Amplification of kW peak power femtosecond pulses in single quantum well InGaAs tapered amplifiers

The amplification of ps and fs pulses with peak powers of up to 4.5 kW has been investigated in a single quantum well InGaAs tapered amplifier. The pulses with durations of 100 fs or 2 ps were generated by a modelocked titanium–sapphire laser. The amplified pulses indicate strong gain saturation and carrier generation due to photon absorption in the laser active region which causes a temporal broadening of the amplified pulses as well as modifications of the optical spectrum. The gain recovery time was measured by a pump–probe experiment. The experimental results are analyzed with respect to the sub-ps gain dynamics which is described by a relaxation time approximation.