We report the fourth‐harmonic generation of 1.5 ps, 1.053 &mgr;m glass laser pulses, where group velocity mismatch plays a significant role, at intensities up to 100 GW/cm2using newly developed crystal, cesium lithium borate (CsLiB6O10). Type‐I doubler and type‐I quadrupler were used in the fourth harmonic generation experimental scheme. Energy conversion efficiencies of 24% and 53% have been achieved for frequency quadrupling and doubling of the fundamental glass laser pulses, respectively. ©1996 American Institute of Physics.