Ce-doped SBN Research Articles

Structure and electric properties of cerium substituted SrBi1.8Ce0.2Nb2O9 and SrBi1.8Ce0.2Ta2O9 ceramics

SrBi1.8Ce0.2Nb2O9 (SBCN) and SrBi1.8Ce0.2Ta2O9 (SBCT) powders were prepared via solid-state reaction method. X-ray diffraction analysis reveals that the SBCN and SBCT powders have the single phase orthorhom-bic Aurivillius structure at room temperature. The contribution of Raman scattering and FTIR spectroscopy of these samples were relatively smooth and resemble each other. The calcined powders were uniaxially pressed and sintered at 1250?C for 8 h to obtaine dense ceramics. Dielectric constant, loss tangent and AC conductivity of the sintered Ce-doped SrBi2Nb2O9 and SrBi2Ta2O9 ceramics were measured by LCR meter. The Ce-doped SBN (SBCN) ceramics have a higher Curie temperature (TC) and dielectric constant at TC (380?C and ?? ~3510) compared to the Ce-doped SBT (SBCT) ceramics (330?C and ?? ~115) when measured at 100Hz. However, the Ce-doped SBT (SBCT) ceramics have lower conductivity and dielectric loss.

Study on the absorption characteristics and birefringence of Ce-doped SBN

Cerium-doped Sr 0.60 Ba 0.40 Nb 2 O 6 (SBN:60) crystals were obtained by Czochralski method. Optical transmission spectra were measured and the absorption coefficients were calculated in the visible range. The results showed that Ce-doped crystals were transparent for wavelengths more than 650 nm and the fundamental absorption edge shifted towards the longer wavelength direction with increasing Ce concentrations. In addition, the birefringence of crystals were investigated based on the theory of interference between extraordinarily and ordinarily polarized light, and the birefringence values were determined in the long wavelength region. As a result, the birefringence becomes larger by doping of SBN crystals with cerium.

Optical recording of reversed domains in a Ce-doped SBN:75 crystal for bit-oriented three-dimensional optical memory

We developed a bit-oriented three-dimensional recording with a Ce-doped Sr0.75Ba0.25Nb2O6 (SBN:75) crystal. The ferroelectric polarization was reversed by a focused laser beam in a crystal with a temperature of 38 °C to form bit data. The recorded domain was stable at 15 °C. The data were read as the refractive-index change induced by spontaneous polarization through the Pockels effect. We wrote a single datum in SBN:75 crystal with ferroelectric-domain reversal and observed the domain image with a phase-contrast microscope. Numerical calculations to estimate the domain image were also performed. The observed results were in good agreement with the numerical expectations.

Electrical fixing of 1000 angle-multiplexed holograms in SBN:75

We have demonstrated electrical fixing of 1000 angle-multiplexed holograms in a 1-cm(3)volume Ce-doped SBN:75 crystal. A revealing procedure yielded an average diffraction efficiency of 0.005% for each hologram, with approximately 20% variation. The erasure resistance of the fixed gratings was verified.

Trapping the grating envelope in bulk photorefractive media

We introduce the concept of traveling grating envelopes to study the erasure dynamics in bulk photorefractive media. This new technique provides considerable physical insight into the observed photorefractive transients. We propose and demonstrate experimentally, in a Ce-doped SBN:60 crystal, two novel ways of extending the grating lifetime by trapping the grating envelope inside the medium. The incident beam ratio and the readout geometry have the largest effect on how long the grating can be read out.

Growth and photoreactive properties of a- and c-axis cerium-doped strontium barium niobate single-crystal fibers

The authors report on the photorefractive properties of cerium-doped strontium barium niobate (Ce:SBN60) single-crystal fibers grown by the laser-heated pedestal growth method. Single-crystal fibers, 250 mu m in diameter, were successfully grown along both the a- and c-axes. The diffraction efficiency and grating formation time results for each fiber in two beam coupling experiments are compared, with emphasis on their crystal orientation and relevant figure of merit. It is found that the hologram efficiency of the a-axis fiber is larger than that of the c-axis fiber and that its grating formation time is faster. The results suggest that Ce-doped SBN single-crystal fiber grown along the a-axis is a promising candidates for holographic storage, parallel data processing, and phase-conjugation mirrors. >

Photorefractive gain and response time of Cr-doped strontium barium niobate

We present experimental results on the photorefractive two-beam coupling constant and response time of two Cr-doped strontium barium niobate crystals with different dopant concentrations. Both showed significantly faster response times over Ce-doped SBN:60, but with corresponding decreases in their coupling constants.

Photorefractive properties of Ce- and Ca-doped Sr0.6Ba0.4Nb2O6

We present the results of experimental study of the absorption coefficient, two-beam photorefractive coupling constant, and photorefractive response time of a doubly Ce- and Ca-doped Sr0.6Ba0.4Nb2O6. This crystal displays enhanced photorefractive response at near infrared wavelengths when compared to Ce-doped SBN:60. The temperature dependence of the coupling constant over the range from −30 to 40 °C has also been studied.

High-sensitivity holographic storage in Ce-doped strontium-barium niobate at 632.8nm

We report the high-sensitivity holographic storage in Ce-doped SBN with a low power CW He-Ne laser. A maximum index change Δnmax=1.07×10-4, a photorefractive sensitivity S=7.9×10-4cm2/J, and a maximum diffraction efficiency η=78% were obtained. The optical readout characteristics of holograms recorded by the sample were also studied.