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Nature Photonics 1, 336–342 (1 June 2007) | doi:10.1038/nphoton.2007.76

Operation of a free-electron laser from the extreme ultraviolet to the water window

W. Ackermann , G. Asova , V. Ayvazyan , A. Azima , N. Baboi , J. B|[auml]|hr , V. Balandin , B. Beutner , A. Brandt , A. Bolzmann , R. Brinkmann , O. I. Brovko , M. Castellano , P. Castro , L. Catani , E. Chiadroni , S. Choroba , A. Cianchi , J. T. Costello , D. Cubaynes , J. Dardis , W. Decking , H. Delsim-Hashemi , A. Delserieys , G. Di Pirro , M. Dohlus , S. D|[uuml]|sterer , A. Eckhardt , H. T. Edwards , B. Faatz , J. Feldhaus , K. Fl|[ouml]|ttmann , J. Frisch , L. Fr|[ouml]|hlich , T. Garvey , U. Gensch , Ch. Gerth , M. G|[ouml]|rler , N. Golubeva , H.-J. Grabosch , M. Grecki , O. Grimm , K. Hacker , U. Hahn , J. H. Han , K. Honkavaara , T. Hott , M. H|[uuml]|ning , Y. Ivanisenko , E. Jaeschke , W. Jalmuzna , T. Jezynski , R. Kammering , V. Katalev , K. Kavanagh , E. T. Kennedy , S. Khodyachykh , K. Klose , V. Kocharyan , M. K|[ouml]|rfer , M. Kollewe , W. Koprek , S. Korepanov , D. Kostin , M. Krassilnikov , G. Kube , M. Kuhlmann , C. L. S. Lewis , L. Lilje , T. Limberg , D. Lipka , F. L|[ouml]|hl , H. Luna , M. Luong , M. Martins , M. Meyer , P. Michelato , V. Miltchev , W. D. M|[ouml]|ller , L. Monaco , W. F. O. M|[uuml]|ller , O. Napieralski , O. Napoly , P. Nicolosi , D. N|[ouml]|lle , T. Nu|[ntilde]|ez , A. Oppelt , C. Pagani , R. Paparella , N. Pchalek , J. Pedregosa-Gutierrez , B. Petersen , B. Petrosyan , G. Petrosyan , L. Petrosyan , J. Pfl|[uuml]|ger , E. Pl|[ouml]|njes , L. Poletto , K. Pozniak , E. Prat , D. Proch , P. Pucyk , P. Radcliffe , H. Redlin , K. Rehlich , M. Richter , M. Roehrs , J. Roensch , R. Romaniuk , M. Ross , J. Rossbach , V. Rybnikov , M. Sachwitz , E. L. Saldin , W. Sandner , H. Schlarb , B. Schmidt , M. Schmitz , P. Schm|[uuml]|ser , J. R. Schneider , E. A. Schneidmiller , S. Schnepp , S. Schreiber , M. Seidel , D. Sertore , A. V. Shabunov , C. Simon , S. Simrock , E. Sombrowski , A. A. Sorokin , P. Spanknebel , R. Spesyvtsev , L. Staykov , B. Steffen , F. Stephan , F. Stulle , H. Thom , K. Tiedtke , M. Tischer , S. Toleikis , R. Treusch , D. Trines , I. Tsakov , E. Vogel , T. Weiland , H. Weise , M. Wellh|[ouml]|fer , M. Wendt , I. Will , A. Winter , K. Wittenburg , W. Wurth , P. Yeates , M. V. Yurkov , I. Zagorodnov & K. Zapfe

We report results on the performance of a free-electron laser operating at a wavelength of 13.7|[nbsp]|nm where unprecedented peak and average powers for a coherent extreme-ultraviolet radiation source have been measured. In the saturation regime, the peak energy approached 170|[nbsp]||[micro]|J for individual pulses, and the average energy per pulse reached 70|[nbsp]||[micro]|J. The pulse duration was in the region of 10|[nbsp]|fs, and peak powers of 10|[nbsp]|GW were achieved. At a pulse repetition frequency of 700 pulses per second, the average extreme-ultraviolet power reached 20|[nbsp]|mW. The output beam also contained a significant contribution from odd harmonics of approximately 0.6|[percnt]| and 0.03|[percnt]| for the 3rd (4.6|[nbsp]|nm) and the 5th (2.75|[nbsp]|nm) harmonics, respectively. At 2.75|[nbsp]|nm the 5th harmonic of the radiation reaches deep into the water window, a wavelength range that is crucially important for the investigation of biological samples.