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A Josephson radiation comb generator.

Solinas P, Gasparinetti S, Golubev D, Giazotto F - Sci Rep (2015)

Bottom Line: In the frequency domain, this corresponds to a comb-like structure similar to the one exploited in optics and metrology.With this device it is possible to generate up to several hundreds of harmonics of the driving frequency.For example, a chain of 50 identical high-critical-temperature SQUIDs driven at 1 GHz can deliver up to a 0.5 nW at 200 GHz.

View Article: PubMed Central - PubMed

Affiliation: SPIN-CNR, Via Dodecaneso 33, 16146 Genova, Italy.

ABSTRACT
We propose the implementation of a Josephson Radiation Comb Generator (JRCG) based on a dc superconducting quantum interference device (SQUID) driven by an external magnetic field. When the magnetic flux crosses a diffraction node of the critical current interference pattern, the superconducting phase undergoes a jump of π and a voltage pulse is generated at the extremes of the SQUID. Under periodic drive this allows one to generate a sequence of sharp, evenly spaced voltage pulses. In the frequency domain, this corresponds to a comb-like structure similar to the one exploited in optics and metrology. With this device it is possible to generate up to several hundreds of harmonics of the driving frequency. For example, a chain of 50 identical high-critical-temperature SQUIDs driven at 1 GHz can deliver up to a 0.5 nW at 200 GHz. The availability of a fully solid-state radiation comb generator such as the JRCG, easily integrable on chip, may pave the way to a number of technological applications, from metrology to sub-millimeter wave generation.

No MeSH data available.


The Josephson radiation comb generator.(a) A current-biased, flux driven SQUID generates a time-dependent voltage V(t). The SQUID consists of two superconducting electrodes S (green) connected by two Josephson junctions (red). φi is the phase across the i-th junction, IB is the constant current bias and Φ(t) is the time-dependent magnetic flux. (b) Normalized critical current Ic(ϕ)/I+ versus normalized magnetic flux ϕ = πΦ/Φ0 for a symmetric SQUID (solid line). The ϕ-dependent term cos ϕ is also plotted as a dashed line. The phase φ across the SQUID undergoes a π jump whenever ϕ crosses an interference node, due to the change in sign of cos ϕ. Phase jumps can be induced by modulating the flux in time around an interference node with a small amplitude ε (red line). (c) RCSJ model circuit for the SQUID, with resistance R, Josephson inductance LJ, and capacitance C. (d) Time-dependent tilted-washboard potential for the RCSJ model. The potential is plotted at the initial time (t0 = 0), at an intermediate time (t1 = 0.17/ν, where ν is the frequency of the modulation), and just after the vanishing of the potential barrier (t2 = 0.26/ν). The phase particle (purple ball) starts in an energetic minimum at φ = 2kπ. At times later than 1/(4ν), the position of the particle becomes unstable, leading to a phase jump to the nearest minimum at φ = (2k + 1)π. The direction of the jump is determined by the washboard tilt δ = IB/I+, with δ ≪ 1.
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f1: The Josephson radiation comb generator.(a) A current-biased, flux driven SQUID generates a time-dependent voltage V(t). The SQUID consists of two superconducting electrodes S (green) connected by two Josephson junctions (red). φi is the phase across the i-th junction, IB is the constant current bias and Φ(t) is the time-dependent magnetic flux. (b) Normalized critical current Ic(ϕ)/I+ versus normalized magnetic flux ϕ = πΦ/Φ0 for a symmetric SQUID (solid line). The ϕ-dependent term cos ϕ is also plotted as a dashed line. The phase φ across the SQUID undergoes a π jump whenever ϕ crosses an interference node, due to the change in sign of cos ϕ. Phase jumps can be induced by modulating the flux in time around an interference node with a small amplitude ε (red line). (c) RCSJ model circuit for the SQUID, with resistance R, Josephson inductance LJ, and capacitance C. (d) Time-dependent tilted-washboard potential for the RCSJ model. The potential is plotted at the initial time (t0 = 0), at an intermediate time (t1 = 0.17/ν, where ν is the frequency of the modulation), and just after the vanishing of the potential barrier (t2 = 0.26/ν). The phase particle (purple ball) starts in an energetic minimum at φ = 2kπ. At times later than 1/(4ν), the position of the particle becomes unstable, leading to a phase jump to the nearest minimum at φ = (2k + 1)π. The direction of the jump is determined by the washboard tilt δ = IB/I+, with δ ≪ 1.

Mentions: Our proposal for a JRCG is based on a dc SQUID (see Fig. 1a), consisting of two Josephson junctions arranged in parallel in a superconducting loop. The SQUID is biased by a constant current IB and it is driven by an external, time-dependent magnetic flux Φ. Here we assume the inductance of the loop to be negligible with respect to the Josephson inductance of the junctions. Due to the first Josephson relation6, the current (IJ) vs phase relation of the SQUID reads


A Josephson radiation comb generator.

Solinas P, Gasparinetti S, Golubev D, Giazotto F - Sci Rep (2015)

The Josephson radiation comb generator.(a) A current-biased, flux driven SQUID generates a time-dependent voltage V(t). The SQUID consists of two superconducting electrodes S (green) connected by two Josephson junctions (red). φi is the phase across the i-th junction, IB is the constant current bias and Φ(t) is the time-dependent magnetic flux. (b) Normalized critical current Ic(ϕ)/I+ versus normalized magnetic flux ϕ = πΦ/Φ0 for a symmetric SQUID (solid line). The ϕ-dependent term cos ϕ is also plotted as a dashed line. The phase φ across the SQUID undergoes a π jump whenever ϕ crosses an interference node, due to the change in sign of cos ϕ. Phase jumps can be induced by modulating the flux in time around an interference node with a small amplitude ε (red line). (c) RCSJ model circuit for the SQUID, with resistance R, Josephson inductance LJ, and capacitance C. (d) Time-dependent tilted-washboard potential for the RCSJ model. The potential is plotted at the initial time (t0 = 0), at an intermediate time (t1 = 0.17/ν, where ν is the frequency of the modulation), and just after the vanishing of the potential barrier (t2 = 0.26/ν). The phase particle (purple ball) starts in an energetic minimum at φ = 2kπ. At times later than 1/(4ν), the position of the particle becomes unstable, leading to a phase jump to the nearest minimum at φ = (2k + 1)π. The direction of the jump is determined by the washboard tilt δ = IB/I+, with δ ≪ 1.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4507479&req=5

f1: The Josephson radiation comb generator.(a) A current-biased, flux driven SQUID generates a time-dependent voltage V(t). The SQUID consists of two superconducting electrodes S (green) connected by two Josephson junctions (red). φi is the phase across the i-th junction, IB is the constant current bias and Φ(t) is the time-dependent magnetic flux. (b) Normalized critical current Ic(ϕ)/I+ versus normalized magnetic flux ϕ = πΦ/Φ0 for a symmetric SQUID (solid line). The ϕ-dependent term cos ϕ is also plotted as a dashed line. The phase φ across the SQUID undergoes a π jump whenever ϕ crosses an interference node, due to the change in sign of cos ϕ. Phase jumps can be induced by modulating the flux in time around an interference node with a small amplitude ε (red line). (c) RCSJ model circuit for the SQUID, with resistance R, Josephson inductance LJ, and capacitance C. (d) Time-dependent tilted-washboard potential for the RCSJ model. The potential is plotted at the initial time (t0 = 0), at an intermediate time (t1 = 0.17/ν, where ν is the frequency of the modulation), and just after the vanishing of the potential barrier (t2 = 0.26/ν). The phase particle (purple ball) starts in an energetic minimum at φ = 2kπ. At times later than 1/(4ν), the position of the particle becomes unstable, leading to a phase jump to the nearest minimum at φ = (2k + 1)π. The direction of the jump is determined by the washboard tilt δ = IB/I+, with δ ≪ 1.
Mentions: Our proposal for a JRCG is based on a dc SQUID (see Fig. 1a), consisting of two Josephson junctions arranged in parallel in a superconducting loop. The SQUID is biased by a constant current IB and it is driven by an external, time-dependent magnetic flux Φ. Here we assume the inductance of the loop to be negligible with respect to the Josephson inductance of the junctions. Due to the first Josephson relation6, the current (IJ) vs phase relation of the SQUID reads

Bottom Line: In the frequency domain, this corresponds to a comb-like structure similar to the one exploited in optics and metrology.With this device it is possible to generate up to several hundreds of harmonics of the driving frequency.For example, a chain of 50 identical high-critical-temperature SQUIDs driven at 1 GHz can deliver up to a 0.5 nW at 200 GHz.

View Article: PubMed Central - PubMed

Affiliation: SPIN-CNR, Via Dodecaneso 33, 16146 Genova, Italy.

ABSTRACT
We propose the implementation of a Josephson Radiation Comb Generator (JRCG) based on a dc superconducting quantum interference device (SQUID) driven by an external magnetic field. When the magnetic flux crosses a diffraction node of the critical current interference pattern, the superconducting phase undergoes a jump of π and a voltage pulse is generated at the extremes of the SQUID. Under periodic drive this allows one to generate a sequence of sharp, evenly spaced voltage pulses. In the frequency domain, this corresponds to a comb-like structure similar to the one exploited in optics and metrology. With this device it is possible to generate up to several hundreds of harmonics of the driving frequency. For example, a chain of 50 identical high-critical-temperature SQUIDs driven at 1 GHz can deliver up to a 0.5 nW at 200 GHz. The availability of a fully solid-state radiation comb generator such as the JRCG, easily integrable on chip, may pave the way to a number of technological applications, from metrology to sub-millimeter wave generation.

No MeSH data available.