All-optical Q-switching limiter for high-power gigahertz modelocked diode-pumped solid-state lasers

Area of Science:

• Laser Physics
• Nonlinear Optics
• Materials Science

Background:

• Passively mode-locked diode-pumped solid-state lasers (DPSSLs) operating at gigahertz (GHz) repetition rates are prone to Q-switching instabilities.
• Semiconductor saturable absorber mirrors (SESAMs) mitigate these instabilities but are limited by damage thresholds at higher average output powers.
• Existing methods to overcome these limitations often require complex alignment or external amplification.

Purpose of the Study:

• To present a novel, all-optical Q-switching limiter mechanism for stabilizing GHz SESAM mode-locked lasers.
• To increase the potential output power of SESAM mode-locked lasers without compromising stability.
• To enable the generation of high-power, multi-gigahertz frequency combs.

Main Methods:

• Implementation of a Kerr lens induced negative saturable absorber within the laser cavity.
• Careful cavity design to ensure the limiter operates within the stable regime without critical alignment.
• Quantitative analysis of the Kerr lens limiter's impact on mode-locked operation and pulse characteristics.

Main Results:

• Demonstration of a high-power diode-pumped Yb:CALGO solid-state laser generating sub-100 fs pulses at 5 GHz repetition rate.
• Achieved average output power of 4.1 W with a peak power of 7.5 kW directly from the oscillator.
• Successful suppression of Q-switching instabilities, allowing operation beyond the typical SESAM damage threshold.

Conclusions:

• The developed all-optical Q-switching limiter effectively stabilizes GHz SESAM mode-locked lasers.
• This method allows for significantly increased output power without external amplification or pulse compression.
• Provides a pathway towards compact, high-power, multi-gigahertz frequency combs based on DPSSLs.