Selenium molecules and their possible role in deep emission from glasses doped with selenide nanocrystals

We report the observation of Raman scattering from a vibration mode with frequency of 320 cm−1 and its higher-order harmonics in silicate glasses doped with selenide semiconductor nanocrystals such as CdSe and ZnSe. Comparison with Raman spectra of glasses and alkali halides doped with Se suggests that these modes are caused by the presence of selenium molecules in the glasses. When excited in the blue and green by an Ar+ laser, glasses containing Se only are found to emit strong near-infrared luminescence whose peak and line shape are very similar to the so-called ‘‘deep emission’’ observed frequently from selenide-doped glasses. Possible effects of Se molecules on the linear and nonlinear optical properties of glasses containing selenide nanocrystals are discussed.