Spectral modulation and double-pulse formation in Kerr-lens modelocked Ti: sapphire laser

Besides the conventional single-pulset rain generation, the Ti: sapphire laser system sometimes produces two or even more pulses should proper conditions be satisfied. By treating the pulse propagati on within the laser gain medium with the help of split-step Fourier method, independently taking into account of the dispersion originating from the prism sequence, and making use of a generalized pulsewidth formula, the double-pulse formation process is numerically simulated in a self-consistent scheme. It is revealed that the condition of a tiny net negative dispersion with strong chirp is mandatory. The double-pulse generation manifests itself in a narrow range of physical parameters, thereby pose it as a metastable state.