Cerium Doped Strontium Barium Niobate Research Articles

Optical induction of non-diffracting discrete photonic lattice

The triangle lattices was optically induced in an externally biased cerium doped strontium barium niobate (SBN) photorefractive crystal using a mask with three holes or six holes, respectively. Numerically, the transmittance function of the amplitude mask and its Fourier-transform function were given out instead of treating each hole as a simple point source. Experimentally, the differences between the two lattices were analyze by phase distribution, far-field diffraction pattern, Brillouin-zone spectroscopy. And the three-dimensional (3D) images by computer simulation are also used to study their differences. In addition, the anisotropy lattices are presented by designing the amplitude mask properly.

2D infrared self-focusing in bulk photorefractive SBN

We experimentally demonstrate the possibility of photorefractive 2D self-focusing in bulk Cerium doped Strontium Barium Niobate (SBN:Ce) directly at telecommunications wavelengths (1.06 μm and 1.55 μm). Although the electro-optic coefficient of SBN is smaller at infrared wavelengths, 2D infrared self-trapping is observed and analyzed versus different parameters such as the laser beam intensity, the external applied electric field and time.

Three-dimensional optically induced reconfigurable photorefractive nonlinear photonic lattices

We experimentally investigate the formation of reconfigurable three-dimensional (3D) nonlinear photonic lattices in an externally biased cerium doped strontium barium niobate photorefractive crystal by a spatial light modulator-assisted versatile simplified single step optical induction approach. The analysis of the generated 3D nonlinear photonic lattices by plane wave guiding, momentum space spectroscopy, and far field diffraction pattern imaging is presented, which points to the embedded potential of these 3D structures as reconfigurable platform to investigate advanced nonlinear light-matter interaction in periodic structures.

Substrate Induced Pre-tilt in Hybrid Liquid Crystal/Inorganic Photorefractives

We report on the photorefractive properties of nematic liquid crystals sandwiched between windows of cerium doped strontium barium niobate (Ce:SBN). Unlike simple glass substrates, the Ce:SBN induces molecular pre-tilts that generate electric dipole moments in the liquid crystal through the flexoelectric effect. This enables the liquid crystal to become sensitive to the sign of the space-charge field and leads to an increase in the optical amplification when the cell thickness is decreased.

Dispersion of the electro-optic properties of cerium-doped Sr0.61Ba0.39Nb2O6

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.

Determination of large nematic pre-tilt in liquid crystal cells with mechanically rubbed photorefractive Ce:SBN windows

We report on the determination of liquid crystal pre-tilt inside cells fabricated using single crystal birefringent and dichroic windows of cerium doped strontium barium niobate. We show that the average pre-tilt is significantly affected by the crystalline windows, leading to much larger values than those obtained with glass windows using identical fabrication methods. The same technique can be used to determine pre-tilts as large as 40 degrees, which is significantly larger than normally measurable using the cell rotation method.

Angular and wavelength selectivity of parasitic holograms in cerium doped strontium barium niobate

The angular and wavelength selectivity of noise gratings in doped strontium barium niobate crystals for samples with two different thicknesses are investigated. We found that an offset in the optimum reconstruction angle with respect to the recording geometry occurs as a function of the thickness. This is a consequence of the unidirectional amplification. Thus the scattering intensity for the thinner sample is considerably lowered at the very recording conditions. We analyze the experimental results in terms of the kinematic theory of diffraction.

Thermal Lensing and Optical Bistability in Ferroelectrics

In a recently developed theory of thermal lensing by ferroelectrics under laser illumination, the sample temperature as a function of radius and time was expressed as an integral. It is now shown that this integral can be approximated by known functions in a form which is accurate to within 1% for practical experimental situations. The theory is extended to explain asymmetric thermal focusing by BNN (barium sodium niobate, Ba2NaNb5O15). The presence of optical bistability in PMN (lead magnesium niobate, Pb(Mg1/3Nb2/3)O3), and PLZT (lanthanum doped lead zirconium titanate, Pb(Zr1-xTix)O3:La) and its absence in BNN and Ce:SBN (cerium doped strontium barium niobate, Ce3+:SrxBa1-xNb2O6) is explained by the presence or absence of Fabry-Pérot resonance. Possible sustained periodic relaxation oscillations are discussed.

Temperature study of photoinduced wide-angle scattering in cerium-doped strontium barium niobate

The photoinduced polarization-isotropic scattering in strontium barium niobate (SBN) doped with 0.66-mol. % cerium has been studied over a wide temperature range including the region of the relaxor phase transition. The temperature evolution of the scattering pattern has been examined with respect to changes in the domain structure and of optical parameters of the crystal resulting from the phase transition from a ferroelectric state to a paraelectric state. The scattering properties at temperatures above the ferroeletric phase are connected to the relaxor behavior of SBN. We found that a transition temperature TC can be defined from the temperature evolution of the scattering pattern much more precisely than with conventional methods such as frequency-dependent measurements of the dielectric susceptibility.

Proposal and demonstration of cached holographic 3D display system using photorefractive crystals

We demonstrate a new 3D display system with photorefractive crystals named “cached holographic 3D display”. This new system is based on a combination of computer-generated holographic display technology and holographic storage technology, and has the potential to become a universal way of viewing naturally looking 3D images. We use cerium doped strontium barium niobate crystals as a temporary storage medium in the system. The crystals include striations, which degrade the display resolution.

Mechanisms for optical oscillations in ferroelectric films

Abstract Under steady laser illumination, aperiodic spatio-temporal oscillations are observed in the light transmitted and reflected by parallel-sided samples of the ferroelectrics PMN (lead magnesium niobate, Pb(Mg 1/3 Nb 2/3 )O 3 ), PLZT (lanthanum doped lead zirconium titanate, Pb(Zr 1– x Ti x )O 3 :La), BNN (barium sodium niobate, Ba 2 NaNb 5 O 15 ) and Ce:SBN (cerium doped strontium barium niobate, Ce 3+ :Sr x Ba 1– x Nb 2 O 6 ). There are two distinct mechanisms for such oscillations, namely (1) unistable thermal focusing oscillations, which occur in BNN and Ce:SBN and (2) bistable or multistable Fabry-Perot switching oscillations, as observed in PMN and PLZT. The two types of oscillation have characteristic time scales differing by several orders of magnitude. We derive temperature profiles as a function of incident laser power, beamwidth and sample thickness, which quantitatively predict the spatio-temporal characteristics of the transmitted beam patterns.

Charge-transport parameters of photorefractive strontium-barium niobate crystals doped with cerium

A complete set of charge-transport parameters of photorefractive cerium-doped strontium-barium niobate crystals is determined: the concentrations of filled and empty traps, the photon-absorption cross section, the quantum efficiency for excitation of an electron upon absorption of a photon, the recombination coefficient, and the charge-carrier mobility. These parameters are obtained evaluating optical absorption, conductivity, non-steady-state photocurrents, neutron-activation analysis, and x-ray photoelectron spectra. The effective absorption radius of the filled electron traps is small and the effective trapping radius is large compared with the ionic radii. Before recombination with deep levels the excited electrons are trapped several times by shallow levels. A detailed description of the charge transport is obtained, and the properties of optimized crystals are deduced.

Wavelength-multiplexed holographic data storage by use of reflection geometry with a cerium-doped strontium barium niobate single-crystal structure and a tunable laser diode

We present wavelength-multiplexed holographic recording forhigh-density, high-speed data storage using reflection geometry with ahigh-sensitivity cerium-doped strontium barium niobate single-crystalstructure and second-harmonic generated light from a compact andconvenient wavelength-tunable laser diode. We have recorded andreconstructed wavelength-multiplexed holograms by using wavelengths0.053-nm apart. The theoretical wavelength selectivity of thehologram with the linewidth of the light source taken intoconsideration agrees well with the experimental wavelength selectivity.

Activation of cerium-doped strontium-barium niobate for infrared holographic recording

Homogeneous illumination of Sr 1− x Ba x Nb 2O 6:Ce (0.25 ≤ x ≤ 0.75; SBN) crystals with a green light pulse allows subsequent recording of a holographic grating with infrared light pulses. The grating can be read nondestructively with infrared light and can be erased by illumination with green light. The results indicate that the charge transport in Sr 1− x Ba x Nb 2O 6:Ce must be described by a two-level model.

Piezoelectric properties and equivalent circuits of ferroelectric relaxor single crystals

Temperature dependent piezoelectric properties of ferroelectric relaxor single crystals, particularly the cerium-doped strontium barium niobate compositions (SBN60: Ce), were investigated by resonance and anti-resonance technique. Characteristic resonant frequencies (fr−fa, fs−fp, and fm−fn) were studied using equivalent circuit simulation. Piezoelectric resonance in a relaxor resonator persists into temperatures much higher than Tm (the temperature at which dielectric constant, κ, has a maximum at 1 kHz) in comparison with the normal ferroelectrics such as TGS. The parameters in an equivalent circuit, however, are phenomenally different from a normal resonator like a TGS, near and above the transition temperature region. The significance and understanding of the piezoelectric resonance characteristics in ferroelectric relaxor are discussed.

Ion-beam manipulation of the photorefractive properties of strontium barium niobate planar waveguides

Photorefractive planar waveguides have been fabricated in cerium-doped strontium barium niobate (Sr(x)Ba(1-x)Nb(2)O(6), SBN) single crystals by ion-beam implantation. The losses measured were as low as 0.1 and 7.0 dB cm(-1) for the TM and the TE modes, respectively. Subsequent two-beam-coupling experiments performed on the waveguides showed that, unlike for BaTiO(3) and KNbO(3) waveguides formed by ion-beam implantation, the two-beam-coupling gain direction did not reverse. Also, the response time had been reduced by 2 orders of magnitude.

Wavelength-Multiplexed Holographic Recording in Cerium Doped Strontium Barium Niobate by Using Tunable Laser Diode

Seven multiplexed two-dimensional images are recorded and reconstructed by wavelength-multiplexed holographic recording in a cerium (Ce) doped strontium barium niobate (SBN) single crystal by using a tunable laser diode. Analytical formulas for calculating diffraction efficiency are derived by using modified coupled wave equations. Wavelength and angle selectivities of the holograms, which indicate the crosstalk between the multiplexed holograms, agree well with theoretical selectivities derived from the analysis. The theoretical and experimental results suggest that 300 to 400 holograms can be multiplexed.

Observation of ferroelectric 180° domains by microphotometry of holographic gratings

A new holographic observation technique for 180° domains is demonstrated with a cerium-doped strontium barium niobate sample containing two antiparallel ferroelectric domains. The method relies on the fact that the phase shift of holographically written refractive-index gratings is +π/2 or -π/2 with respect to the initial light interference pattern depending on the orientation of the domains. As a consequence, readout of these gratings creates at the exit face of the sample new interference patterns shifted by 0 or π with respect to the initial one. These patterns, providing an image of the domain structure, are observed by microscope.

Picosecond Phase Conjugation and Two-wave Coupling in Strontium Barium Niobate

Abstract Picosecond phase conjugation and two-wave coupling in cerium-doped strontium barium niobate at 778 nm were studied. The phase conjugation reflectivity at 778 nm was measured to be R pc = 58%. It is close to that pumped by a continuous-wave pump source. The temporal width t pc and spectral width δγpc of the phase conjugate pulse were measured to be the same as that of the pump pulse. The intensity coupling gain of two-wave coupling as a function of time delay τD between two beams was also studied.

Pyroelectrically induced photorefractive effect in Sr_061Ba_039Nb_2O_6:Ce

Photorefractive properties of a cerium-doped strontium barium niobate single crystal (Sr(0.61)Ba(0.39)Nb(2)O(6)) are investigated with Q-switched light pulses (wavelength 532 nm). Pyroelectric fields are the dominant charge driving force and significantly enhance light-induced refractive-index changes.