Time resolved nonlinear spectroscopy at the band edge of 1D photonic crystals

Large refractive index changes have been measured at the band edge frequency of 1D photonic crystals (PCs). Results concerning both thin and thick samples of high and low refractive index contrasts, respectively, are presented. The very large value of the refractive index changes obtained at moderate pump powers thanks to the strong enhancement of the local intensity inside the PC opens the way to very small volume devices for optical signal processing. However, time resolved experiments demonstrate the photo-generation of high free carrier densities through two- or even three-photon absorptions, which are shown to be also strongly enhanced at the band edge of the PC. This drawback may most probably be circumvented by using lower pump intensities in PCs showing narrower resonances.