Mechanisms of the few-optical cycle pulse spectrum shift in Cr/sup 4+/:YAG laser

In this paper, we analyzed various possible causes and attribute the pulse down-frequency shift and its spectral extra-broadening in Cr/sup 4+/:YAG laser to the combined action of the intracavity third-order dispersion (TOD) and the stimulated Raman scattering (SRS) within an active medium. The results of the numerical simulations are in agreement with the experimental data obtained in the Kerr-lens mode-locked Cr/sup 4+/:YAG laser providing five optical cycle pulse generation. We showed that the pulse spectrum extra-broadening noticeably exceeding the gain bandwidth is analogous to the spectral continuum generation in fibers in the vicinity of the zero group-delay dispersion.