2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)
Radiometry experiments, performed on human subjects, show that in the vicinity of a central frequency of 507 GHz the emission of the human skin is substantially nonequilibrium in its nature. The intensity of the radiation registered using a superconducting integrated receiver (SIR) , was correlated with the level of the physical and mental stress of subject under examination. This result suggests that human skin may generate sub-THz waves.
In this paper, the dispersion characteristics of slow-wave structures suitable for use in devices in the terahertz range are calculated. Slow-wave structures of “winding waveguide” and “counter pins” types can be considered as suitable systems. Analysis of dispersion characteristics of slow-wave structure was carried out by a waveguide-resonator model, which is built for the slow-wave structure of “winding waveguide”-type taking into account a channel for the electron beam. Waveguide-resonator model is consisted of quadripoles which describe the waveguide segments. This model is most accurately reflects the structure of the field in the winding waveguide. Dispersion characteristics were calculated according to the program stated in this paper. These characteristics are used to construct model of millimeter traveling-wave tube, which is in this case the chain of quadripoles. The most common in the solution of these problems is the discrete approach . The difference form of electrodynamic theory of excitation is used to justify the use of a mathematical model of the discrete interaction description .
Achievement of the ultimate sensitivity along with a high spectral resolution is one of the frequently addressed problems, as the complication of the applied and fundamental scientific tasks being explored is growing up gradually. In our work, we have investigated performance of a superconducting nanowire photon-counting detector operating in the coherent mode for detection of weak signals at the telecommunication wavelength. Quantum-noise limited sensitivity of the detector was ensured by the nature of the photon-counting detection and restricted by the quantum efficiency of the detector only. Spectral resolution given by the heterodyne technique and was defined by the linewidth and stability of the Local Oscillator (LO). Response bandwidth was found to coincide with the detector's pulse width, which, in turn, could be controlled by the nanowire length. In addition, the system noise bandwidth was shown to be governed by the electronics/lab equipment, and the detector noise bandwidth is predicted to depend on its jitter. As have been demonstrated, a very small amount of the LO power (of the order of a few picowatts down to hundreds of femtowatts) was required for sufficient detection of the test signal, and eventual optimization could lead to further reduction of the LO power required, which would perfectly suit for the foreseen development of receiver matrices and the need for detection of ultra-low signals at a level of less-than-one-photon per second.
The fifth generation wireless systems are expected to rely on a large number of small cells to massively offload traffic from the cellular and even from the wireless local area networks. To enable this functionality, mm-wave (EHF) and Terahertz (THF) bands are being actively explored. These bands are characterized by unique propagation properties compared with microwave systems. As a result, the interference structure in these systems could be principally different to what we observed so far at lower frequencies. In this paper, using the tools of stochastic geometry, we study the systems operating in the EHF/THF bands by explicitly capturing three phenomena inherent for these frequencies: 1) high directivity of the transmit and receive antennas; 2) molecular absorption; and 3) blocking of high-frequency radiation. We also define and compare two different antenna radiation pattern models. The metrics of interest are the mean interference and the signal-to-interference-plus-noise (SINR) ratio at the receiver. Our results reveal that: 1) for the same total emitted energy by a Poisson field of interferers, both the interference and SINR significantly increase when simultaneously both transmit and receive antennas are directive and 2) blocking has a profound impact on the interference and SINR creating much more favorable conditions for communications compared with no blocking case.
Interest in research in the terahertz range is driven by a great number of various applications, where terahertz instruments may play a leading role. To name just a few, such applications include study of the cosmic microwave background radiation and the distribution of the dark matter, medicine, navigation, fire alarm, security systems and environmental monitoring. The paper discusses the possibility of using a receiver based on the hot-electron effect in superconducting films as an imaging system. We present the results of the noise equivalent temperature difference (NETD) measurements performed with a hot-electron bolometer mixer made from a thin superconducting film. The receiver with a noise temperature of ~ 3800 K at a local oscillator frequency of 300 GHz a bandwidth of 500 MHz and an integration time of 1 s has offered an NETD of 0.5 K. We have also developed a technique that enabled us to reduce the contribution of the mixer gain fluctuations to the overall system instability. As of this writing, the above value of the NETD is the lowest value offered for this type of receiver, which indicates the possibility to use such receivers in real-time imaging systems. The technique offered in the paper for achieving the limiting value of the NETD offers an alternative to the phase-locking scheme.
In this paper, dispersion characteristics of "serpentine”-type slow-wave structures, which are promising for the terahertz range use, are calculated. For 3D-modeling, HFSS was used. Program described in work was used in the calculation. Using the obtained characteristics, octopole chain model of the slow-wave structure is constructed. Discrete approach is advisable in solving these problems. Justification of the applied mathematical model for the discrete interaction follows from the difference form of electrodynamic theory of excitation . Requirements to coefficients of the resulting finite-difference equation are high, because their accuracy determines how close the mathematical model of the discrete interaction to the physical laws is. These coefficients have a certain electrodynamic sense and are obtained through the octopole transmission matrix coefficients. In turn, this octopole is a mathematical model of the resonator slow-wave structure cell.
Carbon nanotubes (CNTs) have recently been integrated into optical waveguides and operated as electrically-driven light emitters under constant electrical bias. Such devices are of interest for the conversion of fast electrical signals into optical ones within a nanophotonic circuit. Here, we demonstrate that waveguide-integrated single-walled CNTs are promising high-speed transducers for light-pulse generation in the gigahertz range. Using a scalable fabrication approach we realize hybrid CNT-based nanophotonic devices, which generate optical pulse trains in the range from 200 kHz to 2 GHz with decay times below 80 ps. Our results illustrate the potential of CNTs for hybrid optoelectronic systems and nanoscale on-chip light sources.
This volume presents new results in the study and optimization of information transmission models in telecommunication networks using different approaches, mainly based on theiries of queueing systems and queueing networks .
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.