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.

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:

(1) 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.

(2) A laser based on optical parametric chirped pulse amplification (OPCPA), 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.
Note: This laser system will be retired in summer 2020.

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.

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

New FLASH1 burst mode pump-probe laser for the PG instruments will be available starting mid-2020

During the FLASH Summer shutdown 2020 the pulse train laser at FLASH1 will be retired. As replacement a new laser system based on Yb- femtosecond laser technology will be installed in Spring 2020, 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. Lower pulse repetition rates within the 1 ms pulse train length are also possible. Preliminary specifications of the new laser system are listed below. The new laser system will be available for the PG instruments only and will be installed in a dedicated hutch close to these instruments.
Harmonic wavelength conversion modules (515 nm, 343 nm, 257 nm) are planned to be installed shortly after commissioning of the laser, but will most likely not be available for the 2nd half of 2020. The harmonic modules will provide also pulse durations of approximately 100 fs (FWHM). We are currently investigating the feasibility to add an optical parametric amplifier for generating femtosecond pulses with central wavelengths between 1.5 and 5 µm.
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 upgraded the FLASH1 laser hutch and laser systems to our new 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).

The laser can be operated in a short pulse mode using the full amplification bandwidth between 700 and 900 nm to produce sub-20 fs pulses.

At reduced spectral bandwidth fast wavelength tuning is available. The central wavelength can be tuned within 30s between 700 and 900 nm keeping pulse energy and pulse duration within 10% of the set-point. After the 30s tuning time, the wavelength stability is better than 5% of the bandwidth.


 

Nominal parameters of the optical pump-probe lasers

beamline

number of pulses


rep.
rate [kHz]

λc [nm]

Δλ
[nm] FWHM

Ep [µJ]

tp [fs]

⌀on target

[µm] (1/e2)

BL1

1

 

810

20

5000

60

70

 

1

 

405

3

1000

100

60

 

1

 

271

2

100

50

50

 

1

 

tunable (OPA)

ask

ask

ask

ask

BL2 / BL3

1

 

810

20

5000

60

ask

 

1

 

tunable (OPA)

ask

ask

ask

ask

PG1/PG2

1-1000

100-1000

1030

20

20

100

ask

 

1-1000

100-1000

515

7

5

150

ask

 

1-1000

100-1000

343

ask

ask

ask

ask

FL24

1-80

100

tuneable 700-900

10 < Δλ < 100

200

20 < tp < 100

200

 

1-80

100

400

ask

ask

ask

ask

 

1-80

100

270

ask

10

100

ask

FL26

1-80

100

tuneable 700-900

10 < Δλ < 100

200

20 < tp < 100

200

CONTACT

Manschwetus
Bastian Manschwetus
E-Mail: Bastian Manschwetus
Phone: +49 (0)40 8998 6093
Location: 25b / O1.128