Monoclinicβ-BaY₂F₈—a novel crystal simultaneously active for SRS and Ln³⁺-ion lasing

Abstract

This paper presents the first investigation of stimulated Raman scattering (SRS) in the monoclinic fluoride crystal β-BaY 2 F 8 , which is known as a promising host-material for trivalent lanthanide (Ln 3+ ) lasant ions. Picosecond laser excitation in the visible and near-IR spectral range at room temperature revealed the manifestation of nine SRS-promoting phonon modes, which are related to A g and B g vibrations of the crystal. Besides multi-phonon Stokes and anti-Stokes generation, we observed cross-cascaded χ (3) ↔ χ (3) processes involving different pairs of SRS-active phonons. A comparative estimation of the first Stokes steadystate Raman gain coefficients, both in the visible and near-IR region related to the most active SRS-phonon mode ω SRS1 ≈ 208 cm −1 of β-BaY 2 F 8 , was also performed. Furthermore, a brief review of the pioneering papers on laser action of Ln 3+ -ions doped in β-BaY 2 F 8 single crystals and other known SRS-active fluoride crystals is given in tabular form. Keywords: stimulated Raman scattering (SRS), monoclinic β-BaY 2 F 8 crystal, Raman four-wave mixing, χ (3) -nonlinear optical effects, many-phonon SRS, cascaded and cross-cascaded SRS