Dynamic behavior of postfilamentation Raman pulses

Area of Science:

• Nonlinear Optics
• Ultrafast Laser Physics

Background:

• Ultrashort laser pulses propagating in air undergo nonlinear phenomena like filamentation.
• Filamentation generates various spectral components, including a redshifted Raman pulse.

Purpose of the Study:

• To investigate the postfilamentation behavior of Stokes pulses generated during intense ultrashort pulse propagation in air.
• To analyze the divergence and intensity characteristics of these pulses and their implications for nonlinear optics.

Main Methods:

• Systematic analysis of pulse propagation dynamics.
• Far-field characterization of the Stokes transverse ring.
• Investigation of stimulated Raman scattering (SRS) in ionization-free channels.

Main Results:

• The redshifted Raman pulse exhibits greater divergence than the intense pump pulse postfilamentation.
• The far-field Stokes ring maintains sufficient intensity to induce SRS even after ionization ceases.
• An ionization-free light channel is identified within the Stokes transverse ring.

Conclusions:

• Postfilamentation behavior of Stokes pulses is characterized by increased divergence and sustained high intensity.
• The findings extend the potential applications of filamentation for remotely inducing third-order nonlinearities.
• The identified ionization-free channel offers a pathway for controlled nonlinear interactions.