CONCLUSION

In conclusion, we presented the model, which can be usable for the numerical optimization of the KLM lasers and is governed by only four basic parameters: difference between saturated gain and linear loss, GDD, modulation depth and saturation intensity of the fast saturable absorber. On the basis of this model, the KLM abilities of the Cr-doped Zinc-chalcogenides were estimated. It was shown, that the strong SPM inherent to these media and destabilizing the single pulse operation can be overcomed by the choice of the appropriate GDD, pump, modulation depth and saturation parameter of the Kerr-lensing induced fast saturable absorber. It was demonstrated also, that the continuum amplification is reduced by the large gain saturation and the destabilizing nonlinear phase shift decreases due to high linear refraction and large generation wavelength in the media under consideration. As a result, the Cr:ZnTe possesses the lowest KLM threshold, however strong SPM constrains the achievable pulse power for this laser. The best stability for the highest energy flux and the shortest pulse duration (19 fs) are achievable in Cr:ZnS. Cr:ZnSe lies between these media. The presence of the third-order dispersion increases the minimum achievable pulse durations up to 34 - 40 fs and causes the strong (up to 140 nm) Stokes shift of the generation wavelength. However, the latter effect does not reduce noticeably the pulse energy. On the whole, the Cr-doped Zinc-chalcogenides have the prospects of sub-50 fs generation that amounts to only few optical cycles around 2.5 $\mu$m.

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