Mechanisms of Index Change Induced by Near-UV Light In Hydrogen-Loaded Fibers

Abstract

Bragg Gratings in optical fibers have been formed using a wide variety of writing wavelengths ranging from the visible at 488 nm (using 2 photon excitation) to the vacuum-UV at 157 nm. [1-4]. Recently fiber gratings were fabricated by a one-photon process with near-UV light [5-8]. However results with near UV fabrication are contradictory: no Bragg grating was observed in the fibers in the absence of hydrogen loading [5,6], gratings in hydrogen-loaded fibers were transient [6], stable Bragg gratings were demonstrated with and without hydrogen loading [7,8]. Here we present the data that can help to explain these apparently contradictory results.