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We have addressed a very fundamental question, whether urea and guanidinium chloride (GdmCl) act as water ‘structure breakers’. Our study using THz time domain spectroscopy (TTDS) confirm that both these molecules perturb the extended solvation layer around themselves which supports the strongly debated “water structure breaker” notion of urea and GdmCl during their protein denaturation process[1,2].
We proposed and fabricated an oscillator array composed of three resonant-tunneling-diode terahertz oscillators integrated with slot-coupled patch antennas, which operates without the need for Si lens. We measured the radiation pattern for single and arrayed oscillators, and calculated the output power using the integration of the pattern. The output power of a single oscillator was ∼15 μW, while...
Scattering is an important phenomenon and distorts the THz absorption spectrum during analysis of materials. It is essential to understand how scattering from samples changes the THz signals. We presented an approach for estimating the relationship between scattering and granular sizes occurring in THz spectra. The samples were made of same solid material but in different granular sizes ranging from...
Project of powerful FEM operating from Ka- to W-band and aimed to accelerating applications is developed in collaboration between JINR (Dubna) and IAP RAS (N. Novgorod) based on linac LIU-3000. The key components to advance the JINR-IAP FEM into short wavelengths are short-period tapered wiggler, which is responsible for high-quality helical electron beam formation, and advanced Bragg resonator with...
The cocrystal of piracetam and 3-hydroxybenzoic acid under grinding condition has been characterized by terahertz spectroscopical technique. Spectral results show that the vibrational modes of the cocrystal are different from those of the corresponding parent materials. The dynamic process of such pharmaceutical cocrystal formation has also been monitored directly with THz spectra.
We present results of improvement of THz images registered at the frequency of 300 GHz. The improvement is achieved by processing of both phase and magnitude information provided by lock-in amplifier. The active imager uses a continuous-wave tunable radiation source. We investigate capabilities of utilizing phase and intensity information in order to obtain more accurate shape of object. Results of...
Photonic Bandgaps (Bragg reflectors) in moderately oversized corrugated waveguides can be applied as notch filters in the mm and sub-mm wavelength range. They offer unique options such as very steep frequency slopes, narrow or wide stop bands and very low insertion loss when compared to other technologies such as coupled cavity or Fabry-Pérot type filters. Also several defined stop bands within one...
A millimeter-wave wideband cylindrical dielectric resonator antenna (DRA) excited in its HEM113 and HEM115 modes is presented. The two modes are combined to widen the bandwidth, giving a wide 10-dB impedance bandwidth of more than 25%. The variation of the antenna gain is less than 3 dB across the impedance passband (|S11| < −10 dB).
Novel schemes for THz time-domain spectroscopy (THz-TDS) are suggested and approbated. Substantial improvement of the sensitivity compared to the standard electro-optic (EO) detection technique (at high frequencies) and to the previously shown technique based on laser pulse energy changes is demonstrated in experiment.
The field emission from the edge of vertically aligned reduced graphene oxide (rGO) film was examined experimentally. High current (I > 5 mA) and high emission current density (J > 100 A/cm2) was obtained using diode configuration. The thermal runaway of sharp protrusions on emission edge are considered to be source for the destructive vacuum breakdowns due to high local emission current. A...
We report a high efficiency, broadband terahertz (THz) modulator following a study of phthalocyanine-compound organic films irradiated with an external excitation laser. Both transmission and reflection modulations of each organic/silicon bilayers were measured using THz time-domain and continuous-wave systems. For very low intensities, the experimental results show that AlClPc/Si can achieve a high...
A strong-coupling five-gap barbell output cavity is investigated combined with the design of W-band sheet beam extended interaction klystron (SBEIK), which may have many advantages of resonant mode separation, gap fields coupling and RF energy exporting with high efficiency. Then the output cavity is used to construct a high gain W-band SBEIK with eight multiple-gap cavities. With the sheet beam voltage...
Employing a novel polarization-resolved detection, we precisely measured the polarization of terahertz emission from ionized gases in two-color field composed of circular polarized fundamental beam and linear polarized second harmonic. It shows that the polarization of the THz emission rotates with the phase delay and forms an attoclock. The polarization angular deviations of THz emissions in different...
In this work THz emission of the non-vertically aligned GaMnAs and InGaAs nanowires (NWs) were investigated for the first time. THz emission azimuthal dependencies on different nanowire layers were measured. In addition THz pulse amplitude dependencies on an angle between the incident laser beam and a normal to the sample surface were accomplished for the removed NW layer. The investigated layers...
Thin film grounded coplanar waveguides using Parylene-C and Cyclic-Olefin-Copolymer (COC) as low loss thin film have been fabricated and characterized up to 320 GHz. Attenuation around 1.75 dB/mm has been measured at 300 GHz with ∼5-μm-thick Parylene-C film, close to the attenuation obtained with Cyclo-Olefin Copolymer film of similar thickness.
We propose a leaky-wave antenna to generate circularly polarized highly directional terahertz beam using metamaterial scatters. A microstrip line is loaded with a series of complementary electric-LC and electric-LC resonators to generate respectively Ex and Ey components. The 900-phase difference and almost unity amplitude ratio of Ex and Ey are achieved by relative positioning of the resonators on...
The development of quantum cascade laser at ∼3.1 THz is reported. The material was designed with bound-to-continuum active region and grown by Veeco GEN-II solid source molecular beam epitaxy. Devices were processed using standard photolithography and wet chemical etching. Lasing is observed up to a heat-sink temperature of 110 K in pulsed mode with total light power above 1W at 10 K. A liquid nitrogen...
We present the first results of studying a pulsed (20 μs) discharge in nitrogen, which is produced by high-power (40 kW) focused beam of terahertz (0.67 THz) waves. The time dynamics of the discharge plasma glowing is studied in a wide range of wavelengths (300–650 nm) and gas pressures (0.5–350 Torr). An assumption is made about the determining role of long-living metastables of nitrogen N2 (A3Σu...
The dielectric properties of skin layers, which are the epidermis, dermis, and subcutaneous fat, were measured using several measurement systems. Measurements were conducted in vitro from 0.5 GHz to 1 THz. Measurement results indicated good agreement between each measurement system at a tissue temperature of approximately 35 oC.
The extended interaction oscillator (EIO) is considered to be a novel type of high power Terahertz (THz) source, which has a promising application prospects in Radar, medical imaging, etc. Up to now, CPI and other institutes have developed this type of EIO. The investigation on the J-band (220GHz-325GHz) EIO at the Institute of Electronics, Chinese Academy of Sciences (IECAS) is being developed. The...
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