Coherent beam combining of multipass thin-disk lasers with active phase control

Abstract

Coherent beam combining and the development of thin-disk lasers have provided the ability to increase the output power of solid-state laser systems. Here, coherent beam combining by active phase control of one multipass thin-disk laser amplifier and one similar multipass setup is demonstrated with powers below 100 mW. Piston phase disturbances are measured via optical heterodyne detection and compensated for by piezo mirrors. For one double pass over the disk, a root mean square phase error of λ/69 was achieved. Mechanical vibrations < 5 kHz inside the multipass setup caused by the water cooling of the disk are the main source of phase noise. Thermal effects by the pumping diodes with 1 kW of optical power are negligible.