Laminar phase flow for an exponentially tapered Josephson oscillator

A. Benabdallah*, J. G. Caputo+ and A. C. Scott# 

*Max Planck Institute
 for the Physics of Complex Systems
 Noethnitzer Str. 38
 D-01187 Dresden, Germany

+ Laboratoire de Physique Mathematique
  Universite Montpellier II
  34095 Montpellier cedex, France

# Institute of Mathematical modelling,
  Technical University of Denmark
  Lingby, Denmark

  and

  Department of Mathematics
  University of Arizona
  85719, Tucson, AZ, USA
  


Exponential tapering has previously been proposed as a means
to improve the performance of a Josephson flux flow
oscillator by extending the parameter range over which flux
quanta move smoothly (laminar flow) toward the load.
Extensive numerical results are presented here that support
this claim and demonstrate that exponential tapering
increases power output while improving the spectral purity
of the output voltage waveform. Since exponential tapering is
not expected to increase the difficulty of fabricating a flux
flow oscillator, we suggest that this feature should be
incorporated in future designs.