Depolarization of the supercontinuum induced by linearly and circularly polarized femtosecond laser pulses in water

The supercontinuum (SC) is generally assumed to inherit the polarization of the incident pulse in isotropic media. In this study, we experimentally investigated the polarization properties of SC spectra induced by different polarized femtosecond lasers in water. The results show that the extent of depolarization of the SC induced by a quasicircularly polarized pulse is more pronounced than that of a quasilinearly polarized pulse. In terms of the different spectral components, the long-wavelength components experienced more depolarization, and the short-wavelength components tended to be linearly polarized for both polarized input femtosecond lasers. The depolarization mechanism can be attributed to two factors, namely, the energy coupling between the two polarized components of the input femtosecond pulse, and the various degrees of nonlinear birefringence experienced by different spectral components of the SC during propagation.