Abstract

There is a growing interest in simple and robust directly diode-pumped femtosecond lasers. Ultrashort pulse lasers with the potential of high output power require a gain medium with broad amplification bandwidth, relatively large stimulated emission cross section and fluorescence lifetime and a good thermal conductivity. Using Yb-doped materials these requirements can be satisfied to a large extent. In addition, for the Yb³⁺ ion the quantum defect is small and excited state absorption and concentration quenching are absent. Specifically, the bandwidth of Yb:KGW [KGd(WO₄)₂] like that of Yb:glass has the potential to support sub-100-fs pulses and this monoclinic crystal has four times better thermal conductivity [1]. Broad-stripe diodes with several watts of output power in the wavelength range near 980 nm, corresponding to the absorption peak of Yb-doped materials, are available as low-brightness pump sources, but require a rather complex beam shaping optics in order to achieve proper mode matching [2]. Recent developments of high brightness diode lasers provide more than 2 W of cw output power near 980 nm.

© 2001 EPS