Highly efficient stimulated Raman scattering of picosecond pulses in KTiOPO4

High-efficiency picosecond stimulated Raman scattering (SRS) by phonon-polaritons has been observed in KTiOPO4 in a single pass through a 10mm long crystal. For pulses longer than 10ps, the SRS waves formed a symmetric pattern consisting of four distinct beams: SRS Stokes and anti-Stokes wavelengths originating both from the near-infrared pump and from the scattering of the second harmonic of the pump. At peak intensities above 10GW∕cm2 and pulse length of 1.5ps, the SRS character changes into what can be called “runaway” Raman scattering with efficiencies exceeding 50% and Raman gain spreading over 60THz.