Higher-order Kerr terms allow ionization-free filamentation in gases

Area of Science:

• Nonlinear optics
• Laser-matter interactions
• Plasma physics

Background:

• Self-channeling of ultrashort laser pulses is crucial for applications like laser ablation and atmospheric sensing.
• Previous models emphasized plasma generation as the dominant defocusing mechanism in filamentation.
• Understanding the precise mechanisms governing laser pulse propagation is essential for controlling light-matter interactions.

Purpose of the Study:

• To investigate the role of higher-order nonlinear optical effects in the self-channeling of ultrashort laser pulses.
• To contrast the contribution of nonlinear indices with plasma effects in filamentation.
• To accurately model and reproduce experimentally observed filament parameters.

Main Methods:

• Theoretical analysis incorporating higher-order nonlinear indices (n(4), n(6), n(8), n(10)).
• Numerical simulations of ultrashort laser pulse propagation in air and argon at 800 nm.
• Comparison of simulation results with experimental data on filament intensity and plasma density.

Main Results:

• Higher-order nonlinear indices (n(4) to n(10)) were identified as the primary source of defocusing in self-channeling.
• This contrasts with the established view that plasma effects are the dominant defocusing factor.
• The inclusion of these nonlinear terms successfully reproduced experimental intensities and plasma densities.

Conclusions:

• The study redefines the dominant mechanism behind self-channeling of ultrashort laser pulses.
• Higher-order nonlinearities play a critical role, offering a more complete understanding of filamentation.
• Accurate modeling requires considering these nonlinear optical effects for predicting laser-induced plasma phenomena.