DESIGN AND IMPLEMENTATION OF A TW-CLASS HIGH-AVERAGE POWER LASER SYSTEM

We describe the design, modeling and characterization of a titanium-do ped sapphire multipass, kilohertz amplifier system with output pulses of energy 4.4 mJ and duration 17 fs, giving a peak power of 0.26 TW. T he thermal lensing in the second amplifier stage is virtually eliminat ed by cryogenic cooling of the laser crystal. Gain-narrowing and shift ing of the amplified spectrum are reduced by tailoring the output spec trum of the oscillator and by using a low-loss multipass amplifier cha in. Fourth-order spectral dispersion was completely eliminated by usin g a prism pair in addition to adjusting the stretcher and compressor g rating separation and angle. We also numerically modeled the evolution of the pulse energy and spectral phase and amplitude through the ampl ifier system. The results of the model are in excellent agreement with measurements made using the technique of transient-grating frequency- resolved optical gating.