Abstract

Standard Yb:KYW based CPA-systems with pulse energies in the microjoule range generate pulses with durations limited to nearly 300 fs [1, 2]. This is mainly caused by spectral narrowing during the amplification process because the gain factor of the active medium is wavelength dependent. In order to achieve pulse durations shorter than 200 fs, different spectral broadening techniques, like spectral filtering, combination of overlapping gain spectra, can be applied. Another promising approach is based on the concept of spatially dispersive amplification [3, 4] which we have used in our experiments. The corresponding setup is shown in Fig. 1. Three SF6 prisms are used to divide the seed pulse, provided by an Yb fiber laser system with a pulse energy of 9 nJ around 1034 run into its spectral components. Due to the spatial separation, each spectral component passes through a different volume of the gain medium and is amplified independently. Thus, the pump can address each component individually and the amplified pulse spectrum is determined by the spectral pump distribution. The spectral gain profile does only influence the saturation behaviour of the spectral components. In our setup a flat spectral pump distribution has been arranged providing a spectral bandwidth of 25 nm.

© 2009 IEEE