Anomalous infrared conical emission during ordered multifilamentation in gases

Area of Science:

• Nonlinear Optics
• Laser Physics
• Quantum Optics

Background:

• Supercontinuum generation via laser filamentation is a key phenomenon in nonlinear optics.
• The frequency-angular structure (FAS) of supercontinua typically exhibits complex patterns.
• Controlling the FAS is crucial for various applications, including spectroscopy and optical coherence tomography.

Purpose of the Study:

• To investigate the effect of amplitude modulation on the FAS of femtosecond laser-induced supercontinua.
• To explore the potential for controlling supercontinuum generation through tailored laser pulse shaping.
• To understand the underlying physical mechanisms governing the modulated FAS.

Main Methods:

• Employing high-peak-power femtosecond laser pulses.
• Utilizing amplitude modulation techniques, specifically a 4-hole mask, to shape the laser beam.
• Generating supercontinua in both molecular and atomic gases.
• Analyzing the resulting frequency-angular structure of the emitted light.

Main Results:

• Amplitude modulation fundamentally changes the FAS of the supercontinuum.
• A 4-hole mask induces an inverted pattern of conical emission (CE).
• The inverted CE shows predominance in the Stokes wing of the spectrum, attributed to self-phase modulation and temporal pulse splitting.

Conclusions:

• Amplitude modulation offers a powerful tool for controlling the FAS of filament-generated supercontinua.
• The observed inverted CE pattern provides new possibilities for tailoring spectral and angular properties.
• This work opens avenues for advanced applications requiring precisely controlled supercontinuum light sources.