Contact person: Kiss Bálint PhD, e-mail: balint.kiss_at_eli-alps.hu
The Mid-Infrared laser system (MIR system) has been delivering 140 µJ, 4-cycle pulses centred at 3.2 µm at 100 kHz repetition rate with < 1% RMS stability over 8+ hours of operation per day since November 2017 (Fig. 1). The system has unique <100 mrad CEP stability together with precise CEP control during experiments .
Fig1. Schematic layout of the MIR laser
The most important output parameters are shown in Table 1. The energy can be slowly varied continuously from 15 µJ to 140 µJ while other parameters are subject to change. The CEP setpoint can be adjusted continuously between 0 and 2 π. The pulse duration can be stretched up to 150 fs by the Dazzler or via material dispersion.
Table 1. Measured laser parameters
*By taking into account the optical losses related to beam steering and manipulation (including telescoping, presicope/dogleg, chirp compensation and sampling for in-line diagnostics) required for user experiments in general.
**By Using 2-wire grid polarizers.
***Upon detuning the central wavelength, the available power is in the ~4-9 W regime with >2.5 % stability, and the compressed pulse duration increases to the >150 fs range. Active CEP stabilization is available based upon best effort.
Concerning laser operation, the energy stability over a day long operation is excellent (see Fig. 2), with stable pulse duration (Fig 3).
Fig 2. Pulse energy vs time; the inset shows the full power part (>14W, 140uJ).
Fig 3. FROG maps of the 4-cycles compressed pulse.
Post-compressed 2-cycle output
The output of the MIR OPCPA is post-compressed to 2 cycles in a post-compression stage . Spectral broadening is performed in mm-thick dielectric (BaF2) and semiconductor (Si) plates in a confocal geometry, followed by recompression in a bulk dielectric (CaF2) window combined with a set of reflections on dispersive mirrors (Optoman). We provide 2-cycle pulses (see Fig. 5) with energies up to 75 µJ (7.5 W), with long-term CEP (240 mrad) and power stability (2.1%) for several hours without interruption (see Fig. 6). The parameters of this output are listed in Table 2 below.
Fig. 5. Measured (a) and reconstructed (b) SH-FROG trace, reconstructed temporal intensity profile (c) and spectrum with spectral phase (d).
Fig. 6. Four-hour measurement of the CEP (top), the power (middle) and the spectral (bottom) stability.
Table 2. Measured laser parameters of the post-compressed output
*By taking into account the optical losses related to beam steering.
**By using 2-wire grid polarizers.
• Spectrometer 1.5-5 um (Mozza, Fastlite)
• Scanning FROG all reflective, down to sub-2 cycles @ 3mm
• TIPTOE, down to single cycle @ UV to MIR.
• Single-shot CEP detection (Fringeezz, Fastlite 10 kHz; TOUCAN, ELI-ALPS, 100 kHz)
• Beam profilers (IRC912 MIR CCD camera, Ophir Nanoscan, Pyroview DIAS Infrared Bolometric camera)
• Wavefront sensor (SID4-DWIR, Phasics
 N. Thiré, R. Maksimenka, B. Kiss, C. Ferchaud, T. Pinoteau, H. Jousselin, S. Jarosch, P. Bizouard, V. Di Pietro, E. Cormier, K. Osvay and N. Forget, “Highly-stable, 15 W, few-cycle, 65 mrad CEP-noise mid-IR OPCPA for statistical physics”, Optics Express 26(21), 26907-26915 (2018) https://doi.org/10.1364/OE.26.026907
 R. Flender, M. Kurucz, T. Grosz, A. Borzsonyi, U. Gimzevskis, A. Samalius, D. Hoff and B. Kiss, “Dispersive mirror characterization and application for mid-infrared post-compression”, Journal of Optics 23 (2021) 065501 (9pp) http://dx.doi.org/10.1088/2040-8986/abf88e