Direct near infrared photorefractive recording and pre-exposure controlled hole-electron competition with enhanced recording in undoped Bi12TiO20

We report the direct recording of electron-based photorefractive hologram in nominally undoped Bi12TiO20 crystals using 780 nm wavelength light without pre-exposure or any kind of previous processing. A lower intensity absorption grating is also detected. Pre-exposure with shorter wavelength produces an extended lifetime hole-based complementary grating on another photoactive center level and leads to enhanced recording.