Performance scaling of laser amplifiers via coherent combination of ultrashort pulses

Laser systems emitting ultrashort pulses have become an indispensable tool in science. However, the performance of a single laser amplifier is limited by a variety of physical effects. The coherent combination of ultrashort pulses from parallel amplifiers offers a way to provide a new power-scaling opportunity. This concept can provide a simultaneous increase of the average power, pulse energy and peak power while preserving the beam quality and temporal pulse profile of a single-amplifier system. In order to successfully implement this approach, a number of aspects have to be considered. These include the realization of beam splitting and combination elements and the temporal matching of the pulses. Additionally, active stabilization techniques for the path lengths in the amplifier channels also have to be employed. In this thesis the coherent combination concept has been investigated theoretically and experimentally regarding these aspects. This includes the demonstration of high-power femtosecond fiber laser systems with four parallel channels as well as the compact integration of multiple amplifier channels in a multicore fiber.