Optical activity of BSO crystals doped with Cr, Mn and Cu

Abstract The influence of both photochromic doping and photochromic transitions on the optical activity (OA) of undoped and doped Cr, Mn and Cu Bi 12 SiO 20 (BSO) crystals is studied. The results show that Cr strongly increases the optical rotatory power ρ of BSO up to 70–80% below 520 nm and decreases it (with about 40–50%) at the long-wavelength region. Mn decreases ρ of BSO: with about 3–4% in the range 480–700 nm, whereas Cu increases it with about 7–8% in the same range. The relation between OA and absorption is discussed. The results lead us to the assumption that Cr 3+ occupies Bi 3+ -tetrahedral (Td) positions, while Mn 4+/5+ occupies Si-tetrahedral positions. The opposite influence of Cu 2+ on ρ of BSO suggests that the Cu 2+ -ion preferentially replaces Si in BSO. In the co-doping cases, obviously, Al 3+ predominately displaces Cr 3+ from its Bi 3+ -Td M-sites. In the case of BSO:P, the results undoubtedly indicate that Cr 3+ displaces P 5+ .