Freiburg 2024 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 46: Lasers I

Q 46.8: Vortrag

Donnerstag, 14. März 2024, 12:45–13:00, HS 3118

NOPA rainbow: 10 fs regime pulses tunable over more than an octave — •Ferdinand Bergmeier and Eberhard Riedle — Lehrstuhl f. BioMolekulare Optik, Fakultät f. Physik, LMU München

We combine a contemporary Yb-based 250 fs industrial-grade pump laser with a newly devised and comprehensively engineered noncollinear optical parametric amplifier (NOPA). The NOPA employs easily interchangeable 515 and 343 nm pumping, facilitating fundamental tunability from 390 to 950 nm without any gaps. Output pulse energies of some uJ are reached in a single amplification stage with a clean Gaussian beam shape. The repetition rate can be varied between 1 and 200 kHz without adjustments at constant pulse parameters. A single stage of second harmonic generation (SHG) extends this range down to below 220 nm. The spectral width across all centre wavelengths is sufficient for sub-10 fs pulses. We routinely achieve pulse lengths between 10 and 20 fs. The system has stably run without any adjustments for three months.

To scrutinize the characteristics of the pump laser/NOPA combination, we developed a detector capable of shot-to-shot measurements at a rep rate of 200 kHz. This detector was employed to analyse the shot-to-shot fluctuations and correlation of the NOPA at various repetition rates and pulse picker settings of the pump laser. Beyond the overall rms of the output pulses all relevant nonlinearly generated pulses inside the NOPA were compared and correlated to the pump laser behaviour. It was found that the long-term fluctuations of the NOPA output are below 0.5% at a 0.1% level of the pump laser.

Keywords: octave wide tuning; noncollinear optical parametric amplifier (NOPA); Yb-based pump laser