Hidden instabilities in the Ti : sapphire Kerr lens mode-locked laser

It is experimentally shown that pulse-to-pulse instabilities in the output of Kerr lens mode-locked Ti:sapphire lasers are usual and that they can aff ect some of the pulse variables (e.g., the spot size) and not others (e.g., pulse duration and energy). These instabilities are not detectable in the averaged signals (such as the autocorrelation of the pulse) that are custom arily used for controlling the laser. But, if they are present but are disr egarded, these instabilities have undesirable consequences in almost any ap plication. A simple way to detect and eliminate the instabilities is descri bed. (C) 1999 Optical Society of America.