Kerr-lens mode locking with minimum nonlinearity using gain-matched output couplers.

Area of Science:

• Optics and Photonics
• Laser Physics
• Ultrafast Science

Background:

• Kerr-lens mode locking (KLM) is a crucial technique for generating ultrashort laser pulses.
• Traditional KLM often requires high intracavity pulse energies and strong nonlinear effects.
• Gain filtering in broadband lasers can limit the achievable pulse durations and stability.

Purpose of the Study:

• To demonstrate broadband Kerr-lens mode locking at significantly reduced mode-locking strength.
• To compensate for gain filtering effects in ultrafast lasers.
• To achieve robust generation of sub-8 femtosecond pulses with good beam quality.

Main Methods:

• Utilized a gain-matched output coupler to counteract gain filtering.
• Employed a Ti:sapphire laser system.
• Operated the laser at low pump powers, near the continuous-wave (cw) lasing threshold.

Main Results:

• Successfully demonstrated robust Kerr-lens mode locking with greatly reduced strength.
• Generated output pulses with durations less than 8 femtoseconds (<8 fs).
• Achieved good beam quality in the generated ultrashort pulses.

Conclusions:

• The developed gain-matched output coupler approach enables KLM with reduced nonlinear requirements.
• This technique is effective even at low pump powers, simplifying laser operation.
• The method's reliance on flexible dielectric coatings makes it adaptable to various laser gain media for broad spectral coverage.