Nanooptics and photonics

Photochromism of Bi12SiO 20 crystals doped with 
Cr, Mn and V ions

Panchenko T.V.1, Karpova L.M.2
1 Oles Honchar Dnipro National University, Faculty of Physics, Electronics and Computer Systems. 
Gagarina street, 72, Dnipro -49010, Ukraine. 
E-mail: email.of. corresponding_panchtv141@gmail.com
2 Ukrainian State University of Chemical Technology, Faculty of Mechanics, Gagarina street, 8, Dnipro-49010, Ukraine.

Bi12МO20 (ВМО, where М = Si, Ge, Ті) crystals have a unique set of practically useful properties (photorefractive, electrooptical and etc). They are successfully used in devices for recording, processing and storage of optical information [1]. BMOs have a cubic structure, but the main structural unit can be considered the molecular BiO7 ion.  
The results of an experimental study of the effect of Cr, Mn, and V ions on optical absorption and photochromic effect (PFC) in Вi12SiО20 crystals are presented. 
Undoped and doped with Cr, Mn and V ions BSO crystals (BSO:Cr), (BSO:Mn) (BSO:V), respectively,  were grown by the Czochralski method. The spectra of stationary α0(ν) and photoinduced optical absorption αPE(ν) were studied in the range ν = 4000- 28000 cm-1 at temperatures of 80 and 300 K.
	It has been established that the dominant optically active centers, which show themselves in the α0(ν) spectra of BSO: Cr, BSO: Mn, and BSO: V crystals are the 3d3-isoelectronic Сr3+, Мп4+, and V2+ ions in the Ві-nodes of the crystal lattice with a coordination number (c.n) 6. Electronic transition schemes and the crystal field strength Dq =1194, 1402, 1423 cm-1 for V2+, Сr3+, Мп4+, respectively, were determined.
It was shown that Cr and Mn ions enhance and V ions weaken the PCE with the appearance of characteristic changes in the PCE spectra of αPE(ν). Schemes of optical recharging of centers that are responsible for the PCE are proposed: Сґ2+ -е => Сг3' and Мп4++ е => Мп3+. 

1.	Gunter P., Huignard J. Photorefractive Materialsand Their Applications. Part 1. // Springer Science+Business Media, New York. – 2006.