Synthesis of sub 6 fs pulses in the UV using phase-locked Raman side-band generation

Summary form only given. The shortest presently available pulses in the UV (near 400 nm), generated by the traditional technique of SPM with subsequent group-delay dispersion compensation, have a duration of 8 fs. In this paper, we demonstrate an alternative approach resulting in even shorter pulses. The idea is to employ, instead of the nonlinear spectral broadening mechanism, a linear one which generally takes place when an electromagnetic wave propagates in an optical medium with temporally modulated dielectric parameters. The temporal modulation can be created, for example, by coherent excitation of molecular vibrational motion. By scattering a second, relatively weak pulse on the temporal grating one can generate Raman side-band lines free from nonlinear effects. In our experiments we used a Ti:sapphire chirped pulse amplification laser system.