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Most semiconductors have surface dynamics radically different from its bulk counterpart due to the surface state. However, direct observation of the surface carrier dynamics has been limited to nano structures where the surface-to-volume ratio is very high. Here, we develop a new type of terahertz (THz) nanoscopy to investigate surface dynamics of bulk semiconductors, using metallic nano gap accompanying...
We present an investigation related with the use of sialic acid as an auxiliary indicator for the early detection of diseases by using Terahertz Frequency-Domain Spectroscopy (THz-FDS) Technique. We propose the characterization of thin films of N-Acetylneuraminic acid-synthetic, >95% and add in colloidal solution nanoparticles of Ag (Ag-NPs) and Au (Au-NPs) in order to increase the superficial...
Metal-stripe surface grating structure presents a stable single-mode operation for THz quantum cascade lasers due to its strong coupling mechanism and easy tuning. We use sampled metal-stripe gratings to establish a distributed feedback and scale the single-mode power by tune the grating parameters. Record single-mode power more than 500 mW at 10 K is achieved.
Dispersion compensation is vital for the generation of ultrashort and single cycle pulses from modelocked lasers across the electromagnetic spectrum. However, no such scheme have been successfully applied to terahertz (THz) quantum cascade lasers (QCL) for short and stable pulse generation in the THz range. Here we show a monolithic on-chip compensation scheme for a modelocked QCL, permitting THz...
We establish a one-to-one mapping between the local phase slip and the spatial position near the focus by scanning a thin jet along the propagation direction of laser beams. The measurement shows that the optimal phase of THz can be utilized to characterize in situ the spatially dependent relative phase of the two-color field and the carrier-envelope-phase of the few-cycle pulse. The result is of...
THz transmission spectra of the commonly used pain killers-aspirin and paracetamol were measured using the FTIR technique and calculated using the density functional theory method. Despite the shift in the frequencies, there are common absorption bands between these compounds. The common bands were established to be primarily due to the various movements of the benzene ring.
Phaselock technique is used to improve the resolution of the phase delay for THz generation in two-color laser field, which leads a high resolution up to several microradians. The results show that the optimal phase delay shifts slightly with the experimental conditions changing.
Cancer is defined as a genetic and epigenetic disease involving the chemical and structural alteration of DNA. Because optical techniques measure overlapped and synthetic signals of materials, regardless of “ordering” features (such as the nucleotide order of a DNA sequence), it is difficult to sequence a genome to detect cancerous genetic changes using optical techniques. For this reason, previous...
Terahertz (THz) imaging and tomography are modern imaging techniques allowing 2D and 3D inspection of objects over a broadband frequency range. However, the transfer of this technique to medical applications is limited to surface or subsurface inspection due to the large concentration of water molecules which are an intrinsic characteristic of biological tissues. Then, we report the results of investigations...
Interdigitated photoconductive (IPC) switches are convenient sources and detectors for terahertz (THz) time domain spectroscopy. However, reflection of the emitted or detected radiation within the device substrate can lead to echoes that inherently limits the spectroscopic resolution achievable. In this work, we design and realize low-temperature-grown-GaAs (LT-GaAs) IPC switches for THz pulse generation...
Oscillation of 1MW at quad-frequency 203GHz, 170 GHz, 137GHz and 104GHz were demonstrated with a high-order mode (TE31,11) gyrotron developed for ITER. The final design of the ITER equatorial launcher has being implemented. The RF prototype testing to validate the millimeter wave design of the launcher were carried out and the results confirmed the steering range and quality of mm-wave beam and in-directly...
Compact laser-produced plasma sources have carved their niche in high-power terahertz generation, thanks to the intense work carried out by various research groups around the world. Solid targets are preferred as interaction medium due to their high electron density and ability to sustain strong currents and electric fields, thereby generating millijoule, broadband terahertz pulses with no known upper...
More and more uncooled terahertz (THz) real-time imaging cameras are being developed and commercialized. For image analysis, the characterization of the optical performance is an important issue. We tested the TZCam camera that integrates the CEA-Leti based on micro-bolometer array coupled to antennas and a resonant cavity structure, and equipped with a terahertz objective. A numerical tool kit has...
The paper describes recent results of theoretical and experimental studies of powerful relativistic masers based on linac LIU-3000. The key components of the oscillators are advanced Bragg resonators based on coupling of propagating and quasi-cutoff waves that possess high selectivity over transverse coordinates and allows establishment of narrow-band operating regime in strongly oversized system...
Reliable doping in semiconductor nanowires is essential for the development of novel optoelectronic devices. Dopant incorporation within the nanowire can allow for optimisation of key optoelectronic properties, such as electron mobility and carrier lifetime. Thus, in-depth characterisation of doping mechanisms in semiconductor nanowires and their effect on the nanowire optoelectronics properties is...
A parallel-plate waveguide (PPWG) is attracting interest as a guide medium in the terahertz region. The PPWG does not need extremely high manufacturing precision, and can even operate at short wavelength electromagnetic waves. In this study, the effect of a waveguide structure for the electric-field enhancement and loss in a tapered PPWG is analyzed by the finite-difference time-domain method, and...
We performed large scale classical molecular dynamics simulations (MDS) of a solvated microtubule (MT) composed of 42 tubulin heterodimers to examine vibrational energy absorption and dissipation mechanisms, and to describe the expected behavior of the MT following terahertz (THz) excitation. We computed MT absorption spectra and vibrational density of states in the THz regime, and performed an analysis...
We demonstrate a novel approach to the problem of express diagnostics based on THz spectral features of the breast cancer and THz emission and detection provided by the topological edge channels of silicon nanosandwich-structures.
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. Preliminary cw-ESR measurements had been successfully performed for DPPH from the room temperature down to the liquid...
A new real time control system is being installed on the Electron Cyclotron (EC) heating system at the DIII-D tokamak, which opens new possibilities for plasma experiments while increasing the gyrotron system reliability. The control system allows restarting the gyrotrons after an incipient fault is detected and cleared. The EC installation is being used for a wide variety of experiments requiring...
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