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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.

Tracks of modified material were written with femtosecond-laser pulses in neodymium-doped YAG crystals. Due to a stress-induced change of the refractive index, waveguiding beside the tracks and between two adjacent tracks with a distance of approximately 25 μm was observed. Loss measurements resulted in guiding losses of about 1.6 dB/cm for the double track waveguide. Spectroscopic investigations of the 4F3/2→4F11/2 transmission lines of the neodymium ions, which are close to the modified region, revealed a small stress-induced red shift of the lines. Laser oscillation of single-track waveguides and double-track waveguides was demonstrated with Ti:Sapphire laser pumping at a wavelength of 808 nm. Best laser performance with about 1.3 W output power at 2.25 W launched pump power was achieved using a double-track waveguide with a separation of 27 μm at an outcoupling transmission of 95%.