Explanation of the competition between O- and E-wave induced stimulated Raman and supercontinuum in calcite under ultrafast laser excitation.

Key optical properties of calcite were measured to unravel the difference between stimulated Raman scattering (SRS) and self-phase modulation (SPM) for the supercontinuum (SC) for ordinary (O) wave and extraordinary (E) wave. These properties are group velocity dispersion, walk-off, spontaneous Raman spectra and cross section, optical 1086 cm(-1) phonon linewidth, nonlinear susceptibility (chi(3)), steady-state and transient SRS, and SC caused from SPM. These are investigated for O-waves and E-waves from a 2.7 cm thick calcite crystal. Using 390 fs pulses (similar to 0.8 mu J pulse energy) at 517 nm, the O-wave produced a stronger sharp SRS peak at 1086 cm(-1) and a weaker SC spectrum in the visible range than the E-wave. The salient difference found between the O-and E-waves for SRS and SPM in calcite is attributed to the larger Raman cross section and the size of nonlinear susceptibility (chi(3)) for O-waves as compared to E-waves. (C) 2020 Optical Society of America