title: Single-pulse picking at kHz repetition rates using a Ge plasma switch at the free-electron laser FELBE.
abstract: We demonstrate a system for picking of mid-infrared and terahertz (THz) radiation pulses from the free-electron laser (FEL) FELBE operating at a repetition rate of 13 MHz. Single pulses are reflected by a dense electron-hole plasma in a Ge slab that is photoexcited by amplified near-infrared (NIR) laser systems operating at repetition rates of 1 kHz and 100 kHz, respectively. The peak intensity of picked pulses is up to 400 times larger than the peak intensity of residual pulses. The required NIR fluence for picking pulses at wavelengths in the range from 5 μm to 30 μm is discussed. In addition, we show that the reflectivity of the plasma decays on a time scale from 100 ps to 1 ns dependent on the wavelengths of the FEL and the NIR laser. The plasma switch enables experiments with the FEL that require high peak power but lower average power. Furthermore, the system is well suited to investigate processes with decay times in the μs to ms regime, i.e., much longer than the 77 ns long pulse repetition period of FELBE.
authors.affiliation: Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Schmidt
authors.affiliation: Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Winnerl
authors.affiliation: Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Seidel
authors.affiliation: Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Bauer
authors.affiliation: Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Gensch
authors.affiliation: Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Schneider
authors.affiliation: Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Helm
mesh_terms: D004583:Electrons; D004867:Equipment Design; D005857:Germanium; D007259:Infrared Rays; D007834:Lasers; D055668:Photochemical Processes; D013997:Time Factors
chemical_list: D005857:Germanium