Some features of limitation of the output power of a mode-locked laser by self-focusing in the active element

The results are given of theoretical and experimental investigations of the influence of self-focusing in the active element on the energy characteristics of a mode-locked laser. Computer calculations of the output power for a fixed gain and laser resonator parameters are reported; allowance is made for the diffraction losses at the intracavity diaphragm. In this model the power is limited and it depends only weakly on the aperture in the diaphragm. The experimental value of the output power, ~7×10⁷ W, is in good agreement with the results of calculations.