Angular Scattering Pattern of Femtosecond Laser-Induced Refractive Index Modifications in Optical Fibers

Abstract

Focused femtosecond laser irradiation is used to induce light scattering modifications in the core of an optical fiber. This turns the fiber into a diffuse, line-shaped light source. The scattering is investigated by imaging almost the full solid angle far-field pattern for the first time. Additionally, an electromagnetic scattering model is developed to explain the observations. The findings herein change how the relationship between light scattering and the refractive index fluctuations is perceived by showing that the far-field scattering pattern is the power spectral density of the polarization current inside the scattering center. Further, the authors contribute to a better estimation of the scattering process by showing that the total scattering power scales quadratically with the laser-induced refractive index change and its volume.