Integrated Waveguides and Bragg Gratings UV Written with 213Nm Light

Abstract

Direct UV writing is capable of fabricating low-loss channel waveguides, couplers and Bragg gratings in planar silica by translation through a focused UV beam. Devices are typically fabricated using 244nm laser light, relying on the photosensitivity provided by doping to induce sufficient refractive index change necessary to form waveguides. However, these devices also require hydrogen and deuterium loading prior to writing to induce sufficient refractive index change to form waveguides [1]. Hydrogenation not only requires additional processing but over time the hydrogen present within the silica depletes, which can cause variation of the final written structures. Deep UV light at 213 nm has previously been used to inscribe strong fibre Bragg gratings (FBGs) in hydrogen-free Ge-doped fibres achieving an index change of 1.2×10−3 [2]. Here we present the first use of a 213 nm UV laser to induce index change sufficient to simultaneously define waveguides and Bragg gratings in planar silica without hydrogenation. This would potentially allow writing of large area or two-dimensional devices without variation due to outgassing.