Generation of multicolor vacuum ultraviolet pulses through four-wave sum-frequency mixing in argon

We demonstrate efficient generation of multicolor vacuum ultraviolet pulses with excellent mode quality through χ⁽3⁾-based four-wave sum-frequency mixing and third-order harmonic generation of 400- and 267-nm femtosecond laser pulses in argon gas. The χ⁽3 ⁾-based nonlinear optical processes were optimized with appropriate control of gas pressure and group velocity delay between the driving pulses. Furthermore, the pulse breakup effects were observed for tightly focused ultraviolet pulses.