Nonlinear pulse compression in a multi-pass cell

Area of Science:

• Laser physics
• Nonlinear optics
• Materials science

Background:

• High average power ultrashort pulse lasers are crucial for various scientific and industrial applications.
• Achieving significant pulse compression at high average powers presents challenges due to nonlinear effects like self-focusing.
• Existing methods often struggle to maintain beam quality and efficiency at elevated power levels.

Purpose of the Study:

• To demonstrate a robust scheme for nonlinear pulse compression at high average powers.
• To utilize fused silica as an effective nonlinear medium for spectral broadening.
• To achieve significant pulse duration reduction while maintaining excellent beam quality.

Main Methods:

• Employed a multi-pass cell configuration for nonlinear pulse broadening via self-phase modulation.
• Utilized a Yb:YAG-Innoslab laser system delivering >400 W average power and 850 fs pulse duration.
• Implemented a dispersive mirror compressor to remove spectral chirp and achieve pulse compression.

Main Results:

• Achieved spectral broadening of laser pulses from 1.6 nm to over 13.5 nm bandwidth at >400 W input power.
• Maintained near-diffraction-limited beam quality throughout the nonlinear process.
• Successfully compressed pulses to 170 fs duration at an output power of 375 W.
• The compression unit demonstrated an overall transmission efficiency exceeding 90%.

Conclusions:

• The demonstrated scheme enables efficient nonlinear pulse compression at high average powers.
• Fused silica proves to be a suitable nonlinear medium for this application, even above the critical self-focusing threshold.
• The method offers a practical solution for generating high-power, ultrashort laser pulses with high beam quality.