Measurement of stress-induced birefringence in a thin-disk laser with full-Stokes polarimetry.

Stress-induced birefringence leads to losses in solid-state laser resonators and amplifiers with polarized output beams. A model of stress-induced birefringence in thin disks is presented, as well as measurements of stress-induced birefringence in a thin disk in a multi-kilowatt oscillator. A full-Stokes imaging polarimeter was developed to enable fast and accurate polarimetric measurements. Experimental and simulated results are in good agreement qualitatively and quantitatively and show that the polarization loss due to stress-induced birefringence is negligible for ytterbium-doped thin disks with a thickness around 100 µm but becomes relevant in thicker disks. It is concluded that stress-induced birefringence should be taken into consideration when designing a thin-disk laser system.

Thin-disk laser system operating above 10 kW at near fundamental mode beam quality.

We report on a thin-disk laser system with more than 10 kW of output power and a beam quality of M2=1.76 at an overall optical-to-optical efficiency of 51%. The system consists of two thin-disk laser oscillators and a thin-disk multi-pass amplifier system. To reach high output powers while maintaining good beam quality, the output beams of two identical laser oscillators are polarization-combined. Subsequently, the beam is amplified in a multi-pass system. To the best of our knowledge, this is the highest output power achieved for a thin-disk laser system with a beam quality close to fundamental mode.