Ultrafast Laser Fabrication of Bragg Waveguides in GLS Chalcogenide Glass

Authors:
Open Access
Publisher website
Google Scholar
Abstract
We present work on the fabrication of Bragg waveguides in gallium-lanthanum-sulfide chalcogenide glass using an ultrafast laser. Waveguides were written with a single pass while modulating the writing beam. The spatial and temporal profile of the writing beam was controlled during waveguide fabrication in order to control the shape and size of the waveguide cross-section. Over the last decade, ultrafast lasers have become the staple research tool of many research institutions. The applications of these lasers have moved beyond basic materials studies toward ever more complex systems, such as micro-fluidic devices [1-2], micromechanical actuators [3], and integrated monolithic waveguide lasers [4-5]. The materials used in these studies are often silica-based glasses, however considerable effort has been put toward the study of highly non-linear optical materials such as chalcogenide glass [6]. Waveguide fabrication in highly nonlinear, high-index materials presents significant challenges for ultrafast laser processing. High nonlinearities contribute to temporal distortion of focused femtosecond pulses, depleting pulse energy and distorting the focal volume, while a high index contrast further contributes to spatial distortions due to index mismatch induced spherical aberration. Building on previous work [7], we present the application of both spatial beam shaping and temporal pulse tailoring for the fabrication of Bragg waveguides in gallium-lanthanum-sulfide (GLS) chalcogenide glass. The waveguides presented here were fabricated using a Ti:sapphire system, delivering 150 pulses at 800 nm and a repetition rate of 250 kHz. The GLS sample was mounted to a motion stage system, incorporating a fixed focusing objective with a numerical aperture of 0.75. Distortions due to index-mismatch induced spherical aberrations were corrected at the focal volume with a cylindrical de-magnifying telescope, providing a demagnification factor of 3 in the y direction (perpendicular to the writing direction). Finally, the pulse-compressor of the laser was adjusted to provide a pulse duration of ~1.5 picoseconds, which was has been shown to give the lowest loss waveguides in GLS chalcogenide [7].

This publication has 8 references indexed in Scilit: