Optica 4, 871–878 (2017)

The ability to perform single-shot intensity autocorrelation measurements and pump–probe spectroscopy in the vacuum-ultraviolet (VUV) region of the electromagnetic spectrum has been demonstrated by scientists in Hamburg, Germany. The team have tested their scheme at a wavelength of 162 nm using an ultrashort, fifth-harmonic pulse of a Ti:sapphire laser and captured an intensity autocorrelation trace that allowed the pulse duration to be determined as 18.4 ± 1 fs (full-width at half-maximum). The autocorrelation measurement was performed using an all-reflective set-up that consists of a silicon wedge mirror that acts as a beamsplitter to split the VUV pulse into two paths and then uses sets of spherical and plane mirrors to focus and route the counter-propagating split pulses so that they meet at a common focus in the vicinity of pulse of a noble gas jet of Kr or Xe. Non-resonant two-photon ionization of the gas serves as an autocorrelation signal and is captured by an ion-imaging time-of-flight spectrometer. A proof-of-principle pump–probe experiment using the 162 nm VUV pulses was also performed to study the dissociation dynamics of O2.