Quantum Detection of Microwave- and Submillimeter-Wave Radiation Based on Electron Tunneling in Superconductors

A. H. Dayem, Rudolph Martin

E. Burstein, D. N. Langenberg, Barry N. Taylor

Aleksandra A. Gunbina, S. A. Lemzyakov, Michael A. Tarasov +2 more

The response of a detector fabricated on a silicon substrate in the form of a metamaterial that is a 10 × 10 matrix of split rings containing superconductor-insulator-normal metal-insulator-superconductor tunnel structures to submillimeter wave radiation has been experimentally studied. At voltages below the superconducting gap, the electron temperature T e at the substrate temperature T ∼ 0.1 K is ∼0.23 K due to overheating by spurious radiation. At the substrate temperature T ∼ 0.3 K, the electron temperature is close to the substrate temperature T e ≈ T. In both cases, with increasing voltage, T e decreases due to electron cooling and reaches 0.19 K at a voltage corresponding to the maximum response. The response at T = 0.1 K is greater than that at T ∼ 0.3 K by a factor of 5–6. Thus, cooling of only electrons does not provide the same responsivity as cooling of the detector as a whole.

D. N. Langenberg, Douglas J. Scalapino, Barry N. Taylor

The use of Josephson-type superconducting tunnel junctions (two superconductors separated by a very thin insulating layer) as generators of radiation in the range 5 GHz to 1000 GHz is discussed. To this end, the results of recent experiments on the observation of X-band radiation from such junctions are presented, along with a complete discussion of the theory of such junctions. Their potential use as detectors, voltage sources, and harmonic multipliers is also discussed.

Hiroshi Ota, 太田 浩

Faouzi M. Boussaha, Morvan C. Salez, A. Féret +6 more

We report heterodyne measurements of Josephson microwave radiation emitted by a parallel array of small superconductor-insulator-superconductor (SIS) junctions at submillimeter-wave frequencies. The array consists of five Nb/Al–AlOx/Nb junctions nonevenly distributed in a niobium superconducting stripline, and is optimized for rf coupling in the 450–640 GHz range. We observed Fiske-like resonant steps in its I-V curve in the presence of magnetic field. The device was placed in a waveguide mount, and its radiation was quasioptically coupled out of the cryostat, to a SIS-mixer spectrometer in the same frequency range, with a 4–8 GHz band for spectral analysis. We detected a coherent signal in the spectra when the array was biased on the first and third steps, respectively, at the first harmonic frequency of 242 GHz and at the fundamental frequency of 493 GHz, both being the Josephson frequencies associated with their dc voltages. This strongly suggests that this type of parallel arrays optimized for wideband rf coupling, though strongly discretized, hosts dynamic fluxon regimes similar to long Josephson junctions, which could find applications in superconducting digital electronics or integrated heterodyne submillimeter-wave receivers.