Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

IEEE Transactions on Magnetics

Response of Nb-aSi-Nb junctions to 604 GHz radiation

W. C. Danchi, John U. Free, F. Habbal, M. Tinkham, L. N. Smith

Published Mar 1, 1985• 3 citations
Publisher

Abstract

We have measured the response of Nb-aSi-Nb junctions to 604 GHz radiation from an optically pumped far-infrared (FIR) laser source. These rugged and thermally cyclable junctions situated at the midpoint of 180 μm long dipole antennas, were fabricated on oxidized silicon wafers using the Selective Niobium Anodization Process (SNAP). Josephson current densities were\sim 9,000A/cm2, the McCumber parameters βcwere ∼3.5, and the Josephson plasma frequencies\omega_{J}\sim2.5\times10^{12}. On a junction with a normal state resistance of\sim7\Omega, we observed three Josephson steps and one photon-assisted tunneling step. The widths of the Josephson steps were studied as a function of the laser power. An RSJ model computer simulation with a nonlinear quasiparticle conductance and an rf current bias (assumed because of the low junction resistance) is able to account reasonably well for the laser-power dependence of the critical current (zeroth step) and the second step. However, the temperature dependence is more complex, and a discrepancy still exists between the RSJ model calculation and the data for the hysteretic first step.

DOI
10.1109/tmag.1985.1063816

Related papers

Photon-assisted tunneling and AC Josephson effect at 246 and 604 GHz in small-area superconducting tunnel junctions

W. C. Danchi, F. Habbal, M. Tinkham

We report the first observations of photon-assisted quasiparticle tunneling and AC Josephson effect in superconducting tunnel junctions irradiated with far-infrared (FIR) radiation. Radiation at 246 GHz (λ=1.22 mm) and 604 GHz (496 μm) from an optically-pumped FIR laser source was used. Tin-tin oxide-lead junctions of ∼1 (μm)2area were fabricated on crystal quartz substrates with integral planar dipole antennas of resonant length at the frequency of the incident radiation. The observed photon-assisted tunneling features are in excellent agreement with the Tien-Gordon theory, and the inferred responsivity approaches the quantum limit at low temperatures for photon energies less than the gap. At 604 GHz, with a 176 ohm junction, we have seen 7 Josephson steps, comparable to point contact performance. The variation of the step widths with laser power is found to agree quite well with both the RSJ model and the Werthamer theory. For low resistance junctions (e.g. 16 ohms), we find the Josephson steps to be flat and to agree well with the shape predicted by the RSJ model without noise rounding, while noise rounding is very evident with the higher resistance junctions. In all cases, the step shape is in reasonable agreement with the theory of P. A. Lee, using a noise temperature of 10-20K with an appropriate small junction capacitance.

IEEE Transactions on Magnetics•May 1, 1983•3 citations

Terahertz Shapiro steps in high temperature SNS Josephson junctions

Peter A. Rosenthal, Erich N. Grossman

We have studied the far infrared behavior of high -T/sub c/ superconductor-normal metal-superconductor (SNS) microbridges with T/sub c/>85 K and critical current-resistance products (I/sub c/R/sub N/) as high as 10 mV at 4 K. These are the highest I/sub c/R/sub N/ products reported to date for microfabricated Josephson junctions of any material. The junctions were integrated at the feeds of planar log-periodic antennas made from Au thin films. The junctions had dc normal state resistances R/sub N/ between 6 and 38 /spl Omega/, reasonably well matched to the antenna's estimated RF impedance of 53 /spl Omega/. Far infrared laser radiation at 404, 760, and 992 GHz induced distinct Shapiro steps (i.e. constant voltage steps at voltages n(hf/2e), n=1,2,...) in the current voltage characteristics as well as modulation of the critical current. Steps were observed at voltages up to 17 mV and 6 mV, at temperatures of 9 K and 57 K respectively. This corresponds to maximum Josephson oscillation frequencies of 8 and 3 THz at these temperatures. These are the first far infrared measurements performed on high T/sub c/ junctions. Measurements of the power, frequency, and temperature dependence of the Shapiro steps are presented and discussed in the context of a resistively and capacitively shunted junction (RCSJ) model. A value of 4.5 fF for the junction capacitance is inferred from the hysteresis of the slightly underdamped current-voltage characteristics.>

IEEE Transactions on Microwave Theory and Techniques•Apr 1, 1994•47 citations

Terahertz Shapiro Steps in High Temperature SNS Josephson Junctions

Peter A. Rosenthal, Erich N. Grossman

We have studied the far infrared behavior of high -T/sub c/ superconductor-normal metal-superconductor (SNS) microbridges with T/sub c/>85 K and critical current-resistance products (I/sub c/R/sub N/) as high as 10 mV at 4 K. These are the highest I/sub c/R/sub N/ products reported to date for microfabricated Josephson junctions of any material. The junctions were integrated at the feeds of planar log-periodic antennas made from Au thin films. The junctions had dc normal state resistances R/sub N/ between 6 and 38 /spl Omega/, reasonably well matched to the antenna's estimated RF impedance of 53 /spl Omega/. Far infrared laser radiation at 404, 760, and 992 GHz induced distinct Shapiro steps (i.e. constant voltage steps at voltages n(hf/2e), n=1,2,...) in the current voltage characteristics as well as modulation of the critical current. Steps were observed at voltages up to 17 mV and 6 mV, at temperatures of 9 K and 57 K respectively. This corresponds to maximum Josephson oscillation frequencies of 8 and 3 THz at these temperatures. These are the first far infrared measurements performed on high T/sub c/ junctions. Measurements of the power, frequency, and temperature dependence of the Shapiro steps are presented and discussed in the context of a resistively and capacitively shunted junction (RCSJ) model. A value of 4.5 fF for the junction capacitance is inferred from the hysteresis of the slightly underdamped current-voltage characteristics. >

Softwaretechnik-Trends•Apr 1, 1993•0 citations

Point-contact-type Josephson harmonic mixer for frequency measurement of far-infrared lasers

Yukinobu Miki, Eiichi Sakuma, Masanao Morimura

Point-contact-type Josephson junctions have been developed as a harmonic mixer to measure far-infrared (FIR) laser frequencies in a frequency chain up to the infrared region. The junctions were formed by mechanically pressing a niobium wire of 70 μm in diameter with a sharply etched tip against a niobium post of 2 mm in diameter. The voltage-current characteristics of the mixers were investigated under the irradiation of FIR lights from an optically pumped methyl-alcohol laser. The Shapiro steps for FIR lights up to 3.1 THz were observed. The mixing properties of the mixers were studied through harmonic mixing experiments of 50-GHz microwaves and the FIR lights up to the frequency of 3.1 THz. The conversion efficiency of the beat signals to the incident FIR power was found to vary as the — 4th power of the FIR frequency. From the mixing properties, the combination of the critical current Icof the junction and the product IcRnwhere Rnis the normal resistance of the junction, was found important to optimize the mixing performance.

IEEE Transactions on Instrumentation and Measurement•Jun 1, 1987•3 citations

Direct detection at FIR frequencies with niobium tunnel junctions

J. Prince, Bascom S. Deaver, S. Withington

Measurements have been made on an array of six niobium/aluminum-aluminum oxide/niobium junctions with an integrated bow-tie antenna at 584 GHz. These measurements include examining the response of current-voltage curves at different incident radiation powers, both with and without an applied magnetic field. The measurements also include the responsivity and the noise of the devices as direct detectors. A planar superconducting quantum interference device (SQUID) was used as the low-frequency amplifier, and a chopped far infrared (FIR) laser generated the radiation. Comparisons with theoretical predictions show good fits to the current-voltage curves, except at the highest powers where there is evidence of heating and possibly nonequilibrium processes. Current responsivities of greater than one-half of the quantum limit and a noise equivalent power of 2*10/sup 1-4/ W/ square root Hz have been obtained.>

IEEE Transactions on Applied Superconductivity•Mar 1, 1993•1 citation

FIR response of intrinsic Josephson junctions

S. Rother, Yuri Koval, Paul Müller +4 more

We present experiments on the far infrared response of intrinsic Josephson junctions in Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+x/ (BSCCO). We detected first order Shapiro steps on resistive branches in a frequency range between 584 GHz and 2.5 THz. Due to the very low power coupled into the junctions the suppression of the critical current was only weak. With increasing number of junctions in the resistive state a higher amplitude of the Shapiro steps was measured. As the frequencies are well above the plasma frequency of our junctions, the steps are expected to be stable at any power level. To verify this, step heights were studied at various power levels as a function of frequency. The impedance matching of the system improved considerably when several junctions have switched into the resistive state.

IEEE Transactions on Applied Superconductivity•Mar 1, 2001•12 citations
We have measured the response of Nb-aSi-Nb junctions to 604 GHz radiation from an optically pumped far-infrared (FIR) laser source. These rugged and thermally cyclable junctions situated at the midpoint of 180 μm long dipole antennas, were fabricated on oxidized silicon wafers using the Selective Niobium Anodization Process (SNAP). Josephson current densities were\sim 9,000A/cm2, the McCumber parameters βcwere ∼3.5, and the Josephson plasma frequencies\omega_{J}\sim2.5\times10^{12}. On a junction with a normal state resistance of\sim7\Omega, we observed three Josephson steps and one photon-assisted tunneling step. The widths of the Josephson steps were studied as a function of the laser power. An RSJ model computer simulation with a nonlinear quasiparticle conductance and an rf current bias (assumed because of the low junction resistance) is able to account reasonably well for the laser-power dependence of the critical current (zeroth step) and the second step. However, the temperature dependence is more complex, and a discrepancy still exists between the RSJ model calculation and the data for the hysteretic first step.
We report the first observations of photon-assisted quasiparticle tunneling and AC Josephson effect in superconducting tunnel junctions irradiated with far-infrared (FIR) radiation. Radiation at 246 GHz (λ=1.22 mm) and 604 GHz (496 μm) from an optically-pumped FIR laser source was used. Tin-tin oxide-lead junctions of ∼1 (μm)2area were fabricated on crystal quartz substrates with integral planar dipole antennas of resonant length at the frequency of the incident radiation. The observed photon-assisted tunneling features are in excellent agreement with the Tien-Gordon theory, and the inferred responsivity approaches the quantum limit at low temperatures for photon energies less than the gap. At 604 GHz, with a 176 ohm junction, we have seen 7 Josephson steps, comparable to point contact performance. The variation of the step widths with laser power is found to agree quite well with both the RSJ model and the Werthamer theory. For low resistance junctions (e.g. 16 ohms), we find the Josephson steps to be flat and to agree well with the shape predicted by the RSJ model without noise rounding, while noise rounding is very evident with the higher resistance junctions. In all cases, the step shape is in reasonable agreement with the theory of P. A. Lee, using a noise temperature of 10-20K with an appropriate small junction capacitance.
We have studied the far infrared behavior of high -T/sub c/ superconductor-normal metal-superconductor (SNS) microbridges with T/sub c/>85 K and critical current-resistance products (I/sub c/R/sub N/) as high as 10 mV at 4 K. These are the highest I/sub c/R/sub N/ products reported to date for microfabricated Josephson junctions of any material. The junctions were integrated at the feeds of planar log-periodic antennas made from Au thin films. The junctions had dc normal state resistances R/sub N/ between 6 and 38 /spl Omega/, reasonably well matched to the antenna's estimated RF impedance of 53 /spl Omega/. Far infrared laser radiation at 404, 760, and 992 GHz induced distinct Shapiro steps (i.e. constant voltage steps at voltages n(hf/2e), n=1,2,...) in the current voltage characteristics as well as modulation of the critical current. Steps were observed at voltages up to 17 mV and 6 mV, at temperatures of 9 K and 57 K respectively. This corresponds to maximum Josephson oscillation frequencies of 8 and 3 THz at these temperatures. These are the first far infrared measurements performed on high T/sub c/ junctions. Measurements of the power, frequency, and temperature dependence of the Shapiro steps are presented and discussed in the context of a resistively and capacitively shunted junction (RCSJ) model. A value of 4.5 fF for the junction capacitance is inferred from the hysteresis of the slightly underdamped current-voltage characteristics.>
We have studied the far infrared behavior of high -T/sub c/ superconductor-normal metal-superconductor (SNS) microbridges with T/sub c/>85 K and critical current-resistance products (I/sub c/R/sub N/) as high as 10 mV at 4 K. These are the highest I/sub c/R/sub N/ products reported to date for microfabricated Josephson junctions of any material. The junctions were integrated at the feeds of planar log-periodic antennas made from Au thin films. The junctions had dc normal state resistances R/sub N/ between 6 and 38 /spl Omega/, reasonably well matched to the antenna's estimated RF impedance of 53 /spl Omega/. Far infrared laser radiation at 404, 760, and 992 GHz induced distinct Shapiro steps (i.e. constant voltage steps at voltages n(hf/2e), n=1,2,...) in the current voltage characteristics as well as modulation of the critical current. Steps were observed at voltages up to 17 mV and 6 mV, at temperatures of 9 K and 57 K respectively. This corresponds to maximum Josephson oscillation frequencies of 8 and 3 THz at these temperatures. These are the first far infrared measurements performed on high T/sub c/ junctions. Measurements of the power, frequency, and temperature dependence of the Shapiro steps are presented and discussed in the context of a resistively and capacitively shunted junction (RCSJ) model. A value of 4.5 fF for the junction capacitance is inferred from the hysteresis of the slightly underdamped current-voltage characteristics. >
Point-contact-type Josephson junctions have been developed as a harmonic mixer to measure far-infrared (FIR) laser frequencies in a frequency chain up to the infrared region. The junctions were formed by mechanically pressing a niobium wire of 70 μm in diameter with a sharply etched tip against a niobium post of 2 mm in diameter. The voltage-current characteristics of the mixers were investigated under the irradiation of FIR lights from an optically pumped methyl-alcohol laser. The Shapiro steps for FIR lights up to 3.1 THz were observed. The mixing properties of the mixers were studied through harmonic mixing experiments of 50-GHz microwaves and the FIR lights up to the frequency of 3.1 THz. The conversion efficiency of the beat signals to the incident FIR power was found to vary as the — 4th power of the FIR frequency. From the mixing properties, the combination of the critical current Icof the junction and the product IcRnwhere Rnis the normal resistance of the junction, was found important to optimize the mixing performance.
Measurements have been made on an array of six niobium/aluminum-aluminum oxide/niobium junctions with an integrated bow-tie antenna at 584 GHz. These measurements include examining the response of current-voltage curves at different incident radiation powers, both with and without an applied magnetic field. The measurements also include the responsivity and the noise of the devices as direct detectors. A planar superconducting quantum interference device (SQUID) was used as the low-frequency amplifier, and a chopped far infrared (FIR) laser generated the radiation. Comparisons with theoretical predictions show good fits to the current-voltage curves, except at the highest powers where there is evidence of heating and possibly nonequilibrium processes. Current responsivities of greater than one-half of the quantum limit and a noise equivalent power of 2*10/sup 1-4/ W/ square root Hz have been obtained.>
We present experiments on the far infrared response of intrinsic Josephson junctions in Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+x/ (BSCCO). We detected first order Shapiro steps on resistive branches in a frequency range between 584 GHz and 2.5 THz. Due to the very low power coupled into the junctions the suppression of the critical current was only weak. With increasing number of junctions in the resistive state a higher amplitude of the Shapiro steps was measured. As the frequencies are well above the plasma frequency of our junctions, the steps are expected to be stable at any power level. To verify this, step heights were studied at various power levels as a function of frequency. The impedance matching of the system improved considerably when several junctions have switched into the resistive state.