Subfemtosecond pulse generation in a three-level system by molecular modulation

We show that subfemtosecond pulse train with large pulse spacing can be generated by using three correlated Raman generators between three Raman levels with strong molecular modulation to control the generation and propagation of the cascade stimulated Raman sidebands. For three Raman generators based on the fundamental rotational and vibrational Raman transitions (v=0,J=0<---->v=0,J=2<---->v=1,J=0<---->v=0,J=0) in molecular hydrogen, a train of subfemtosecond pulses with a pulse spacing of 379.9 fs and pulse width down to 0.26 fs can be generated.