49 research outputs found
Optical response of a cold-electron bolometer array
A multielement bolometric receiver system has been developed to measure the power and polarization of radiation at a calculated frequency of 345 GHz. Arrays of ten series-parallel connected cold-electron bolometers have been pairwise integrated into orthogonal ports of a cross-slot antenna. Arrays are connected in parallel in the high-frequency input signal and in series in the output signal, which is measured at a low frequency, and in a dc bias. Such an array makes it possible to increase the output resistance by two orders of magnitude as compared to an individual bolometer under the same conditions of high-frequency matching and to optimize the matching with the JFET amplifier impedance up to dozens of megohms. Parallel connection ensures matching of the input signal to the cross-slot antenna with an impedance of 30 Omega on a massive silicon dielectric lens. At a temperature of 100 mK, a response to the thermal radiation of a thermal radiation source with an emissivity of 0.3, which covers the input aperture of the antenna and is heated to 3 K, is 25 mu V/K. Taking into account real noise, the optical fluctuation dc sensitivity is 5 mK, the estimated sensitivity corresponding to the noise of the amplifier is about 10(-4) K/Hz(1/2), and the noise-equivalent power is about (1-5) x 10(-17) W/Hz(1/2)
On-chip coherent detection with quantum limited sensitivity
While single photon detectors provide superior intensity sensitivity, spectral resolution is usually lost after the detection event. Yet for applications in low signal infrared spectroscopy recovering information about the photon’s frequency contributions is essential. Here we use highly efficient waveguide integrated superconducting single-photon detectors for on-chip coherent detection. In a single nanophotonic device, we demonstrate both single-photon counting with up to 86% on-chip detection efficiency, as well as heterodyne coherent detection with spectral resolution f/∆f exceeding 1011. By mixing a local oscillator with the single photon signal field, we observe frequency modulation at the intermediate frequency with ultra-low local oscillator power in the femto-Watt range. By optimizing the nanowire geometry and the working parameters of the detection scheme, we reach quantum-limited sensitivity. Our approach enables to realize matrix integrated heterodyne nanophotonic devices in the C-band wavelength range, for classical and quantum optics applications where single-photon counting as well as high spectral resolution are required simultaneously
Electron energy relaxation in disordered superconducting NbN films
We report onthe energy relaxation of electrons studied by means of magnetoconductance and photoresponse in a series of superconducting NbN film with thickness in the range from 3 to 33 nm. The inelastic scattering rate of electrons on phonons obeys Tntemperature dependence where the exponent is in the range ????≈3.2÷3.8and shows no systematically dependence on the degree of disorder. At 11K electron-phonon scattering times are in the range11.9 -17.5 ps.We show that in the studied NbN films the Debye temperature and the densityof phononstatesare both reduced with respect to bulk material. In the thinnest studied films reduced density of states along with the phonon trapping slowsdown the energy relaxationofelectrons by afactor of 4 as compared to the prediction of the tree dimensional phonon mode
Electron energy relaxation in disordered superconducting NbN films
We report on the inelastic-scattering rate of electrons on phonons and
relaxation of electron energy studied by means of magnetoconductance, and
photoresponse, respectively, in a series of strongly disordered superconducting
NbN films. The studied films with thicknesses in the range from 3 to 33 nm are
characterized by different Ioffe-Regel parameters but an almost constant
product q_Tl(q_T is the wave vector of thermal phonons and l is the elastic
mean free path of electrons). In the temperature range 14-30 K, the
electron-phonon scattering rates obey temperature dependencies close to the
power law 1/\tau_{e-ph} \sim T^n with the exponents n = 3.2-3.8. We found that
in this temperature range \tau_{e-ph} and n of studied films vary weakly with
the thickness and square resistance. At 10 K electron-phonon scattering times
are in the range 11.9-17.5 ps. The data extracted from magnetoconductance
measurements were used to describe the experimental photoresponse with the
two-temperature model. For thick films, the photoresponse is reasonably well
described without fitting parameters, however, for thinner films, the fit
requires a smaller heat capacity of phonons. We attribute this finding to the
reduced density of phonon states in thin films at low temperatures. We also
show that the estimated Debye temperature in the studied NbN films is
noticeably smaller than in bulk material.Comment: 23 pages, 6 figure
Superconducting parallel nanowire detector with photon number resolving functionality
We present a new photon number resolving detector (PNR), the Parallel
Nanowire Detector (PND), which uses spatial multiplexing on a subwavelength
scale to provide a single electrical output proportional to the photon number.
The basic structure of the PND is the parallel connection of several NbN
superconducting nanowires (100 nm-wide, few nm-thick), folded in a meander
pattern. Electrical and optical equivalents of the device were developed in
order to gain insight on its working principle. PNDs were fabricated on 3-4 nm
thick NbN films grown on sapphire (substrate temperature TS=900C) or MgO
(TS=400C) substrates by reactive magnetron sputtering in an Ar/N2 gas mixture.
The device performance was characterized in terms of speed and sensitivity. The
photoresponse shows a full width at half maximum (FWHM) as low as 660ps. PNDs
showed counting performance at 80 MHz repetition rate. Building the histograms
of the photoresponse peak, no multiplication noise buildup is observable and a
one photon quantum efficiency can be estimated to be QE=3% (at 700 nm
wavelength and 4.2 K temperature). The PND significantly outperforms existing
PNR detectors in terms of simplicity, sensitivity, speed, and multiplication
noise
Сочетанные формы COVID-19 с острыми респираторными вирусными инфекциями у детей
This article presents an observation of 12 patients with combined forms of COVID-19 and acute respiratory viral infections hospitalized at the Z.A. Bashlyaeva State Clinical Hospital, the purpose of which was to identify the features of the course of COVID-19 coronavirus infection in combination with acute respiratory viral infections of various etiologies in children.According to the data obtained, the incidence of COVID-19 and ARVI co-infections was 4.2%. There is a tendency to an increase in the number of patients with lower respiratory tract lesions, a tendency to a prolonged course of COVID-19 with concomitant ARVI, as well as an increase in the duration of hospitalization of patients. В данной статье представлено наблюдение 12 пациентов с сочетанными формами COVID-19 и острыми респираторными вирусными инфекциями, госпитализированных в ГБУЗ ДГКБ им. З.А. Башляевой, целью которого явилось выявление особенностей течения коронавирусной инфекции COVID-19 у детей в сочетании с ОРВИ различной этиологии.Согласно полученным данным, частота встречаемости ко- инфекций COVID-19 и ОРВИ составила 4,2%. Имеется тенденция к росту числа пациентов с поражением нижних дыхательных путей, склонность к затяжному течению COVID-19 при сопутствующих ОРВИ, а также увеличение длительности стационарного лечения.