A novel short pulse generation technique based on the modulation of the optical phase by coherently prepared molecular vibrations will be discussed. In this method, an intense fs-pump pulse performs impulsive excitation of a Raman-active medium, and a delayed probe pulse is scattered on the produced temporal oscillations of the dielectric index, which leads, in the spectral domain, to the generation of multiple phase-locked Raman components. Due to the sinusoidal character of phase modulation imposed by the molecules on the probe field, its transformation into amplitude one (e. g. temporal compression) can be performed using both positive and negative GVD-elements. By exploiting this new regime of fs-stimulated Raman scattering, we were able to generate periodical sequences and single 3.8-fs pulses being to our knowledge the shortest pulses in the visible reported so far. The potential of this method for attosecond generation and its extension to the hard X-ray region to modulate X-ray diffraction in crystals by coherent optical phonons will be discussed.
Friedrich-Schiller Universität, Jena, Germany