We propose a mesoscopic kinetic-inductance radiation detector based on a long superconductor-normal metal-superconductor Josephson junction. The operation of this proximity Josephson sensor relies on large kinetic inductance variations under irradiation due to the exponential temperature dependence of the critical current. Coupled with a dc superconducting quantum interference device readout, the PJS is able to provide a signal to noise (S/N) ratio up to ∼103 in the terahertz regime if operated as calorimeter, while electrical noise equivalent power as low as ∼7×10−20W∕Hz at 200mK can be achieved in the bolometer operation. The high performance together with the ease of fabrication make this structure attractive as an ultrasensitive cryogenic detector of terahertz electromagnetic radiation.
We propose a mesoscopic kinetic-inductance radiation detector based on a long superconductor-normal metal-superconductor Josephson junction. The operation of this proximity Josephson sensor relies on large kinetic inductance variations under irradiation due to the exponential temperature dependence of the critical current. Coupled with a dc superconducting quantum interference device readout, the PJS is able to provide a signal to noise (S/N) ratio up to ∼103 in the terahertz regime if operated as calorimeter, while electrical noise equivalent power as low as ∼7×10−20W∕Hz at 200mK can be achieved in the bolometer operation. The high performance together with the ease of fabrication make this structure attractive as an ultrasensitive cryogenic detector of terahertz electromagnetic radiation.
While experimental studies of kinetic-inductance sensors have been limited so far by the temperature range near the superconducting transition, these detectors can be very sensitive at temperatures well below the transition, where the number of equilibrium quasiparticles is exponentially small. In this regime, a shift of the quasiparticle chemical potential under radiation results in the change of the kinetic inductance, which can be measured by a sensitive SQUID readout. We modeled the kinetic inductance response of detectors made from disordered superconducting Nb, NbC, and MoRe films. Low phonon transparency of the interface between the superconductor and the substrate causes substantial re-trapping of phonons providing high quantum efficiency and the operating time of ∼1 ms at ≈1 K. Due to the small number of quasiparticles, the noise equivalent power of the detector determined by the quasiparticle generation-recombination noise can be as small as ∼10−19 W/√Hz at He4 temperatures.
While most experimental studies of kinetic-inductance sensors have been limited so far by the temperature range near the superconducting transition, kinetic-inductance detectors can be very sensitive at temperatures well below the transition, where the number of equilibrium quasiparticles is exponentially small. In this regime, a shift of the quasiparticle chemical potential under radiation results in the change of the kinetic inductance. We modeled the noise characteristics of the kinetic-inductance detectors made from disordered superconducting Nb, NbC, and MoRe films. Low-phonon transparency of the interface between the superconductor and the substrate causes substantial retrapping of phonons providing high quantum efficiency and the operating time of ∼1 ms at ≈1 K. Due to the small number of quasiparticles, the noise equivalent power of the detector determined by the quasiparticle generation–recombination noise can be as small as ∼10−19 W/Hz at He4 temperatures.
The concept of nonlinear kinetic inductance sensor (NKIS) of electromagnetic radiation is proposed. The idea is based on divergency of kinetic inductance Lk∼dq/dI ( ℏq is a momentum of superconducting electrons, I is a supercurrent) of hybrid superconductor/normal metal (SN) bridge at current I*<Idep ( Idep is a depairing current of the hybrid) and temperature T* much smaller than critical temperature Tc . It makes possible to have large change of phase difference δϕ along SN bridge in current biased regime at I≃I* even for small electron temperature increase. Appearance of δϕ is accompanied by the change of the current and magnetic flux through the coupled superconducting ring which could be measured with help of superconducting quantum interference device (SQUID). In some respect proposed sensor may be considered as a superconducting counterpart of transition edge sensor (TES) those work is based on large derivative dR/dT ( R is a resistance) near Tc . Because at I≃I* SN bridge is in gapless regime there is no low boundary for frequency of detected electromagnetic radiation. Our calculations show that such a sensor can operate in single photon regime and detect single photons with frequency ν≳ 10 GHz. We argue that the nontrivial dependence I(q) of SN bridge could be also used in detectors of continuous electromagnetic radiation, current and magnetic field sensors.
For sensitive wideband spectroscopy at THz frequencies with performance better than for Fourier Transform Spectrometer, one needs a wide-range electrically tunable, narrow linewidth THz source, and a sensitive broadband detector. To obtain a low noise level of sensor we use a superconducting normal metal cold electron bolometer (CEB). A voltage response of the bolometer is 4.108 V/W and an amplifier-limited technical noise equivalent power of the bolometer is 1.25.10-17 W/Hz1/2. The wide band electrically tuned terahertz band cryogenic oscillator is a Josephson junction. Contrary to conventional Josephson junctions based on niobium, and naturally limited in frequency by energy gap of about 700 GHz, the high critical temperature YBaCuO junctions can extend this limit by an order of magnitude. At 4 K such oscillators can radiate at frequencies exceeding 2 THz. Signals received by bolometers integrated with double-dipole and log-periodic antennas and irradiated by the Josephson oscillator show in our experiments the high frequency response corresponding to an oscillation frequency of up to 1.75 THz. Such cryogenic terahertz network analyzer is suitable for low-signal spectral evaluation of cryogenic detectors, quasioptical sub-mm cryogenic filters, planar antennas with planar microwave filters, integrated structures comprising such elements, and arrays of cryogenic receivers.
Abstract Single-photon detectors based on the superconducting transition-edge sensor are used in a number of visible to near-infrared applications, particularly for photon-number-resolving measurements in quantum information science. To be practical for large-scale spectroscopic imaging or photonic quantum computing applications, the size of visible to near-infrared transition-edge sensor arrays and their associated readouts must be increased from a few pixels to many thousands. In this manuscript, we introduce the kinetic inductance current sensor, a scalable readout technology that exploits the nonlinear kinetic inductance in a superconducting resonator to make sensitive current measurements. Kinetic inductance current sensors can replace superconducting quantum interference devices for many applications because of their ability to measure fast, high slew-rate signals, their compatibility with standard microwave frequency-division multiplexing techniques, and their relatively simple fabrication. Here, we demonstrate the readout of a visible to near-infrared transition-edge sensor using a kinetic inductance current sensor with 3.7 MHz of bandwidth. We measure a readout noise of 1.4pA/Hz 1.4 pA / Hz , considerably below the detector noise at frequencies of interest, and an energy resolution of (0.137 ± 0.001) eV at 0.8 eV, comparable to resolutions observed with non-multiplexed superconducting quantum interference device readouts.
Abstract We have designed and fabricated a superconducting hybrid NbTiN-Al kinetic inductance detector (KID) over a broad band centered at 4.3 THz. The detector sensitivity is characterized by changing the bath temperature in a dark environment. Both amplitude and phase readouts are performed. The measured electrical noise equivalent power for phase readout is about 2.6 × 10−18 W · Hz−0.5 at 200 mK. This ultra-sensitive KID, which enables large arrays with frequency domain multiplexing, is promising for imaging instruments in space-based far-infrared observatories.