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Q: Fachverband Quantenoptik und Photonik

Q 30: Poster Nichtlineare optische Effekte und Lichtquellen

Q 30.2: Poster

Dienstag, 20. März 2007, 16:30–18:30, Poster C

High-order harmonic generation as a possible seed source for the BESSY-FEL — •Torsten Leitner, Atoosa Meseck, and Eberhard Jaeschke — Berliner Elektronenspeicherring-Gesellschaft für Synchrotronstrahlung m.b.H., Germany

The "Berliner Elektronenspeicherring-Gesellschaft für Synchrotronstrahlung" (BESSY) is planning to build a free electron laser (FEL), which is based on the concept of high-gain harmonic generation. In this concept, the FEL process is initiated by an external light field, the so-called seed. It is planned to use tunable lasers as seeding sources with wavelengths ranging from 230 nm to 460 nm. After this, a cascade of undulator–magnetic delay–undulator units has to be passed, where in each unit the light field is converted to a higher harmonic order until the desired output of 1 nm to 51 nm is achieved. A new approach is seeding directly at shorter wavelengths close to or in the final output range. To produce these short wavelengths high-order harmonic generation (HHG) in gases can be used. If a gas is irradiated by a high intensity laser, some of the atoms are ionized. Upon recombination, the atoms coherently radiate at integer multiples of the fundamental laser frequency. For this purpose a numerical simulation based on the "strong-field approximation" after M.Lewenstein et al. was developed, which calculates the single atom spectra and the propagation of the produced light through the gas. Using this radiation as the seed, the FEL process is analyzed via a Genesis 1.3 simulation, with special attention on the tranversal behavior of the seed and the produced FEL-light, as well as the frequency filtering effects in the FEL radiator.