Application of adaptive feedback loop for ultra-violet femtosecond pulse shaper control.

We apply an adaptive feedback loop to control a ultra-violet (UV) femtosecond pulse shaping apparatus. The adaptive feedback control is implemented by a continuous parameter genetic algorithm. We use the adaptive shaper to compensate for the pulse chirp. The genetic algorithm produces a pulse with a width of 115 fs, identical to that of the transformlimited pulse. We then apply the adaptive shaper to the Stokes pulse in a femtosecond coherent anti-Stokes Raman scattering (CARS) experiment on dipicolinic acid solution. The algorithm maximizes the first CARS beat signal at the probe pulse delay of 650 fs. We confirm that a transformlimited Stokes pulse achieves the best detection sensitivity.