening in bio-tissues. Optical transmission of the dehydrated histological sections with a colon cancer was measured with close to wavelength-limited spatial resolution at 0.6 THz frequencies. High number of the explicit areas where...
We report on THz emission from HgCdTe bulk films. Our experiments clearly show magnetically tunable THz emission that can be attributed to electron radiative recombination between the Landau levels (cyclotron emission). Energy band structure theoretical calculations using Kane Hamiltonian are performed. They allow identification of observed resonances as related to transitions between two lowest conduction...
Explosives detection has been performed in terahertz and Raman frequency bands using chemometric tools. We applied principal component models to compare the performances of terahertz and Raman spectra ibn explosives analysis, as well as binary and ternary explosive mixtures.
In 2003, we reported the first-ever development of a spectral imaging system using a terahertz (THz) wave parametric oscillator (TPO). The system has a dynamic range below four orders of magnitude, which enables it to identify reagents only through thin envelopes using spectral imaging. Recently, we succeeded in developing a high power and high sensitivity THz wave spectral imaging system using injection-seeded...
Problem of imaging of large-size week THz beams without energy losses on Novosibirsk free-electron laser has been solved by a large-aperture shot-focus aspherical lens and small-size pyroelectric camera Pyrocam III. Conditions of correct scale imaging were obtained by both the Gaussian beam's formalism and elementary diffraction theory.
Graphene, two-dimensionally arranged carbon atoms in honeycomb lattices, has unique optical properties due to its linear dispersion and the massless nature of its carriers. In this paper, we concerned with the spectrum analysis of monolayer graphene film. The pump light from 808 and 1064 nm infrared semiconductor laser with tunable power from 0 to 450mW incident on the samples respectively together...
In this work terahertz (THz) pulse emission of the non-vertically aligned GaAs core-shell nanowires (NWs) is investigated. THz emission azimuthal dependencies of different NW samples have been measured. It is shown that these measurements together with theoretical calculations could be a very promising method to determine the effective index of refraction (n0) of the NW ensemble. The measurement of...
Photoluminescence in n-doped GaAs/AlGaAs quantum well nanostructures has been studied experimentally in far-infrared (terahertz) spectral range under interband optical excitation at low lattice temperatures. Luminescence in the near-infrared spectral range related to the optical electron transitions from the donor ground state to the heavy hole subband along with interband electron-hole transitions...
Polar oxides are natural candidates for use in tunable mm-wave devices. Using different quasi-optical characterization setups, we present the complex dielectric constant of two ferroelectrics and the electrical tunability of one of them at 90GHz.
We describe experimental characterization of switchable THz metasurfaces using variable-angle broadband THz ellipsometry. A theoretical framework is used to extract surface susceptibility tensors as a function of frequency and applied DC bias. This will allow us to make a priori predictions of the performance of these devices for applications as metasurface active components.
Graphene's plasmons are extremely confined, with velocities as low as c/200, yet with long lifetimes exceeding 200 fs at room temperature. I will discuss recent experimental results in graphene plasmons in the frequency range 2–50 THz: how to engineer and understand their spatiotemporal dispersion, how to improve the lifetimes, and how plasmons may be optoelectronically detected using the graphene...
Compressive THz imaging holds the potential for increased spatial resolution and imaging speed when only a small number of detectors is available. The understanding of illumination patterns is essential in determining the performance for a compressive imaging setup. The results presented here start with an evaluation of the performance of different mask types. Then the influence of deviations of the...
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...
1-THz continuous-wave signal is generated by an optical frequency comb generator utilized as a 41st-order multiplier. Phase noise characteristics of generated signal are evaluated by heterodyne detector and microwave electrical spectrum analyzer.
Recent studies have shown that multiple terahertz pulses (T-rays) with several tens of micro joules can be generated from high-intensity, laser solid-density plasma interaction. Here we present experimental evidence of generation of milli-joule class multiple terahertz pulses from the rear side of a solid target during an interaction with high-power laser, along with a systematic study of THz yield...
A family of approaches employing sequences of optical pump pulses, yielding energy conversion efficiencies in the 5–10% range, is introduced. A method to generate these sequences by cascaded optical parametric amplification of narrowband pulses is discussed.
We propose an accurate permittivity imaging using terahertz continuous wave. A multi-tone unwrapped phase slope method is proposed to improve the accuracy. The measured permittivity error using the proposed method can be decreased by more than 1/3 and a more precise permittivity image can be acquired.
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