Ultrashort pulse characterization by ultra-thin ZnO, GaN, and AlN crystals

Ultra-thin semiconductor crystals were investigated as nonlinear materials for second-harmonic generation. Nonlinear susceptibilities of sub-micrometer- thick ZnO, GaN, and AlN crystals were measured, and these crystals were used for sub-10-fs pulse measurement by a fringe-resolved autocorrelation method. We found that a one-cycle pulse could be characterized by using these ultra-thin-film crystals.