Two statistical regimes in the transition to filamentation

Area of Science:

• Nonlinear Optics
• Laser Physics
• Plasma Physics

Background:

• Filamentation of ultrashort laser pulses in air is a key phenomenon in nonlinear optics.
• The critical power for filamentation marks a transition in laser beam propagation.
• A precise definition of the filamentation threshold remains elusive.

Purpose of the Study:

• To experimentally investigate spectral fluctuations of ultrashort laser pulses near the critical power for filamentation.
• To analyze the transition dynamics of spectral intensity and probability distribution functions.
• To provide insights into the ambiguous definition of the filamentation regime boundary.

Main Methods:

• Experimental setup for propagating ultrashort laser pulses in air.
• Varying laser peak power to approach the critical power for filamentation.
• Spectroscopic analysis of output pulses, including probability distribution functions.

Main Results:

• Spectral broadening of laser pulses as they approach the filamentation regime.
• Continuous increase in spectral intensity at the center of the spectrum.
• Appearance of a bimodal probability distribution function at spectral edges for intermediate energies.

Conclusions:

• The observed dual behavior in spectral transitions complicates a univoquial definition of the filamentation threshold.
• This study offers a new perspective on the long-standing ambiguity in defining the filamentation regime boundary.
• Understanding these spectral dynamics is crucial for controlling nonlinear light propagation.