The periodical phase structures writing into optical fibers through the protective coating
In course of this development directions, the methods of the fiber Bragg gratings writing are developed. The gratings are characterized with constant and varying period along the diffraction structure for the radiation introduction into fiber light guides covered with special protective coating being transparent for the ultraviolet radiation.
In addition, the works are carried out aimed at the fiber core formation by a focused femtosecond laser beam. It uses the effect of a refractive index change in multi-photon light absorption by the fiber material. Because of the nonlinear mechanism of interaction with the dielectric medium, creating the desired lattice structures turn out to be possible. These structures are characterized with a complex profile and a relatively high transparency of acrylic fiber coating for the radiation of the Ti:Sa femtosecond laser (wavelength 800 nm). Thus, writing the gratings with phase shifts as well as the chirped gratings and relevant superstructures into optical fiber without removing the protective acrylic shell is becoming feasible.