Non-centrosymmetric crystals exploited as host matrices for rare earth active ions simultaneously enable a self-frequency doubling (SFD) process. In case of ytterbium doping it allows to obtain laser radiation at 1 µm and its SFD signal covering green spectral range. This mechanism is particularly interesting in case of mode-locked oscillators as the intensity within the crystal is much higher, thus increasing the conversion efficiency. Moreover, it can be also employed for cascaded χ(2) processes. Nevertheless, despite more than 20 years of development of Yb-doped mode-locked bulk lasers there are very few demonstrations of femtosecond oscillators with SFD properties [1-3].
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