Bismuth Silicon Oxide Crystal Research Articles

Nonlinearity of the photorefractive response upon two-beam interaction in a bismuth silicon oxide crystal in an alternating electric field

Nonlinearity of the photorefractive response is studied experimentally and theoretically upon two-beam interaction of light waves in a bismuth silicate crystal placed in an external meander electric field. The experimental data are shown to be in good agreement with a model, taking into account the influence of the second harmonic of the space-charge field on a photorefractive grating. The concentration of acceptors in a crystal and a product of the mobility of charge carriers by their recombination time are estimated from a comparison of the experimental and calculated data.

Single crystals of bismuth silicon oxide grown by the czochralski technique and their characterisation

Single crystals of Bi12SiO20 were grown by the Czochralski technique. The critical diameter and the critical rate of rotation were calculated. Suitable polishing and etching solutions were determined. X-Ray measurements were performed on powdered samples to obtain the lattice parameters. The optical properties of the bismuth silicon oxide single crystals were investigated. The obtained results are discussed and compared with published data.

Edge enhancement by use of moving gratings in a bismuth silicon oxide crystal and its application to optical correlation

The technique of moving gratings in a photorefractive crystal is applied to the edge enhancement of objects and edge-enhanced optical correlation. The nonlinear dependence of the optimum fringe velocity on the fringe modulation and the variation of the enhancement of the diffraction efficiency with fringe modulation at a fixed fringe velocity appropriate to high fringe modulations are experimentally investigated. It is shown that the diffraction at high fringe modulations, which corresponds to the high-spatial-frequency components of the Fourier spectrum, is enhanced by a factor of approximately 3.7, whereas the diffraction at low fringe modulations is suppressed by a factor of 0.6. The proposed technique has the advantages of real-time enhancement, arbitrary selection of the spatial frequency to be enhanced, and improved stability of the output. Experimental results of the edge enhancement of objects and edge-enhanced correlation are presented.

A broadband antireflection coating for enhanced holographic recording and readout in bismuth silicon oxide

We demonstrate a high-quality double-layer antireflection coating for high index (n=2.61 at 514 nm) photorefractive and electro-optic bismuth silicon oxide (Bi12SiO20) crystals. The antireflection coating comprises two electron-beam-deposited quarter-wave dielectric layers of MgF2 and ZrO2, and increases the beam throughput by as much as 20% per interface at normal incidence. For holographic recording applications, the antireflection coating eliminates multiple internal reflections that produce extraneous gratings. The combination of these two factors significantly increases the diffraction efficiency and the two-beam coupling gain. Key characteristics of the double-layer coating include a broadband minimum that encompasses typical write and read wavelengths for Bi12SiO20 with normal-incidence reflectivities of less than 0.2% at 514 nm and 1% at 633 nm, respectively, and a forgiving angular dispersion for both TE and TM polarized waves with reflectivities of less than 2% for angles of incidence up to 45°.

Synchrotron X-ray topography of bismuth silicon oxide crystals

The generation and distribution of growth defects in Czochralski-grown bismuth silicon oxide (Bi12SiO20) crystals have been studied by synchrotron X-ray topography. The relationship of the paths of grown-in dislocations with the shape of the crystal-melt interface is also reported.

Visualization of a Phase Object by Two-Wave Coupling in a Photorefractive Bismuth Silicon Oxide Crystal

We propose a method to visualize a phase object using a locally-controllable image amplification scheme we developed earlier which is based on two-wave coupling in a bismuth silicon oxide (Bi12SiO20, or BSO) crystal. In this method the BSO crystal is used as a phase plate in the configuration of Zernike’s phase contrast imaging system. The principle of the phase-visualization with two-wave coupling is presented. An experimental result to verify the proposed method is shown.

Phase-shifting real-time holographic interferometry that uses bismuth silicon oxide crystals

A bismuth silicon oxide crystal is used in the diffusion regime as a dynamic recording medium in a real-time holographic interferometer based on anisotropic self-diffraction. This device is connected with an interferogram-analysis method that uses the phase-shifting technique for quantitative measurement of diffusive-reflecting object deformations. In addition to the usual error sources in phase shifting, the temporal interferogram erasure is studied and is found weakly perturbative for the measured phase. It is shown that quantitative measurements are possible for low-intensity object beams (8 µW/cm(2)) and a large observed area. Apractical situation of defect monitoring in a composite structure is presented.

Low-temperature photochromic response of phosphorus-doped bismuth silicon oxide

Phosphorus is one of several dopants that electronically compensate the native deep donor responsible for the yellow coloration observed in bismuth silicon oxide (BSO). Low-temperature optical absorption measurements of a series of Czochralski-grown P-doped BSO crystals show that ∼0.1–0.15 at. % P is needed in the sample to fully remove the yellow coloration. The absorption cutoff in the fully compensated P-doped sample was at 3.2 eV while compensated Al- and Ga-doped samples cutoff at 3.35 eV. Excitation at 10–15 K with near band-edge light produces photochromic absorption bands. In the lightly-doped (partially bleached) samples these bands were identical to those observed in undoped BSO. In the fully bleached sample a new spectrum was observed. Its major contribution was a band centered near 1.8 eV with a weaker absorption in the blue-green. By comparison with the spectra observed in undoped and in Al-doped material before and after photoexcitation it is believed that the 1.8 eV band is due to the [PO4]− center and that the broad 2.45 eV band observed in Al- and Ga-doped BSO is due to the [BiO4]0 center.

A versatile Czochralski crystal growth system with automatic diameter control

A versatile Czochralski crystal pulling system with automatic diameter control for the growth of nonlinear optical oxide crystals is discussed. Pure and doped bulk single crystals of bismuth silicon oxide (Bi12SiO20) have been successfully grown using this system. The system consists of a regular Czochralski type pulling system with provision for continuous weighing of the growing crystal to provide feedback for power control.

Holographic-recording improvement in a bismuth silicon oxide crystal by the moving-grating technique

We investigate the enhancement of the diffraction efficiency of dynamic gratings recorded in a bismuth silicon oxide crystal at large modulation by the moving-grating technique. The optimum fringe velocity for maximum diffraction efficiency and the degree of enhancement of the diffraction efficiency at optimum fringe velocity are experimentally found to be dependent on the fringe modulation. We apply this technique to real-time incoherent correlation using bismuth silicon oxide. There are two main advantages in using moving gratings: First, the signal-to-noise ratio can be improved considerably because of the improved diffraction efficiency. Second, the resonant effect reduces the effect of environmental disturbances on the peak-correlation intensity, which is significant when the threshold detection level of the correlator is set.

Characterization of BSO crystals. A preliminary study

Czochralski grown bismuth silicon oxide (BSO) crystals have been investigated by mean of synchrotron X-ray topography in order to study the quality of the crystals obtained. High quality single crystals can be obtained under conditions rather deviated from the equilibrium. The first results correlating the defects observed with the type of the interface are reported

Polar habits of the Bi 12SiO 20 crystals grown by the Czochralski method

Crystals of bismuth silicon oxide (Bi 12SiO 20) with a diameter of 35 mm have been grown along 〈111〉 axes by the Czochralski method in an air atmosphere. The crystal morphology and the shapes of the crystal-melt interface are investigated. It has been shown that the shape of the growth interface changes from convex to concave towards the melt at a constant crystal diameter under the same pull and rotation rates throughout the growth. The inversion of the morphological polarity of the Bi 12SiO 20 crystal during parallel growth can be qualitatively accounted for on the basis of the approximate analysis of the thermal stress and strain caused by the nonuniform temperature distribution in the growing crystal, which was previously given by Brice.

Bi 12SiO 20 single crystal growth by the Bridgman method

The Bridgman growth of bismuth silicon oxide (BSO) crystals along 〈001〉, 〈110〉, 〈111〉 and 〈112〉 directions is reported in this paper for the first time. The mechanism of the darkened core formation in the Bridgman grown BSO crystals has been clarified on the basis of the investigation of the Czochralski growth of BSO. The possibility of the mass production of the core-free BSO crystals with high optical quality by the Bridgman method along 〈111〉 and 〈112〉 growth directions has been expounded.

Growth of bismuth silicon oxide and bismuth germanium oxide crystals by the Czochralski technique and their characterization

Photorefractive single crystals of bismuth silicon oxide (Bii2SiO2o) and bismuth germanium oxide (Bi12GeO2o) have been grown using the Czochralski technique. The experimental results are explained with the existing theoretical models. The grown crystals are characterized by x-ray, differential thermal analysis, scanning electron microscopy, IR transmission spectrum, and electron-probe microanalysis.

Some aspects of growth and characterisation of BSO and BGO crystals

Abstract Bismuth silicon oxide (BSO) and bismuth germanium oxide (BGO) crystals were grown by the Czochralski technique and the various parameters such as crystal rotation rate, pulling rate and growth temperature have been optimised for bubble free growth.

Growth of bubble-free bismuth silicon oxide and bismuth germanium oxide crystals under conditions of forced convection in the melt

Growth of bubble-free bismuth silicon oxide and bismuth germanium oxide crystals under conditions of forced convection in the melt

Low-defect colorless Bi12SiO20 grown by hydrothermal techniques

Colorless single crystals of bismuth silicon oxide (BSO) have been grown using a pressure-balanced hydrothermal technique. The absorption shoulder which causes the yellow coloration observed in conventional BSO was completely missing in the hydrothermal material. The 10 K absorption edge was found to be 3.45 eV for the hydrothermal samples. Because of the absence of a low-temperature photochromic response and the observation of only very weak TSC peaks, it appears that the hydrothermal crystals represent near-intrinsic BSO. When a crystal was pulled from a melt of hydrothermal material, the yellow coloration returned.

Photorefractive particle image velocimetry: performance enhancement with bismuth silicon oxide crystals

The polarization properties of diffraction from bismuth silicon oxide crystals are used to enhance the signal-to-noise ratio of a photorefractive particle image velocimeter. We explain these diffraction characteristics by using a simple picture of the processing steps and the beam-propagation method, accounting for the multiplicity of the recorded gratings. Experimental measurements are also presented.

Thermally stimulated current and photorefractivity of bismuth silicon oxide and bismuth germanium oxide

Nominally undoped crystals of bismuth silicon oxide and bismuth germanium oxide have been grown by the Czochralski method and characterized by thermally stimulated current (TSC) spectroscopy and optical grating erasing techniques. TSC spectra from crystal samples of the same boule were found to be highly reproducible and varied only moderately among platelets from different boules. In contrast, the protorefractive parameters determined from grating erasing experiments varied drastically even among samples from the same boule.

Competition between subharmonic and signal beams for photorefractive gain in BSO with two pump beams

It is shown that two pump beams incident upon a bismuth silicon oxide crystal give rise to a subharmonic beam bisecting the pump beam. Simultaneously a signal beam injected between the pump beams may be strongly amplified at the expense of the pump beams. It is shown that the amplified signal beam grows with a faster time constant than the subharmonic beam and that there is competition for gain in the steady state regime.