Direct In Situ Measurement of an Ultrashort Pulse Using an Optical Hologram

Abstract

The dipole response of helium exposed to attosecond extreme ultraviolet (EUV) pulses and a femtosecond near-infrared (NIR) laser field is investigated. The optical interference between the EUV pulse and nonlinear wave-mixing signals leads to fringes in the transmitted spectrum above the single ionization threshold. Perturbation theory suggests that such fringes record the self-convolution of complex-valued NIR pulse in the frequency domain, allowing direct characterization of a broadband optical pulse without the need of reconstruction algorithms. We apply this in situ interferometric scheme to diagnose a few-cycle laser pulse.