Characterization of an Yb:YAG ceramic waveguide laser, fabricated by the direct femtosecond-laser writing technique

Using the direct femtosecond-laser writing technique tracks of modified material were written in an Yb(15%):YAG ceramic. Due to a stress-induced change of the refractive index between two parallel tracks waveguiding was achieved in channels between the tracks. Laser oscillation of these channel waveguides at a wavelength of 1030 nm was demonstrated with a maximum output power of 0.7 W. The investigation of two different outcoupling transmissions of 99% and 91% revealed that for the higher output coupling the slope efficiency is 35%, which is much lower in comparison to the case of lower output coupling with a slope efficiency of 65%. This effect may be explained by inversion dependent loss mechanisms.