Abstract

Stimulated Raman scattering is an efficient way to shift the frequency of the available laser sources. When the light pulse duration decreases and approaches the transverse relaxation time of the Raman medium, the highly transient interaction reduces the efficiency of the scattering process.¹ At the same time, competitive nonlinear processes (selfphase modulation, multiphoton ionisation) limit the conversion into Stokes lines. Nevertheless, by optimised focusing, efficient Raman scattering of ultraviolet femtosecond light pulses was already demonstrated.² However, the pulse duration in these experiments was not measured and only a rough estimation for the pulsewidth could be done from the spectrum data. Here we report on Raman scattering of visible femtosecond pulses and the first to our knowledge, generation of light pulses below 100 fs using this technique. We show that by proper balancing of the input intensity high efficiency of the Raman scattering for femtosecond light pulses can be achieved. In addition, the Raman-shifted pulses are efficiently compressed 6.5 times as compared to the pump pulse duration.

© 1994 IEEE