Comprehensive Study of Third-Order Nonlinear Tungstates: Relationship between Structural and Vibrational Properties in Raman Shifters

Although tungstates are now well known as laser Raman shifters, their physicochemical properties (especially the vibrational ones) were not often studied. We have carried out a comprehensive and systematic study of tungstate Raman spectra, thanks to which, structural and vibrational properties could be correlated. It was shown that the Raman scattering characteristics of these compounds are directed by simple physical chemistry parameters. They change logically with easy interpolation. The optimization of the search for tungstates as new efficient Raman shifters was realized through a figure of merit: a map where the Raman frequency is described versus a normalized parameter representative of the Raman gain.