The FLASH optical laser systems

FLASH1 optical laser system

Pulse duration of the FLASH1 high power laser measured at BL1 with 51.7 +- 3 fs.


The FLASH1 pump-probe laser system

Two complementary optical lasers are available to user groups at FLASH1 in the FLASH experimental hall 'Albert Einstein'. First, a laser based on Ti:Sapphire technology is delivering a high energy pulse (up to 10 mJ, ~ 60 fs FWHM), albeit the repetition rate is limited to 10 pulses per second.
The second laser, based on optical parametric chirped pulse amplification, provides trains of ~ 20 µJ pulses ( ~ 100 fs FWHM) that map exactly onto the complex timing pattern of the FEL delivering several thousand pulses per second in bursts at 10 Hz with a minimum pulse spacing of 1µs. Both laser systems deliver a central wavelength of 800 nm. Second and third harmonic radiation can be generated at the experimental endstation.
The laser system is highly automated and remotely controllable from the experimental stations. An evacuated laser beam delivery system with relay imaging provides the pulses at BL1, BL2, BL3 and PG2.

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


Bastian Manschwetus
E-Mail: Bastian Manschwetus
Phone: +49 (0)40 8998 6093
Location: 222 / O1.106


Nominal parameters of the burst-mode OPA system

Parameters OPA


Pulse energy (µJ)


Pulse duration (fs)


Central wavelength (nm)


Repetition rate (MHz)


Macropulse rep.rate (Hz)


Macropulse duration (µs)


Energy stability (%, rms)



Nominal parameters of the Hidra mJ Ti:sapphire amplifier

Parameters 10 mJ amplifier


Max pulse energy (mJ)


Min pulse duration (fs)


Central wavelength(nm)


Rep. rate(Hz)


Energy stability(%, rms)


H. Redlin et al., The FLASH pump-probe laser system: Setup, characterization and optical beamlines, NIM A 635 , S88 (2011). (Article) or contact the DESY laser group.


The FLASH2 pump-probe laser system

The OPCPA pump probe laser system for FLASH2 will initially provide sub-20 fs laser pulses within bursts with a repetition rate of 10 Hz and an intra-burst repetition rate of 50 kHz. Each pulse in the 800 µs long burst can reach pulse energies up to 0.5 mJ with a wavelength centered at 800 nm. This corresponds to a peak power of > 22 GW with an intra-burst average power of 25 W.

The pump-probe laser beamline is designed to transport two beams with an excellent beam quality to two experimental end-stations at the same time. One of the two beams will be synchronized with a variable user delay to the FLASH FEL. The other beam is foreseen to allow pre-alignment of the optical setups for the upcoming user experiment at another end-station.

The following table summarizes the most important specifications available at the beamlines FL24 and FL26 in autumn 2018:

wavelength: 800 nm (fundamental center wavelength)
bandwidth: ~100 nm (TL <20 fs)
intra-burst-repetition rate: 50 kHz
number of pulses in burst: 1 - 40
pulse duration: 15 fs FWHM
timing jitter to FEL: < 50 fs rms
pulse energy: 0 – 500 µJ
polarization: flexible
focus size (1/eˆ2 diameter): FL24: < 100 µm, FL26: < 50 µm
peak intensity: FL24: > 10^14 W/cm², FL26: > 10^15 W/cm²
time delay to FEL: -4 ns to +4 ns, 10 fs resolution (larger delays optional)
energy stability: < 10% pulse-to-pulse peak fluctuation (3% rms)

Future upgrades foresee higher intra burst repetition rates (50, 100, 500, 1000kHz) at the same average output power as well as variable transform limited pulse durations up to 200 fs and wavelength tuning between 700 and 900 nm. Furthermore, different frequency conversions possibilities into the
VIS, IR and UV spectral range are planned for the future.


Tino Lang
E-Mail: Tino Lang
Phone: +49 (0)40 8998 6096
Location: 222 / O2.210