Photorefractive properties ofBi4Ti3

Yue X

¹

,

Jingjun Xu

²

,

F. Mersch

³

et al.

Abstract

Three gratings are observed during holographic recording in Bi 4 Ti 3 O 12 : There is a primary photoinduced grating with fast response and a dephasing of /2 with respect to the light pattern. It is compensated for by a complementary charge grating with much slower response. The third grating identified by phase-shift experiments is an absorption grating. At an intensity of about 0.5 W/cm 2 , a peak refractive-index change of ⌬nϭ1.8ϫ10 Ϫ5 is achieved with a response time constant 1 ϭ40 ms. The mobility-lifetime product of the charges responsible for the primary grating is R1 ϭ7.0ϫ10 Ϫ12 cm 2 /V. The conductivity of the complementary charges is much smaller than that of the primary charges, which makes it possible to prolong the readout time of the recorded holographic grating considerably.

Specific Recording Kinetics as a General Property of Unconventional Photorefractive Media

“…Such a behavior is rather unusual for common (electro-optic) photorefractive materials. In case of appearance these kinetics is frequently attributed to compensating gratings [20]. We emphasize that for the particular case of SNP it was proven that this explanation was not consistent with the experimental findings [21].…”

“…The strengths of the presented model are its generality and the consistent description of the kinetics with only three free parameters. We emphasize that the assumption of an optical two-state system shall be applicable to a lot of systems including photo- [11], CdF 2 :Ga [26], AlGaAs:Te [27], CdZnTe:Cl [17], and the ferroelectric Bi 4 Ti 3 O 12 [20]. A limiting assumption of the presented model is the linear relation between the refractive-index change n li and the population fraction p B .…”

Evaluation of Non-Diagonal Components of the Pockels Tensor for Photorefractive Sn2P2S6 Crystal

“…Most part of photorefractive crystals have orthorhombic, trigonal, or higher symmetry, but several monoclinic photorefractives are also known. For example, tin hypothiodiphosphate (Sn 2 P 2 S 6 , SPS) [1] and bismuth titanate [2] are monoclinic. The low symmetry of these crystals results in the necessity to use particular Cartesian frames to describe their dielectric, optical, and electro-optical properties that do not coincide with the standard crystallographic frame.…”