Ultrafast pulse optimization using two-photon absorption induced thermal lens

We present a method that uses the two-photon induced thermal lens effect as feedback signal in an ultrafast pulse shaping technique for femtosecond pulse optimization in a closed-loop evolutionary algorithm. This approach presents robustness equivalent to those that employ other nonlinear processes but has the advantage that the sample does not need to be fluorescent neither harmonic generator. The method was demonstrated in the optimization of pulses from a Kerr-lens modelocked Ti:sapphire laser using fluorescent and non-fluorescent samples.