Capacitively coupled hot-electron nanobolometer as far-infrared photon counter

We show theoretically that hot-electron nanobolometers consisting of a small piece of normal metal, capacitively coupled to a superconducting antenna through a pair of normal metal--insulator--superconductor (NIS) tunnel junctions may be used as far-infrared photon counters. To make the device most effective at high counting rates, we suggest the use of the bolometer in the simplest configuration, when the NIS tunnel junctions are used as both an electron cooler and thermometer. The absorption of the photon in the normal metal produces a pulse in the electron temperature, which is measured by the NIS junctions. The counter may resolve photons up to 0.3--0.4 mm wavelength and has a typical re-equilibration time constant of about 20 ns.Comment: 4 pages with 2 figure

A Parallel/Series Array of Cold-Electron Bolometers with SIN Tunnel Junctions for Cosmology Experiments

A novel concept of the parallel/series array of Cold-Electron Bolometers (CEB) with Superconductor-Insulator-Normal (SIN) Tunnel Junctions has been proposed for matching with JFET readout. The current-biased CEBs are connected in series for DC and in parallel for HF signal. A signal is concentrated to the absorber through the capacitance of tunnel junctions and additional capacitance for coupling of superconducting islands. Due to dividing power between CEBs in the array and increasing responsivity, the noise matching could be effectively optimized and the photon Noise Equivalent Power could be easily achieved at 300 mK with a room temperature JFET readout

Ultimate Cold-Electron Bolometer with Strong Electrothermal Feedback

A novel concept of the Cold-Electron Bolometer (CEB) with strong electrothermal feedback has been proposed. The concept is based on direct electron cooling of the absorber that serves as negative electrothermal feedback for incoming signal. This feedback is analogous to TES (transition-edge sensor) but additional dc heating is replaced by deep electron cooling to minimum temperature. It could mean a principle breakthrough in realization of supersensitive detectors. Noise properties are considerably improved by decreasing the electron temperature. The loop gain of electrothermal feedback could exceed 1000. The response time is reduced by electrothermal feedback to 10ns in comparison with the intrinsic e-ph time constant of 10µs. The CEB gives opportunity to increase dynamic range by removing all incoming power from supersensitive absorber to the next stage of readout system (SQUID) with higher dynamic range. Saturation problems are not so severe for CEB as for TES: after exceeding the cooling power there is only slight deviation from linear dependence for voltage response. The full saturation comes at the level of 100pW when temperature of absorber achieves Tc of Al. Ultimate performance of the CEB is determined by shot noise of the signal readout. For relatively low background load P0 =10fW and quantization level Te= 50mK, the limit NEP is equal to 10--19W/Hz1/2. The estimations show that it is realistic to achieve ultimate NEP at 100 mK with SQUID readout system and NEP=10—18W/Hz1/2 at 300mK for background load of 10fW. Applicability of the CEB to post-Herschel missions looks very promising

Concept of a mixer based on a cold-electron bolometer

A phase-sensitive terahertz heterodyne mixer of a new type based on a cold-electron bolometer is proposed. In this mixer, a normal-metal thin-film absorber is connected to a planar antenna via superconductor-insulator-normal metal (SIN) tunnel junctions, thus forming a SINIS structure. The SINIS mixer combines the advantages of a hot-electron bolometer (HEB), such as a high signal frequency at a small local oscillator power, with the advantages of an SIS mixer, including low noise level, a high intermediate frequency, and wide working temperature range (up to a critical temperature of the superconductor). In contrast to the HEB and SIS mixers, the proposed device is less sensitive to external magnetic noise and exhibits no additional noise related to the superconducting transition and the Josephson effect

Theory of a large thermoeffect in superconductors doped with magnetic impurities

We argue that parametrically strong enhancement of a thermoelectric current can be observed in conventional superconductors doped by magnetic impurities. This effect is caused by violation of the symmetry between electron-like and hole-like excitations due to formation of subgap Andreev bound states in the vicinity of magnetic impurities. We develop a quantitative theory of this effect and demonstrate that it can be detected in modern experiments.Comment: 5 pages, 4 figure

A broadband detector based on series YBCO grain boundary Josephson junctions

Modeling of a broadband receiving system based on a meander series of Josephson YBaCuO grain boundary junctions integrated into a log-periodic antenna was carried out. The electromagnetic properties of the system, namely amplitude-frequency characteristic, beam pattern, and fraction of the absorbed power in each Josephson junction were investigated. Based on the obtained results, a numerical simulation of one-dimensional arrays was carried out. The dc characteristics of the detector were calculated, that is, current-voltage characteristic, responsivity, noise, and noise-equivalent power (NEP) for a 250 GHz external signal. The optimal number of junctions to obtain the minimum NEP was found. The use of a series of junctions allows one to increase the responsivity by a factor of 2.5, the NEP value by a factor of 1.5, and the power dynamic range by a factor of 5. For typical YBaCuO Josephson junctions fabricated on a ZrYO bicrystal substrate by magnetron deposition, the following parameters were obtained at a temperature of 77 K: responsivity = 9 kV/W; NEP = 3.10(-13) W/Hz((1/2)); power dynamic range = 1.10(6)

Multichroic Bandpass Seashell Antenna with Cold-Electron Bolometers for CMB Measurements

A novel type of the multichroic "seashell" resonant antenna is developed for CMB measurements. The polarized slot antennas are arranged in the compact form of a seashell with individual slots for each frequency and each polarization. Such an arrangement gives unique opportunity for independent adjusting individual parameters of slots with microstrip lines (MSL) and bolometers. For each frequency band the seashell antenna contains two pairs of orthogonal slots for each polarization connected by microstrip lines (MSL) with a bolometer in the middle for in-phase operation. To fit slots in lambda/2 area for the best beam shape, lumped capacitances in the form of H-slot were introduced. Ellipticity of a beam was improved to the level of better than 1%. The seashell antenna gives a unique opportunity to select needed bandwidth by resonant properties of slots themselves. Slots are phased by MSLs connecting two opposite slots with a resistive Cold-Electron Bolometer (CEB) placed just in middle of two MSLs. MSLs and CEBs are placed just in the area of the seashell antenna. The resonant seashell antenna with CEBs avoids long MSLs bringing signal outside the antenna to large external filters as in the case of sinuous antenna. This innovation avoids losses in long MSLs and increases frequency range

Responsivity and noise equivalent power of a single cold-electron bolometer

We have developed a single-pixel capacitively coupled Cold-Electron Bolometer (CEB) and characterized it in the current-biased regime. The most attractive feature of the CEB is effective electron self-cooling of the absorber, which leads to a lower bolometer noise and higher dynamic range. The bolometer responsivity was measured by determining the voltage response to an applied power through the absorber from a heating current, modulated at frequencies from 35 Hz to 2 kHz. The optimum responsivity of 1.5 7 10 V/W was measured at a modulation frequency of 35 Hz. The noise equivalent power (NEP) was subsequently obtained from the estimated bolometer noise voltage with respect to the measured bolometer responsivity. The NEP of better 2 7 10 W/Hz was obtained for modulation frequencies greater than 100 Hz. The background power and the bolometer time constant were also estimated from the experimental results. The photon-noise-limited operation of CEB will dominate for a signal power of 10 fW and higher at frequency 80 GHz and higher. 10 −18 1/