Generation of subfemtosecond pulses by beating a femtosecond pulse with a Raman coherence adiabatically prepared in solid hydrogen

We show that the beating of a nanojoule femtosecond pulse with a Raman coherence adiabatically prepared by a pair of millijoule nanosecond pulses in solid hydrogen leads to an efficient generation of a triplet, doublet, or even singlet of subfemtosecond pulses. The energy conversion efficiency of the subfemtosecond pulse generation can be larger than unity due to the transfer of energy from the driving pulses.