[1] Univ London Imperial Coll Sci Technol & Med, Dept Elect & Elect Engn, London SW7 2BT, England
[2] Moscow MV Lomonosov State Univ, Fac Phys, Moscow 119992, Russia
[3] Univ Appl Sci, Dept Elect Engn & Informat Technol, D-93025 Regensburg, Germany
[4] Univ Oxford, Dept Engn Sci, Oxford OX1 3PJ, England
[5] Univ Osnabruck, Dept Phys, D-49069 Osnabruck, Germany