Several modelocking techniques have been demonstrated for Ti:sappnire [1,2]. We have used the self-focusing that takes place within the gain medium itself to modelock Ti:sapphire. The cavity mode changes resulting from this mechanism, that we call Kerr Lens Modelocking (KLM) , can be utilized and optimized in two important ways in order to sustain modelocked operation. At high peak powers better gain extraction can result from an improved overlap between the pump and cavity beams. Also, by introducing an intracavity aperture an adjustable intensity dependent loss can be created. When placed at a location within the cavity where the spot size decreases for increasing intensity the aperture becomes a fast saturable absorber . The effective cross section of this saturable absorber can be easily adjusted by changing the size of the aperture. This new control parameter provides a very powerful means for optimizing performance over a wide range of laser parameters.
© 1991 Optical Society of AmericaPDF Article