Noncollinear frequency mixing and fourth-harmonic generation of oppositely chirped laser pulses

Abstract

Highly efficient fourth-harmonic generation of 60 µJ, 25 ps chirped (compressible down to 340 fs FWHM) Yb:KGW laser pulses was demonstrated experimentally utilizing noncollinear opposite chirp frequency mixing in Type I beta-barium borate (BBO) and lithium triborate (LBO) crystals as second-harmonic generators followed by collinear frequency doubling in another BBO crystal as a fourth-harmonic generator. Second-harmonic spectral narrowing by a factor over 100 and output UV pulse energy of 10 µJ were achieved.