20-fs pulse shaping with a 512-element phase-only liquid crystal modulator

We report pulse shaping experiments in the 20-fs range using a 512-element phase-only liquid crystal modulator array. The results demonstrate the potential for significantly improved spectral resolution compared to 128-element liquid crystal modulators previously used for pulse shaping. Furthermore, we show that subtle nonlinear spatial dispersion has a profound effect on replica pulses arising due to the pixellated nature of the liquid crystal modulator and may dramatically reduce their (already low) peak intensity.