Raman spectroscopy and the origin of electrooptical Kerr phenomenon in niobium alkali-silicate glasses

It is shown that magnitudes of the Kerr coefficient and permittivity of 19Na2O–11K2O–2B2O3–2CdO–(66−x)SiO2–xNb2O5 glasses, where 0<x<37, correlate with the content of the Na2O·Nb2O5 groupings, with that content being estimated by Raman scattering data. This allows assigning to these groupings, or to other structural entities containing such groupings (for example, crystal motifs), the responsibility for high-polarizability and Kerr sensitivity of the glasses.