Abstract

The efficiency and quality of ultrashort pulse amplification decisively depends on the gain medium of the power amplifier. In order to achieve high average and peak powers while guaranteeing good beam quality and optimal pulse recompression, the chosen gain material must have both a wide gain bandwidth and good thermo-optical properties. One approach to obtain high power ultrashort pulses is to use the Chirped Pulse Amplification (CPA) technique with ytterbium doped crystals having a wide gain bandwidth. In the last amplification stage of the CPA chain, the optical spectrum must not suffer from gain narrowing and still be wide enough to have the conditions for an optimal recompression. Additionally, to reach high pulse energy and/or average power the crystal must be strongly pumped with a laser diode and a good thermal management is crucial to keep a good beam quality. It is not easy to find the right compromise to have at the same time good optical and thermal properties in a crystal. These two criteria are directly dependent on the crystal structure but need two antagonistic properties: a good phonon propagation ensuring an optimal thermal conductivity takes place in an ordered crystal structure but, conversely, a certain disorder in the host lattice facilitates a wide gain bandwidth [1].

© 2023 IEEE