Synthesis of Supershort UV-Pulses Using Phase-Locked Raman Side-Band Generation

Abstract

We demonstrate a new technique of fs-pulse generation employing ultrafast modulation of a laser field phase by impulsively excited molecular rotational or vibrational motion with subsequent temporal compression. An ultrashort pump pulse at 800 nm performs impulsive excitation of a molecular gas in a hollow waveguide and a weak delayed probe pulse at 400 nm is scattered on the temporal oscillations of its dielectric index. The resulting sinusoidal phase modulation of the probe pulse allows pulse temporal compression using both positively and negatively dispersive elements. The potential of this new method is demonstrated by the generation of a periodic train of 5.5 fs pulses at 400 nm which are the shortest ever generated in the UV.