Ti:sapphire laser (negative GDD)

The multipulsing behavior of this laser is well-documented (see, for example, [19,20,4,13]). We will apply our model to the experiment from Ref. [13] inasmuch as in this work the stability of the single pulse generation was the subject of the special investigation and comprehensive experimental data is available. We choose the following simulation parameters: $P$ = 1.44 $\times 10^{-3}$, corresponding to 2.5 W pump power at 488 nm with 28 $\mu$m Gaussian beam diameter; output coupling $\rho$=0.025; $\gamma$=0.044, 0.024, 0.015, that corresponds to 1.5, 2 and 2.5 mm aperture diameters, respectively. We obtained the following results of the simulations. For the maximal diffraction loss ($\gamma$=0.044) both CW and ultrashort pulse generation are suppressed as it took place in the experiment. The choice of the other two values of $\gamma$ results in the stable single pulse generation. The corresponding regions are shown in Fig. , where the curves, as usually, represent the boundaries of the single pulse stability regions. $\gamma$=0.024 is close to the optimal value of the modulation depth (see Fig. 1 in [13]). In this case the single pulse generation takes place in the widest region on our parametrical plane (solid curve). The minimal pulse duration is 42.5 fs, which is in good agreement with the experimental data (see Fig. 2 in [13]). The estimated experimental values of $\sigma$ were $\approx$0.5$\div$0.7, which are close to the optimal values in our simulations (see Fig. ) and are located on the lower stability boundary. The destabilization for these $\sigma$ occurs when $D>$-350 fs$^2$. This quite agrees with the experimental data.

Figure: The regions of the pulse stability for Ti:sapphire. Solid and dashed lines represent the single pulse stability boundary for $\gamma$=0.024 and $\gamma$=0.015, respectively.

The decrease of $\gamma$ produces the shortening of the single pulse stability region (dashed curve in Fig. ). In this case, as it was found in [13], the single pulse operation is suppressed by the multipulsing or CW generation. As a result, the minimal pulse duration increases due to higher minimal $\vert D\vert$. This comparison demonstrates that the model is in quantitative agreement with the experimental data for the Ti:sapphire laser and the pulse destabilization scenarios in question have a general character.

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