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The femtosecond frontend consists of a commercial femtosecond laser
oscillator (Coherent Mira) delivering pulses with a duration of 100 fs
and energies around 4 nJ. An adjustable pulse stretcher is used to
realize the chirped pulse amplfication scheme
(CPA)
where a pulse is stretched in time, amplified and recompressed again.
A stretching ratio of 190 ps/nm keeps the peak powers below the
laser damage threshold of the optical components in the following
amplification chain.
The stretched pulse is then amplified by two Ti:saphire
regenerative amplifiers with a repetition rate of 10 Hz. The first one
is set up in a linear configuration while the second one is a ring
amplifier. The typical output energy is 30 mJ. Using ultra fast Pockels
cells the achievable intensity contrast ratio is better than 60 dB.
In addition a Mach-Zehnder interferometer can be used for generating
double pulses of variable delay, energy and different stretching ratio.
This is of particular interest for the generation of X-ray laser pulses.
Schematic overview of the PHELIX Femtosecond Frontend.
PHELIX Femtosecond Frontend
Key parameters are:
| ● Center wavelength: | 1053 nm |
| ● Spectral width: | > 6 nm |
| ● Pulse duration from femtosecond oscillator: | 100 fs |
| ● Pulse stretcher ratio: | 190 ps/nm |
| ● Maximum output energy: | 30 mJ at 1.2 ns |
| ● Contrast ratio: | > 60 dB |
| ● Repetition rate: | 10 Hz |
| ● Output mode: | TEM00 |
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