Sub-30-fs Yb:YAG thin-disk laser oscillator operating in the strongly self-phase modulation broadened regime

Area of Science:

• Laser Physics
• Ultrafast Optics
• Materials Science

Background:

• Yb:YAG (ytterbium-doped yttrium aluminum garnet) is a key material for thin-disk lasers (TDLs) due to its favorable properties.
• Standard mode-locking in Yb:YAG TDLs is limited to ~140 fs pulses due to its 8-nm gain bandwidth.
• Achieving shorter pulses requires operating in the self-phase modulation (SPM) broadened regime.

Purpose of the Study:

• To experimentally investigate and push the limits of pulse duration in Kerr-lens mode-locked Yb:YAG TDL oscillators.
• To explore and compare different laser configurations in the strongly SPM-broadened regime.
• To identify trade-offs between pulse duration, average power, efficiency, and intra-cavity peak power.

Main Methods:

• Utilized Kerr-lens mode-locking in an Yb:YAG TDL oscillator.
• Operated the laser in the strongly self-phase modulation (SPM) broadened regime.
• Optimized mode-locking parameters, including dispersion control with ion-beam sputtering (IBS) mirrors.

Main Results:

• Achieved a minimum pulse duration of 27 fs, the shortest reported for an ultrafast TDL oscillator.
• The pulse's spectral bandwidth (FWHM) exceeded the Yb:YAG gain bandwidth by over five times.
• Obtained 3.3 W average output power with 0.8 GW intra-cavity peak power.

Conclusions:

• Demonstrated that Yb:YAG TDLs can generate sub-30 fs pulses via strong SPM broadening.
• The achieved pulse durations and peak powers are suitable for advanced nonlinear optical experiments like high harmonic generation.
• This work establishes a new benchmark for ultrafast TDL oscillators.