Generation of a broad amplified spectrum in a femtosecond terawatt Ti:sapphire laser by a long-wavelength injection method

A long-wavelength injection method is proposed that will yield a broad amplified spectrum in a femtosecond terawatt Ti:sapphire laser. By injecting a seed pulse on the red side of the gain peak and amplifying it to a saturated fluence level, we could significantly compensate for the spectral narrowing that is due to the gain-narrowing effect by use of the amplifying characteristics of a positively chirped pulse in a gain-saturated regime, and 20-fs, 3-TW pulses could be demonstrated from a Ti:sapphire laser with two multipass amplifiers.