Conical light scattering is uncovered in poly- and mono-domain, nominally pure and
Eu-doped strontium barium niobate (SBN) crystals over a wide temperature regime. The
appearance of two scattering cones, a scattering line and a corona is observed and can be
explained comprehensively within the Ewald sphere concept. Photorefraction, scattering
from domain boundaries or from growth striations can be excluded from explaining the
origin of the scattering. It is shown that the temperature-persistent scattering process is
related to a growth-induced seeding rod, i.e. a composition inhomogeneity primarily
localized at the centre of the SBN sample. The rod is directed parallel to the
c
axis and yields a refractive-index inhomogeneity with spatial frequencies on the micro-scale.
Iron-doped lithium-tantalate samples with different compositions ranging from the congruently melting to the stoichiometric one are analyzed by anisotropic holographic scattering. The temperature dependence of the birefringence yields information on the composition of the crystals.
The product of the linear electro-optic coefficient with the electron-hole competition factor r33ζ is determined as a function of the wavelength together with the photorefractive trap density Neff in cerium-doped strontium barium niobate. The photorefractive method of photoinduced light scattering is applied. A pronounced increase of r33 by more than a factor of 2 is self-evident in the blue-green spectral range, which is described by a theoretical approach based on the combination of the Sellmeier formulation and the polarization tensor concept. By this further important material parameters are estimated, such as the strength and frequency of the average dipole oscillator characterizing the optical interband transfer.
Stationary and dynamic properties of photo-induced light scattering (PILS) have been
studied as a function of the photorefractive crystal thickness. A mono-exponential growth
of the scattering amplification coefficient as well as a deceleration of the scattering
recording dynamics is found with increasing crystal thickness. The experimental data
set is analyzed by considering scattering centers located (i) in the crystal bulk
or (ii) near to the crystal surface. By comparing experimental and theoretical
results we can conclude that the major contribution to the output scattering signal
originates from a thin crystal region frontier to the surface of light incidence
(near-surface). The deceleration of the scattering dynamics is interpreted as the result
of the competition between differently recorded noisy photorefractive gratings.
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