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Letter

Nature Physics 2, 456–459 (1 July 2006) | doi:10.1038/nphys338

High harmonic generation in the relativistic limit

B. Dromey , M. Zepf , A. Gopal , K. Lancaster , M. S. Wei , K. Krushelnick , M. Tatarakis , N. Vakakis , S. Moustaizis , R. Kodama , M. Tampo , C. Stoeckl , R. Clarke , H. Habara , D. Neely , S. Karsch & P. Norreys

The generation of extremely bright coherent X-ray pulses in the femtosecond and attosecond regime is currently one of the most exciting frontiers of physics–allowing, for the first time, measurements with unprecedented temporal resolution. Harmonics from laser–solid target interactions have been identified as a means of achieving fields as high as the Schwinger limit (E=1.3|[times]|1016|[nbsp]|V|[thinsp]|m|[minus]|1) and as a highly promising route to high-efficiency attosecond (10|[minus]|18|[thinsp]|s) pulses owing to their intrinsically phase-locked nature.