Relaxation of gain narrowing problem in a multi-pass Ti:sapphire laser system using a long wavelength injection method

With the advancement of chirped pulse amplification (CPA) and femtosecond Ti:sapphire laser technologies, femtosecond terawatt lasers have been developed and applied to a variety of research fields. Due to their broad gain bandwidth, Ti:sapphire lasers with duration less than 50 fs have been constructed at a terawatt power level by amplifying a femtosecond seed pulse, and the generation of sub 30-fs, multi-terawatt pulses has been successfully achieved using a regenerative pulse shaping technique in the past a few years. While the regenerative pulse shaping has been successful in overcoming the gain narrowing effect in regenerative amplifiers, there has been almost no proper solution for a gain narrowing problem in multi-pass amplifiers. In our work, we propose a long wavelength injection (LWI) method to relax the gain narrowing problem in multipass amplifiers.