Colour centres in LiNbO3LiNbO3:Fe and LiNbO3LiNbO3:Cu crystals irradiated by 12C ions

The present work is devoted to the investigation of optical absorption of pure and doped LiNbO3LiNbO3 (LN) single crystals in the spectral range 5000–32000cm-1 induced under influence of the 12C ions irradiation with energy 4.5 MeV/u   (MeV per nucleon) and a fluence 2×109cm-2 at room temperature. It was found that no remarkable absorption changes occur in pure and Mg-doped LN crystals, but in Fe- and Cu-doped ones. The induced additional absorption in LN:Fe crystals is attributed with Fe ions reducing Fe3+→Fe2+Fe3+→Fe2+ occurring simultaneously with hole centres formation O-O-, while only Cu2+→Cu+Cu2+→Cu+ reduction was observed in LN:Cu crystals.