Author Affiliations

Z.G. Zhang,¹ J G. Wang,¹ J.R. Xu,¹ P.M. Fu,¹ H.J. Eichler,² B. Liu,² U. Taeuber,² A. Diening,³ G. Huber,³ X. L. Yan,⁴ X. Wu,⁴ and Y.D. Jiang⁴

¹Laboratory of Optical Physics and Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603. Beijing 100080. China

²Optisches Institut, Technische Universität Berlin. Strasse des 17, Juni 135, D-10623 Berlin, Germany (telephone: +49-30-31424701: fax: -49-30-31426888)

³Institut für Laser-Physik, Universität Hamburg, Jungiusstrasse 9a, D-20355 Hamburg, Germany

⁴Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100080, China