PHOTON SCIENCE

Ultrafast optical pump-probe laser systems are available at both FLASH experimental halls.

Since the FEL and the optical laser are independent sources of fs-pulses, their synchronized operation is of vital importance to perform well defined pump-probe experiments. The overall timing jitter between the FEL and the optical laser at the experimental endstations is approximately 40 fs rms. More details

The optical lasers can be delayed with respect to the FEL pulses in a range of several ns.

FLASH1 pump-probe laser systems 

At the FLASH1 experimental hall two pump probe laser systems are available, both systems are highly automated and remotely controllable from the experimental stations:
(1) For the BL1 and BL3 endstations a laser based on Ti:sapphire technology is delivering a high energy pulse at 800 nm central wavelength (up to 10 mJ, ~ 60 fs FWHM), albeit the repetition rate is limited to 10 pulses per second. Second and third harmonic (central wavelength 400 nm respectively 267 nm) radiation can be generated close to the experimental endstation.
References:
H. Redlin et al., The FLASH pump-probe laser system: Setup, characterization and optical beamlines, NIM A 635 , S88 (2011). (Article)

(2) For the PG1 and PG2 endstations a laser system based on Yb- femtosecond laser technology was installed in 2020. The central wavelength is 1030 nm with a pulse duration < 100 fs (FWHM). It will provide a pulse pattern matched to the FEL pulse pattern with up to 1000 pulses at 1 MHz repetition rate per 10 Hz pulse train, thus up to 10000 pulses per second. Lower pulse repetition rates within the 1 ms pulse train length are also possible. Harmonic wavelength conversion modules (515 nm, 343 nm, 257 nm) are planned to be installed and available within 2021. The harmonic modules will provide also pulse durations of approximately 100 fs (FWHM). Preliminary specifications of the laser system are listed below. This laser system is available for the PG endstations only and is installed in a dedicated hutch close to the PG FEL beamline.

Note that this is a temporary though quite flexible solution for the experiments at the PG beamlines where almost all experiments require a pulse-train laser. We will unfortunately not be able to provide a pulse-train laser to the BL beamline endstations for some interim period, until we renovated the FLASH1 laser hutch and upgraded the laser systems to state-of-the-art technology in 2023.

FLASH2 pump-probe laser system

The FLASH2 pump-probe laser system is based on optical parametrical chirped pulse amplification (OPCPA). which enables higher flexibility in pulse properties than conventional Titan:Saphire or Yb:YAG femtosecond lasers.
Depending on user request the laser can be prepared either in a short pulse operation mode using the full amplification bandwidth between 700 and 900 nm to produce sub-20 fs pulses or in a long pulse operation mode with reduced spectral bandwidth and pulse durations in the order of 35 fs (FWHM). In that case the central wavelength can be tuned within seconds between 700 and 900 nm keeping pulse energy and pulse duration within 10% of the set-point. The wavelength stability is better than 5% of the bandwidth.
Harmonic wavelength conversion modules (central wavelength 400 nm, 267 nm) are available at the FL24 endstation. Also the second and third harmonic radiation can be tuned in central wavelength, please contact us for details.
The laser provides a pulse pattern matched to the FEL pulse pattern with up to 80 pulses at 100 kHz repetition rate per 10 Hz pulse train, thus up to 800 pulses per second. Lower pulse repetition rates within the 800 µs pulse train length are also possible.
Since 2020 we also provide an optical parameteric amplifier system at the FL24 endstation. This system provides infrared femtosecond pulses with tunable central wavelength from 1200 to 2400 nm at a few µJ level pulse energy. please contact us for details.

This laser is available at the FL24 and FL26 endstation. Nominal specifications of the laser system are listed in the table below.

Nominal parameters of the optical pump-probe lasers

CONTACT

Ingmar Hartl E-Mail: Ingmar Hartl Phone: +49 (0)40 8998 (9)2863 Location: 25B / 119