Phase- and group-matched nonlinear interactions mediated by multiple filamentation in Kerr media

Laser-pulse filamentation in Kerr media induced by a strongly elliptic input beam leads to breakup into a periodic array of filaments. In the plane of the filament array we observe strong Stokes and anti-Stokes emission at large angles. For 1 ps input pulses the measured angles are found to support two different phase-matching configurations: one nontransversally phase matched and the other perfectly phase matched. Shorter 200 fs pulses give rise to group-velocity-matched Raman conversion.