Alexandrite-pumped alexandrite regenerative amplifier for femtosecond pulse amplification.

We demonstrate a regenerative amplif ier incorporating alexandrite as the gain medium that is pumped by an alexandrite laser. Temperature-altered gain permitted the 728-nm alexandrite pump laser, operating at room temperature, to pump a 780-800-nm alexandrite laser that was maintained at elevated temperatures. 200-fs pulses from a Ti:sapphire oscillator were amplif ied to the millijoule level. This system also amplif ied femtosecond pulses from a frequency-doubled Er-doped fiber laser.