Microstructure, guiding performance and micro-spectroscopy characterization of Ce:LuAG crystal induced by direct femtosecond laser writing

Abstract

Dual-line waveguides in Ce:LuAG crystal are fabricated by femtosecond laser using 1030 nm, 450 fs pulses at a 100 kHz repetition rate. The microstructure and composition of femtosecond-laser induced waveguides are studied in detail using SEM, TEM and EDX elemental composition analyses. Efficient single-mode guidance is obtained in the type II waveguide structures with relatively low propagation loss along both TE and TM polarization at 632.8 nm. Based on confocal micro-Raman spectroscopy, the strain-affected regions and the lattice-damaged tracks are demonstrated. The contribution of each effect to the refractive-index distribution are quantitatively determined in combination with beam propagation calculations. The generation of yellow-green fluorescence emission is demonstrated under excitation at 405-nm, retaining well luminescent performance in the Ce:LuAG waveguide.