Noise effects in Cherenkov Flux Flow Oscillator

A.A. Antonov, J. Mygind, A.L. Pankratov and A.V. Yulin
Institute for Physics of Microstructures of RAS, GSP 105,
Nizhny Novgorod, 603600, Russia
and
Department of Physics, Technical University of Denmark,
DK-2800 Lyngby, Denmark

The nonlinear dynamics of fluxons in Josephson systems with
dispersion [1] and thermal fluctuations is analyzed using
the "quasiparticle" approach to investigate the influence of
noise on the Cherenkov radiation effect. Analytical
expressions for the stationary amplitude of the emitted
radiation and its spectral distribution have been obtained
in an annular geometry [2]. It is demonstrated that noise
reduces the amplitude of the radiated wave and broadens its
spectrum. The effect of the radiated wave on the fluxon
dynamics leads to a considerably smaller linewidth than
observed in the usual Flux Flow Oscillator (FFO). A resonant
behavior of both the mean amplitude and the linewidth as
functions of bias current is found. The obtained results
enable an optimization of the main parameters (power,
tunability, and linewidth) of practical mm- and sub-mm wave
Cherenkov Flux Flow Oscillators (CFFOs).

The presentation at the conference "Future Perspectives of
Superconducting Josephson Devices" has been possible due to
financial support from Science Faculty of the University of
Sannio. This work has been supported by the Russian
Foundation for Basic Research (Project N 97-02-16928,
Project N 99-02-17544 and Project N 00-15-96620), and by
Ministry of High Education of Russian Federation (Project
N 992874), the Danish Natural Science Council, and the
Danish Research Academy.

1. V.V. Kurin and A.V. Yulin, Phys. Rev. B, v. 55, p. 11659
(1997).
2. A.A. Antonov, A.L. Pankratov, A.V. Yulin and J. Mygind,
Phys. Rev. B, v. 61, p. 9809 (2000).