Element Migration and Local Refractive Index Control in Silicate Glass by Femtosecond Laser Induced Element Redistribution

Femtosecond laser induced element redistribution (FLIER) in glass is a novel and noteworthy technique to fabricate photonic devices [1] . Publications over the past few years prove that FLIER is a capable tool to produce effective photonic devices, such as waveguides [2] , tapers [3] , optical amplifiers and lasers [4] . One of the key features of FLIER technology is the addition of glass modifiers that play the role of refractive index carriers (typically La 2 O 3 or BaO) together with other rather lighter constituents acting as fast diffusing elements (such as Na 2 O or K 2 O). Fs-laser irradiation activates a micrometric area within the glass, inducing a temperature gradient that ultimately causes thermophoretic migration amongst the species composing the glass. This migration results in a refractive index contrast high enough to produce efficient waveguides. In this work, we present the application of FLIER technology upon modified silicate glasses and the in-depth characterization of the waveguiding structures produced.