LASER L2 DUHA

LASER 2 Duha: 100 TW, 2 J, 50 Hz

The L2-DUHA Laser (Dual-beam Ultra-fast High energy OPCPA Amplifier) is designed to provide 100 TW-level pulses at a high repetition rate (50 Hz) at 820 nm, falling between L1-Allegra and L3-HAPLS in terms of peak power. The main role of L2-DUHA laser is driving laser-driven wakefield acceleration, where higher average power is desired and PW-level intensities aren’t necessarily required. L2-DUHA is the newest of the laser systems and is currently under development at ELI with expected completion in the first half of 2024.L2-DUHA is novel in that it is entirely based on DPSSL-pumped OPCPA. This is a departure from conventional Ti:Sapphire pumped by flashlamp pumped Nd-lasers and offers advantages in terms of average power handling and contrast. In addition to the 100 TW output, the L2-DUHA laser has a synchronized 5 mJ, 30 fs, 2.2 µm auxiliary output centered at 2 kHz. The large range of output wavelengths is what gives the laser its name, as “duha” is Czech for “rainbow.”

The general scheme for L2-DUHA is shown below; the seed for the 100 TW pulse train and the auxiliary output are both generated via supercontinuum in YAG crystals. The continuum is stretched to 2 ps and amplified via OPCPA with the picosecond pulse output of a 2 kHz Yb:YAG thin disk regenerative amplifier. The 820 nm seed for the 100 TW amplifier is stretched in an Offner Stretcher to 1.5 ns. The stretched pulses are then amplified via high energy OPCPA up to 4 J and compressed.

The pump laser for the high energy OPCPA is a diode pumped cryogenically cooled Yb:YAG multi-slab laser. The aggressive cooling and multi-slab crystal geometry allow the laser to work at very high average powers before suffering from deleterious thermal effects. For the first part of the project the laser will run at 20 Hz; then, after an upgrade to the pump laser head, the repetition rate will be increased to 50 Hz.

Parameter	Target 2024	Target 2026
Energy	2 J	3 J
Pulse Duration	25 fs	25 fs
Peak power	80 TW	120 TW
Repetition Rate	20 Hz	50 Hz
Contrast	1:10^-10 at 10 ps	1:10^-10 at 10 ps
Output laser beam RMS pointing stability	< 1 µrad	< 1 µrad
Beam size	120mm diameter, round	120mm diameter, round

Reference:

Jonathan Tyler Green, tyler.green@eli-beams.eu

LASER L2 DUHA

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