Generation and characterization of spatially and temporally localized few-cycle optical wave packets

Direct experimental evidence of localized few-cycle wave packets with a characteristic spatiotemporal X shape is reported. These wave packets are also referred to as X pulses. For their generation, a Ti:sapphire laser beam was transformed into single and array-shaped Bessel-like beams by using broadband refractive and reflective thin-film axicons. Extremely small conical angles allow a reduction of the spatially induced group velocity dispersion and therefore enhance the contrast. Complete first and second order spatiotemporal autocorrelation maps of sub-10-fs localized wave packets are measured and are compared with numerical simulations. High-power X pulses open further prospects for advanced nonlinear optical experiments like the formation of spatiotemporal solitons.