[1] Department of Appl. Phys. and DIMES, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
[2] Ctr. Rech. sur les Tres Basses Temp., assoc. à l'Univ. Joseph F., CNRS, BP 166, 38042 Grenoble-Cedex 9, France
[3] Inst. of Radio-Engineering and E., Russian Academy of Sciences, 11 Mokhovaya Str., 103907 Moscow, Russia