Stimulated Raman Scattering in Melilite‐Type Crystals Ca2MgSi2O7 and Ca2Ga2SiO7

χ(3)‐nonlinear optical interactions in two melilite‐type stimulated Raman scattering (SRS)‐active non‐centrosymmetric crystals, Ca2MgSi2O7 and Ca2Ga2SiO7, formerly known as Nd3+‐laser media, are presented. Under picosecond pumping at 1.064 and 0.532 µm cascaded and cross‐cascaded effects occur in these tetragonal silicates. Besides the SRS‐promoting phonon modes with energy of ωSRS1 ≈ 908 cm−1 and ωSRS2 ≈ 668 cm−1 for Ca2MgSi2O7, and ωSRS1 ≈ 720 cm−1 and ωSRS2 ≈ 550 cm−1 for Ca2Ga2SiO7, respectively, combined phonon modes are observed. For Ca2MgSi2O7 new data in a broad wavelength range of refractive indices and their dispersion are given as well. The observed χ(3)‐nonlinear properties expand the functionality of the studied silicates and foreshadow their use in self‐frequency Raman laser converters (self‐SRS lasers)

The luminescence of the scheelite NaBi(MoO4)2

The luminescent properties of the scheelite NaBi(MoO4)2 are reported. Below 50 K an efficient, red emission occurs. The results agree with those for other bismuth molybdates. The decay measurements indicate an energy level structure of the emitting state which is very similar to that in PbMoO4. The distribution of the Na+ and Bi3+ ions is probably short-range ordered

Structural investigations of the tetraborates MB4O7 M Pb, Sr, Ba

The crystal structures of the tetraborates MB4O7 were investigated at room temperature for M Sr, Pb, Ba and at 100 K for M Pb, Ba. The influence of the lone electron pair of Pb2 in PbB4O7 can be studied by comparing the isostructural compounds PbB4O7 and SrB4O7. The lone pair shows a clear displacement of the lead atom which increases upon cooling. In contrast with the Sr and Pb compounds, BaB4O7 crystallizes in a centrosymmetric structure. However, this structure seems to be on the border of stability, as we find strong internal stres

Whispering gallery resonator from lithium tetraborate for nonlinear optics

For second-order nonlinear-optical processes in the ultraviolet, appropriate materials with a sufficiently large band-gap typically exhibit smaller nonlinear coefficients than materials with comparably smaller band-gap. Whispering gallery resonators, with their outstanding quality factors, provide field enhancement and can compensate for these small coefficients. We report on the successful fabrication of a whispering gallery resonator made of lithium tetraborate, a suitable material for ultraviolet applications with a small nonlinear coefficient of d31 = 0.073 pm/V. Quality factors of the order of 108 are observed from the ultraviolet to the near-infrared spectrum. The inferred absorption coefficients of lithium tetraborate are below 0.2 m-1 in the visible and near-infrared. Continuous-wave second harmonic generation from 490 nm light to 245 nm is observed with conversion efficiencies up to 2.2 %