Stimulated Raman scattering in natural crystals of SrSO4, BaSO4 and PbSO4: High-order Stokes and anti-Stokes generation with single-wavelength UV, visible, and near-IR excitation, as well as cascaded up-conversion nonlinear χ (3)↔χ (3) lasing effects under dual-wavelength picosecond collinear coherent pumping

Abstract

Orthorhombic crystals of SrSO4, BaSO4, and PbSO4, known as natural crystals celestine, barite, and anglesite, were found to be attractive χ(3)-active nonlinear optical materials. High-order Stokes and anti-Stokes picosecond generation that spans almost two octaves has been recorded with single-wavelength laser excitation in the UV, visible, and near-IR ranges. All recorded Raman induced lasing components were identified and attributed to the SRS-promoting vibration modes of the studied crystals (ωSRS≈999 cm−1 for SrSO4,ωSRS≈985 cm−1 for BaSO4 and ωSRS≈977 cm−1 for PbSO4). Under dual-wavelength (λf1=1.06415 μm + λf2=0.53207 μm) collinear coherent picosecond pumping several new manifestations of cascaded χ(3)↔χ(3) nonlinear up-conversion lasing effects were observed in BaSO4 and SrSO4 crystals. We classify all three studied sulfate crystals as promising SRS-active materials for Raman laser frequency converters and as efficient χ(3)-crystals that efficiently generate Stokes and anti-Stokes frequency combs, which can enable experiments of ultra-short pulse syntheses.