Bragg grating manufacturing in planar silica substrates

Abstract

Femtosecond laser pulses are more and more spread for the micro/nano-machining of various materials. They were successfully used for the manufacturing of Bragg gratings in optical fibres through the implementation of the so-called point-by-point, line-by-line and plane-by-plane processes. In this work, we report the use of such laser for Bragg grating manufacturing in pure fused silica planar substrates. In particular, we rely on the commercial system called Femtoprint. This machine has efficiently produced Bragg gratings from bulk silica following several steps. First of all, a waveguide was imprinted in the glass substrate by tight control of the laser pulses and path. Then, an access point was created at one edge of the substrate so that a standard optical fibre can be easily connected with the engraved waveguide for light injection and collection. This was again done with femtosecond laser pulses and a subsequent etching with KOH was performed to create the required open spaces in the substrate. Finally, a Bragg grating was imprinted within the waveguide thanks to a third femtosecond laser process. The reflected amplitude spectrum of the grating was characterized using a dedicated interrogator and the obtained experimental results will be presented in this paper.