Investigation of the fine structure of inhomogeneously broadened absorption bands of the $Nb^{3+}$ ion in glass by the selective excitation method

The selective laser excitation method was used to reveal the fine structure of the inhomogeneously broadened ${}^4I_{9/2}\to{}^2G_{7/2}$ and ${}^4G_{5/2}$ absorption bands and diagrams showing the Stark components of the states ${}^2G_{7/2}$ and ${}^4G_{5/2}$ were plotted by recording the luminescence due to the ${}^4F_{3/2}\to{}^4I_{9/2}$ and ${}^4I_{11/2}$ transitions. An overall diagram of the positions of the Stark levels of the ${}2G_{7/2}$; ${}4G_{7/2}$; ${}^4F_{3/2}$; ${}^4I_{9/2}$; ${}^4I_{11/2}$ states of a continuous set of optical $Nb^{3+}$ centers in silicate glass was obtained for the first time.