SELF-STARTING 6.5-FS PULSES FROM A TI-SAPPHIRE LASER USING A SEMICONDUCTOR SATURABLE ABSORBER AND DOUBLE-CHIRPED MIRRORS

We demonstrate self-starting 6.5-fs pulses from a Kerr-lens-mode-locke d Ti:sapphire laser with an average output power of 200 mW at a pulse repetition rate of 86 MHz, We have achieved a mode-locking buildup tim e of only 60 mu s; using a broad-band semiconductor saturable absorber mirror to initiate the pulse formation, The dispersion has been compe nsated with a prism pair in combination with improved double-chirped m irrors. The prism pair allows for the flexible adjustment of both the duration and the center wavelength of the pulse. The double-chirped mi rrors show a high reflectivity better than 99.8% over the full bandwid th of 300 nm and a controlled group delay over more than 250 nm, The c hoice of a proper output coupler turns out to be critical for ultrasho rt pulse generation directly from the laser.