Dark conductivity, photoconductivity, and light-induced absorption in photorefractive sillenite crystals

Abstract

We measure the bulk and light-induced absorption as well as the dark- and photoconductivity in doped and undoped photorefractive Bi12TiO20 crystals and compare the results obtained using different techniques. From these data we compute the quantum efficiency for the photogeneration of charge carriers and the carriers mobility–lifetime product, and characterize the suitability of these crystals for holographic recording. A two-center model theory is shown to adequately describe absorption and photoconduction in these materials.

Photochromism, bleaching and photorefractive recording in undoped Bi12TiO20 crystals in the visible and near infrared wavelength range

“…The thermal relaxation of these filled shallow traps is rather slow so that the associated photochromic effect remains for some time even in the dark. The density of these shallow traps is usually much lower than that of deep ones so that they can be easily saturated [8]. In spite of their lower density, their darkening effect is rather pronounced probably because of a comparatively large effective photon cross section.…”

“…In spite of their lower density, their darkening effect is rather pronounced probably because of a comparatively large effective photon cross section. Darkening with 514.5 nm wavelength light, for example, is noticeable in nominally undoped BTO for as low an irradiance as a few lW/cm 2 [8].…”

“…From the two-center model theory [8,19] the total concentration of electrons N in the conduction band (CB) and of light-induced filled shallow traps (ST) N D2 À N þ D2 are respectively computed as…”

“…Bi 12 TiO 20 (BTO) is particularly interesting among sillenites because it exhibits the lowest (about 11°/mm at 514.5 nm wavelength) optical activity. Sillenites in general and BTO in particular show a relatively strong light absorption as well as a pronounced lightinduced absorption (photochromic) effect [4][5][6][7][8][9][10] in the visible wavelength range. Absorption is in general inconvenient for holographic recording because it reduces the level of light available for recording.…”

Growth and optical characterization of cerium and lead‐doped Bi12TiO20 sillenite single crystals

“…[11]. In that article, the authors state that the diffraction efficiency of BTO:Ce and BTO:Pb measured under similar conditions per unit crystal thickness using light with λ = 514.5 nm is, respectively, 80% and 65% less than that of undoped BTO.…”