Autocorrelation of femtosecond VUV pulses using multiphoton ionization

Abstract

We have developed an autocorrelator utilizing multiphoton ionization of rare gases as a nonlinear medium to evaluate the pulse width of a femtosecond Ti:Sapphire laser at 882 nm. The autocorrelation width of 171 fs (FWHM) was evaluated by the autocorrelator utilizing nine-photon ionization of Ar. By using the ninth-order correlation factor of 1.06, the actual pulse width of 161 fs (FWHM) was determined, which was consistent to that of 165 fs (FWHM) measured with a two-photon autocorrelator. The autocorrelation measurement utilizing the multiphoton ionization of Ar should be applied to vacuum ultraviolet (VUV) ultrashort pulses at 126 nm, since neutral Ar atoms will be ionized by two-photon absorption. This method has a potential to become a versatile autocorrelator that characterizes femtosecond laser pulse widths in the wide spectral range between IR and VUV.