Nonlinear post-compression to sub-20 fs using a single-stage multipass cell filled with ambient air.

Area of Science:

• Nonlinear optics
• Ultrafast laser science

Background:

• Noble gas-filled multipass cells effectively compress high-energy, hundreds-of-femtoseconds laser pulses to tens of femtoseconds.
• Molecular gases offer stronger Raman nonlinearities than electronic Kerr nonlinearity, enabling greater spectral broadening and shorter pulses.

Purpose of the Study:

• To demonstrate a single-stage, air-filled multipass cell for spectrally broadening femtosecond laser pulses.
• To present a cost-effective and simple solution for generating few-cycle femtosecond pulses.

Main Methods:

• Utilizing ambient air at atmospheric pressure as the nonlinear medium within a multipass cell.
• Employing standard broadband mirrors without dispersion engineering.
• Broadening 145-μJ, 185-fs pulses with >90% throughput.

Main Results:

• Achieved significant spectral broadening of femtosecond laser pulses using ambient air.
• Compressed a fraction of the output pulses to sub-20 femtoseconds using a prism-pair compressor.
• Demonstrated the effectiveness of air as a nonlinear medium in a multipass cell setup.

Conclusions:

• An air-filled multipass cell provides a simple and cost-effective method for generating few-cycle femtosecond pulses.
• This approach bypasses the need for expensive noble gases and complex dispersion engineering.
• The demonstrated system offers a practical solution for ultrafast laser pulse generation.