Cr:ZnSe laser (positive GDD)

For modelling, we have chosen the experiment described in Ref. [26] with the following simulation parameters: (corresponds to 1.5 W absorbed pump power at 1.61 $\mu$m), output coupling $\rho=0.01$, and GDD = 3500 fs$^2$ (material dispersion of the Cr:ZnSe crystal and acousto-optic modulator). As Kerr-lens mode locking mechanism was of the "soft-aperture" type, the exact value of the $\sigma$ parameter is unknown. The level of saturable losses $\gamma$ was estimated from the output power level to be up to two times higher than the losses due to the output coupler. In the simulation, the ranges of $\gamma$ and $\sigma$ are 0.01$\div$0.02 and 5$\div$10, respectively. Within these ranges, the modelling predicts the stable multipulsing with 2 to 28 pulses simultaneously present in the cavity. The typical pulse duration was 0.3-5 ps, distance between pulses 1 - 15 ps. Figure compares the simulated autocorrelation trace (pulse duration 4.4 ps, pulse distance 11.3 ps) with the experimental autocorrelation signal [26] (pulse duration 4.5 ps, distance 13.5 ps). The result was obtained using $\gamma = 0.02$ and $\sigma = 10$ parameters, both within the expected range of parameters and demonstrates validity of the model in the positive GDD regime.

Figure: Simulated and experimental autocorrelations of the multiple pulse Kerr-lens mode-locked Cr:ZnSe laser

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