Highly stable, high power hybrid fiber and Innoslab amplifier for narrow linewidth signals

Based on our study of a high stability ultra-narrow linewidth fiber amplifier for the gravitational wave detector LISA, we have set up a hybrid fiber and Innoslab amplifier for further power scaling into <100 Watt regime. The fiber amplifier can provide a seed power of up to 8 W at 1064 nm and a linewidth <10 kHz. The booster stage consists of an in-band pumped Innoslab amplifier, which is pumped by stabilized laser diodes at 880 nm. An output power of 437 W has already been demonstrated with almost diffraction-limited beam quality. Further investigations of power stability and modal properties are currently ongoing.