We characterize the polarization properties of a supercontinuum (SC) generated in a GeO₂-doped photonic crystal fiber (PCF) to reveal the interplay between nonlinear broadening mechanisms of a pulse propagating in two independent fundamental modes associated to the principal axes of the fiber. Notably, we resolve self-phase modulation, self-shifted Raman solitons and dispersive waves within a set of orthogonal polarization states as they contribute to generate a broad spectrum spanning from 450 to 2150 nm. Interestingly, our experimental results feature a high degree of polarization at the edges of the spectrum in comparison to the region near the pump wavelength. We show that this modulation is caused by nonlinear spectral broadening. We also identify an additional depolarization mechanism preferentially acting on shorter wavelengths, indicative of a Rayleigh-like scattering effect due to the presence of intrinsic sub-wavelength defects in the fiber. Experiments rely on a free-space grating-based monochromator and a broadband polarizer to monitor the output SC and its linear polarization components along the principal axes of the PCF. Our results and experimental technique pave the way toward an improved standard for the characterization of broadband optical spectra and more efficient implementation of highly nonlinear fibers in a large range of polarization-sensitive applications.

我们表征了GeO _2中产生的超连续谱（SC）的极化特性掺杂光子晶体光纤（PCF），以揭示在与光纤主轴相关的两个独立基本模式下传播的脉冲的非线性展宽机制之间的相互作用。值得注意的是，我们解决了一组正交偏振态内的自相位调制，自位移拉曼孤子和色散波，因为它们有助于产生从450到2150 nm的宽光谱。有趣的是，与泵浦波长附近的区域相比，我们的实验结果在光谱边缘具有较高的偏振度。我们表明，这种调制是由非线性光谱展宽引起的。我们还确定了一种优先作用于较短波长的附加去极化机制，表示由于光纤中存在固有的亚波长缺陷而引起的瑞利散射效应。实验依赖于基于自由空间光栅的单色仪和宽带偏振器来监视输出SC及其沿PCF主轴的线性偏振分量。我们的结果和实验技术为在宽带偏振敏感应用中表征宽带光谱和更高效地实施高度非线性光纤铺平了道路。