Investigating the Influence of Laser Polarization on Filamentation Thresholds in Transparent Media via Supercontinuum Coherence

In this work, we experimentally investigate the characteristics of supercontinuum (SC) generation induced by femtosecond laser pulses with different polarization states in transparent medium. We employ a Mach-Zehnder Interferometer (MZI) to capture interference patterns during the filamentation process. The relative filamentation threshold, <i>P</i>_th, is measured for femtosecond laser pulses with different polarization states. The results demonstrate that the intensity of SC is strongly correlated with the polarization state of the incident laser pulses. At the same pulse energy, circularly polarized (CP) pulses suppress SC generation compared to linearly polarized (LP) pulses. Compared with weak external focusing, short-focal-length focusing significantly broadens the spectral range of SC. As the focal length of the focusing lens increases, the measured <i>P</i>_th values also increase. The <i>P</i>_th of the CP pulses is consistently higher than that of LP pulses. The experimental measurements of <i>P</i>_th for femtosecond lasers with different polarization states provide basic data support for the research on nonlinear characteristics.