Investigations on the Bragg grating recording in all-silica, standard and microstructured optical fibers using 248 nm, 5 ps laser radiation

Abstract

The fabrication of Bragg reflectors in hydrogenated, all-silica, fluorine cladding depressed and microstructured optical fibers using 248 nm, 5 ps laser radiation, is investigated here. Comparative Bragg grating recordings are performed in both optical fibers, for investigating effects related to the scattering induced by the capillary micro-structure, to the photosensitivity and index engineering yield. Further, finite difference time domain method is employed for simulating the scattering from the above capillary structure and the nominal intensity reaching the fiber core for side-illumination. The maximum modulated refractive index changes inscribed in the standard, step-index fiber were of the order of 8.3×10−5, while the maximum refractive index changes inscribed in one of the microstructured optical fibers was 32% lower and 5.7×10−5, for nominal pulse intensities of 20 GW/cm2 and modest accumulated energy densities.

Keywords

• fiber bragg gratings
• microstructured optical fibres
• silica
• photosensitivity
• hydrogenation