Josephson flux-flow oscillator: The microscopic tunneling approach

Abstract

Citation: GULEVICH, D.R., KOSHELETS, V.P. and KUSMARTSEV, F.V., 2017.Josephson flux-flow oscillator:The microscopic tunneling approach.Physical Review B, 96 (2), 024515-1 -024515-12.Additional Information:• We elaborate a theoretical description of large Josephson junctions which is based on Werthamer's microscopic tunneling theory. The model naturally incorporates coupling of electromagnetic radiation to the tunnel currents and, therefore, is particularly suitable for description of the self-coupling effect in Josephson junction. In our numerical calculations we treat the arising integro-differential equation, which describes temporal evolution of the superconducting phase difference coupled to the electromagnetic field, by the Odintsov-Semenov-Zorin algorithm. This allows us to avoid evaluation of the time integrals at each time step while taking into account all the memory effects. To validate the obtained microscopic model of large Josephson junction we focus our attention on the Josephson flux-flow oscillator. The proposed microscopic model of flux-flow oscillator does not involve the phenomenological damping parameter, rather the damping is taken into account naturally in the tunnel current amplitudes calculated at a given temperature. The theoretically calculated current-voltage characteristics is compared to our experimental results obtained for a set of fabricated flux-flow oscillators of different lengths.

Flux-flow Josephson oscillator as the broadband tunable terahertz source to open space

“…To take into account the superconducting state of the antenna and microstrips, the London penetration depth for thin Nb films λ L = 85 nm is used, and the SiO 2 dielectric constant ε = 4.2 was taken for thin films. Calculating the real FFO output impedance, which is frequency dependent, is an extremely complicated task due to selfcoupling and standing-wave effects, 15,22 and so the impedance was taken to be constant and equal to 0.5 Ω.…”

“…The flux-flow oscillator (FFO) based on a long Josephson junction with a length much more than the Josephson penetration depth (l ≫ λ J ) is a promising THz source, due to its excellent operating bandwidth, which can be up to 100% of the central frequency. 1 The FFO was studied experimentally [1][2][3][4][5][6][7][8] and theoretically [9][10][11][12][13][14][15] and, finally, was utilized as the local oscillator (LO) of the heterodyne THz receiver in the real flight mission TELIS, 16,17 for atmospheric research. In this mission, as well as in other studies on the FFO and its applications, it was used as an on-chip planar source.…”

Источник Терагерцевого Излучения В Открытое Пространство На Основе Распределенного Джозефсоновского Перехода

“…Неполное соответствие обусловлено рядом упрощений, принятых при численном моделировании. Так, например, в расчетах выходная мощность РДП положена не зависящей от частоты, тогда как в реальной системе мощность зависит как от режима работы генератора [17,18] (резонансный режим либо режим вязкого течения вихрей), так и от согласования излучения РДП с выходной линией передачи при конкретной частоте генерации. Кроме того, при моделировании сверхпроводниковых линий передачи бралась упрощенная модель.…”

Terahertz Source Radiating to Open Space Based on the Superconducting Flux-Flow Oscillator: Development and Characterization

“…One of those is damping of the signal in the experiment caused by increased surface losses in Nb lines at frequencies higher than 650 GHz, in accordance to the Mattis-Bardeen theory. Another reason for damping at higher frequencies is self-pumping effect in a long Josephson junction at the voltage above V g /3 [17], [18].…”