All-solid-state laser system for the generation of tunable femtosecond light pulses in the vacuum UV down to 172.7 nm

We report what is to our knowledge the first generation of femtosecond light pulses in the wavelength range from 172.7 to 187 nm in an all- solid-state system operating at kilohertz repetition rate. Phase-matched sum frequency mixing in lithium triborate (LBO) between the fourth harmonic of a femtosecond Ti:sapphire regenerative amplifier and the idler pulses from a traveling wave optical parametric generator pumped by the same amplifier is used to approach these unprecedented short UV wavelengths. Estimations of the achieved pulse duration yield values below 200 fs in the whole vacuum UV tuning range. At 180 nm we measure single pulse energies as high as 50 nJ.