Abstract

Wide frequency combs generation via stimulated Raman scattering (SRS) together with parametric four-wave coupling of Raman components, with equidistant lines in the frequency domain, has opened a new path of research in terms of ultrashort pulse synthesis and metrology [1]. In the most cases, parametric Raman generation is noncollinear due to the fulfillment of the phase matching condition of parametric four-wave mixing between the Raman radiation components [2]. However, noncollinear parametric Raman generation hasn’t yet found practical application in the synthesis of ultrashort light pulses, where collinear optical frequency comb generation is required. The conditions of low-threshold collinear wide frequency parametric Raman comb generation in crystals were theoretically studied in [3], showing the optimal SRS crystal length corresponding to highly efficient generation of an optical frequency comb from the 2^nd anti-Stokes to the 4^th Stokes Raman component. It has been also found that the optimal pump pulse duration is several times longer than the dephasing time of optical phonons and amounts tens picoseconds for the most of SRS crystals.

© 2015 IEEE