Femtosecond laser-induced filamentation typically exhibits pronounced spectral broadening,featuring a bright central white core encircled by concentric colored rings that span from the ultraviolet to the visible range...Femtosecond laser-induced filamentation typically exhibits pronounced spectral broadening,featuring a bright central white core encircled by concentric colored rings that span from the ultraviolet to the visible range and extend into the infrared.While ionization,self-steepening and self-phase modulation are widely accepted as explanations for the white spot,the underlying physics of colored rings remain inadequately understood by current models,such as Cherenkov radiation and four-wave mixing.In this study,inspired by the observation of similar discrete colored rings produced by cascaded four-wave mixing(CFWM)of intersecting beams,we systematically investigated the relationship between the colored rings in the white-light supercontinuum and CFWM.The CFWM model accurately predicted the correlation between color and divergence angles,thereby enhancing our understanding of spectral broadening in filamentation and providing guidance for optimizing the conversion efficiency and configuration of multi-wavelength ultrashort optical pulses in both spatial and spectral domains.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2024YFB3613900)the National Natural Science Foundation of China(Grant No.W2412044)+1 种基金the Russian Science Foundation(Grant No.25-49-00154)the Fundamental Research Funds for the Central Universities(Grant No.63253214)
文摘Femtosecond laser-induced filamentation typically exhibits pronounced spectral broadening,featuring a bright central white core encircled by concentric colored rings that span from the ultraviolet to the visible range and extend into the infrared.While ionization,self-steepening and self-phase modulation are widely accepted as explanations for the white spot,the underlying physics of colored rings remain inadequately understood by current models,such as Cherenkov radiation and four-wave mixing.In this study,inspired by the observation of similar discrete colored rings produced by cascaded four-wave mixing(CFWM)of intersecting beams,we systematically investigated the relationship between the colored rings in the white-light supercontinuum and CFWM.The CFWM model accurately predicted the correlation between color and divergence angles,thereby enhancing our understanding of spectral broadening in filamentation and providing guidance for optimizing the conversion efficiency and configuration of multi-wavelength ultrashort optical pulses in both spatial and spectral domains.
