Ce3+ : Y3Al5O12 (Ce : YAG) is an important phosphor in high intensity CRT displays since it does not saturate at high electron beam power. The saturation power level is of the order of 1 W/cm2 for most cathodoluminescent materials, and this limits the maximum surface brightness of a typical cathode ray tube. However, Ce3+ : YAG has been found to be linear to at least 104 W/cm2. This performance has encouraged our examination of another cerium activated phosphor, lanthanum beryllate, Ce : La2Be2O5 (Ce : BEL). A crystal of lanthanum beryllate activated with a cerium concentration of 41018 atoms/cm3 was grown by the Czochralski crystal growth technique. Wafers were prepared from the crystal and analyzed in both the as-grown state and after annealing in a flowing atmosphere of 10% by volume hydrogen in argon at 1150 °C for 4 h. Cathodoluminescent measurements revealed a broadband blue emission of 100 nm width centered at 480 nm, a blue-shifted analog of the Ce : YAG spectrum. A linear efficiency of 0.13 lm/W was found to a power loading of 8 W/cm2. Pulsed excitation of a Ce : BEL crystal by 375 nm radiation produced by frequency doubling of a 750 nm laser demonstrated a decay time of the fluorescence of the order of 50 ns. All these data show that Ce : La2Be2O5 is an excellent candidate as a blue phosphor for high intensity CRT applications, particularly for high resolution projection displays using single crystal faceplates.

Thin films of bismuth-substituted lutetium iron garnet (BiLuIG) for the magnetostatic wave (MSW)-optical-mode interaction can be grown by liquid-phase epitaxy from the standard PbO-based melt system developed for yttrium iron garnet (YIG). The addition of MgO to the melt to counteract the effect of lea on the ferromagnetic resonance (FMR) linewidth is investigated. BiLuIG thin films were grown on paramagnetic gadolinium gallium garnet substrates with varying amounts of MgO added. The ferromagnetic resonance linewidth, optical waveguide absorption, and MSW passband were measured. The addition of magnesium reduced the FMR linewidth from an average of 3 Oe down to under 1 Oe, with little effect on other parameters.

A common electro-optic interface (EO) has been designed and tested with a new optic sensor decoding architecture. The new EO module converts Wavelength Division Multiplexed (WDM) position, temperature and pressure signals using the same circuitry. This module uses the combination of Digital Signal Processing (DSP) technology along with a new temperature and pressure sensing technology. This approach results in common circuitry for processing three dissimilar inputs. The new architecture was made possible by advancements in two major areas, DSP and growth of advanced materials with tailored optic properties. This paper will discuss both the top level architecture of sensors and EO module and the performance advantages.

Waveguides of high refractive index aluminum garnets have been epitaxially grown on 〈111〉-oriented crystal wafers of yttrium aluminum garnet (Y3Al5O12, YAG) and clad with epitaxial YAG. Epitaxy was by the liquid phase solution growth technique from supercooled mixtures of lead oxide and boron oxide, as is common for the epitaxy of iron garnets. One composition which is particularly suited for waveguides is Tb1.78Lu1.22Al5O12, which has a refractive index at 632.8 nm of about 1.854, as compared with 1.828 for YAG, and has no absorption bands in the visible and near IR spectra. Since aluminum garnets have melting points above 1900 °C, such waveguides should find application in high temperature optical sensors.

Planar waveguides of high refractive index aluminum garnets containing magnetic rare-earth cations have been epitaxially grown on <111≳-oriented crystal wafers of yttrium aluminum garnet (Y3Al5O12, YAG). Epitaxy was by the liquid phase solution growth technique from supercooled mixtures of lead oxide and boron oxide, as is common for the epitaxy of the magneto-optical iron garnets. The liquid phase epitaxy technique is well established for aluminum garnets, so that mixed garnet compositions, such as (Ra,Rb)3Al5O12, can be prepared easily as crystal layers on YAG. The typical lattice constant mismatch which is tolerated for defect-free epitaxy is about 0.1%. Reduction of stress-induced birefringence demands a still closer matching of the epitaxial layer to the substrate, of the order of 0.01%. Such matching to a YAG substrate can be achieved in mixed garnet compositions, such as (Ra,Rb)3Al5O12, in which Ra and Rb are large and small cations which average to the cationic size of yttrium. One composition which is particularly suited for magneto-optical waveguides is Tb1.65Lu1.35Al5O12, which has a refractive index at 632.8 nm of about 1.8545, as compared with 1.8280 for YAG, and has no absorption bands in the visible and near-IR spectra. The room temperature Verdet constant of this composition has been measured over the wavelength range of 500–675 nm, and it is comparable to that of Tb3Al5O12. Magnetic field modulation of light intensity of 4.4 ppm/cm/Oe at 632.8 nm has been measured in a planar waveguide of the Tb1.65Lu1.35Al5O12 composition. Since aluminum garnets have melting points greater than 1900 °C, such waveguides should find application in high temperature magneto-optical sensors and isolators.

Germanium is found to be a growth inhibitor in the liquid phase epitaxy of yttrium aluminum garnet. Germanium oxide additions to PbO/B2O3 fluxed melts for the liquid phase epitaxy of Y3Al5O12 and Ce:Y3Al5O12 on Y3Al5O12 substrates reduce the epitaxial growth rate in an effect similar to that with calcium oxide additions to melts for the growth of Y3Fe5O12. In contrast, cerium oxide additions to Y3Al5O12 melts have no measurable effect on growth rate. Germanium oxide additions reduce the growth rate sensitivity with supercooling, at saturation temperatures near 900 °C, as an essentially linear decreasing function of the germanium oxide concentration, GeO2/(GeO2+2Al2O3), where GeO2 and Al2O3 are the molar concentrations of germanium and aluminum oxide in the melt.

Epitaxial phosphor faceplates of cerium-activated yttrium aluminum garnet (YAG) phosphor (P-46) have been prepared on single-crystal YAG faceplates up to 3-in in diameter. Photolithographic reticulation of the faceplates was performed to increase the external efficiency of the epitaxial phosphor. A 1*1 in raster on a 2-in-diameter faceplate has produced a faceplate luminance of 62700 fL with a 40-kV excitation at an efficiency of 4.84 lm/W. This is 435 lm from a 1-in/sup 2/ raster at 90-W/in/sup 2/ excitation. Extrapolated performance of 2000 lm is expected from 3-in diameter (2.75-in-diagonal raster) faceplates.<>

A magneto-optical garnet composition has been developed for use in a multimode, two-port, fiberoptic wheel rotation rate sensor for aerospace applications. The sensor utilizes a layer of (Bi, Y, Gd, Tm, Lu, Ca)3(Fe, Si)5O12 grown on a (111)-oriented substrate of Gd3Ga5O12 by standard liquid-phase-epitaxy techniques. The sensor has an integral biasing magnet and lensless coupling of multimode glass fibers to a polarizer/garnet/analyzer sandwich. The sensor operates at a signal channel of 725 nm and a reference channel of 850 nm, convenient wavelengths for semiconductor emitters and detectors. The (Bi, Y, Gd, Tm, Lu, Ca)3 (Fe, Si)5O12 layer is grown to 25-μm thickness on one side of the substrate. It has a saturation field of 500 Oe, Curie temperature of 530 K, and the following approximate room-temperature optical properties at 725 nm: a Faraday rotation of 15°, an optical attenuation of 5 dB, a specific rotation of 0.65°/μm, a specific attenuation of 0.25 dB/μm, and a figure of merit of 2.5°/dB. The low figure of merit is a consequence of the strong optical absorption of iron cations in the near infrared, but it is sufficient for this device. Gadolinium and thulium incorporation onto dodecahedral lattice sites serves the dual purpose of reducing the saturation magnetization and reducing the temperature dependence of magnetization. Device operation is specified over a temperature range of −65 to 450°F (−54 to 232°C), but layers of slightly higher Curie temperature allow operation to an upper temperature limit of 550°F (288°C).

Bismuth-doped lutetium iron garnet (BLIG) is an important material for implementation of the interaction between magnetostatic waves and optical guided modes. Sodium oxide is suggested to reduce the viscosity of the lead-free melt used for liquid-phase epitaxy (LPE) growth of the films, improving flux removal. The effect of the incorporation of sodium into the garnet lattice on the important magnetic and magneto-optic properties is studied, using yttrium iron garnet as a model system. Negligible effect on the Faraday rotation and magnetostatic wave passband is noted. The uniaxial anisotropy field is affected in the negative direction by a growth induced anisotropy due to sodium inclusion, 'but this effect may be removed by annealing.

Calcium oxide is a growth rate inhibitor of the liquid-phase epitaxy (LPE) of garnet layers. Calcium oxide additions to a melt for the growth of yttrium iron garnet (YIG) will reduce the epitaxial growth rate from its typical value of 1.0 to 0.1 μm/min [W. H. De Roode and J. M. Robertson, J. Cryst. Growth 63, 105 (1983)], allowing precise thickness control for the fabrication of optical waveguides and magnetic heterostructures. LPE growth of YIG from calcium-free melts produces a 0.1-0.5 μm interface layer between the YIG layer and the gadolinium gallium garnet (GGG) substrate. This interface is caused by a transient crystal growth that occurs before equilibrium epitaxy, and it consists of a nonstoichiometric layer composition that includes flux and impurity components. Calcium oxide addition would be especially useful if it reduced the thickness of the interface layer in proportion to its inhibition of growth rate. This, however, is not the case. A series of Ca:YIG layers was grown by LPE on GGG substrates in the thickness range 0.05–10 μm. Faraday rotation spectroscopy in the wavelength range 475–575 nm distinguished the layer, interface, and substrate contributions to the optical rotation and revealed the presence of a 0.25-μm-thick interface layer with properties characteristic of Pb-substituted YIG. Double-crystal x-ray diffraction confirmed the existence of the interface by the angular broadening of the layer diffraction and a shifting to lattice constants intermediate between YIG and GGG as the layer thickness decreased. The importance of this interface as a graded refractive index layer in optical waveguides should not be overlooked.

Sodium chloride (NaCl), and sodium chloride with sodium oxide (Na2O), were used as solvents for the solution growth of β-barium borate, the low temperature form of BaB2O4. Crystal growth rate is extremely rapid in BaB2O4-NaCl solutions, but growth rate is reduced with addition of Na2O. The crystals exhibit smooth facet faces which are not apparent in growth from Na2O without NaCl. The crystal habit changes from blade, or needle, shaped for BaB2O4-NaCl solutions, to prismatic, or semi-spherical, as Na2O is added. Reduction in crystal clarity by flux inclusion became more severe as the Na2O concentration of the growth solution was increased. This is believed to result from retained carbonate in solution from the Na2CO3 used as a precursor for Na2O.

B-BaB204 has recently been demonstrated as a promising material for both SHG and OPO applications, particularly in the UV region. We have successfully grown 0-BaB204 in a novel flux composition consisting of NaCl and Na20. Crystal growth rate was very fast in a pure NaC1 flux with well developed facets. Na20 was added as a retardant to slow down both the growth rate and spurious nucleation. The crystal habit also changed from long-prismatic shape to more equant semispherical. As the Na20 concentration increased, the crystal clarity was also reduced because of more severe flux inclusion. We believed that this was due to the contamination of carbonate in the flux since Na2CO3 was used as a pre-cursor for Na20.

Epitaxial layers of 81% 57Fe-enriched Y3Fe5O12 were grown on thick, (100)-oriented substrates of Gd3Ga5O12 for experiments in resonant nuclear diffraction. Layers up to 10 μm thick were grown on each side of 32-mm-diam, 5-mm-thick wafers using techniques common for the growth of magnetic bubble materials, but with the use of a PbO-V2O5 flux in place of the usual PbO-B2O3 flux. The PbO-V2O5 flux offers a lower solubility of YIG which allows a reduction in the amount of 57Fe oxide required for layer growth. Thick substrates were used to reduce possible bowing from lattice constant mismatch. Lead incorporation onto yttrium lattice sites was controlled by adjusting the growth temperature, and this allowed a close lattice constant match between the layers and the substrate. Layer thickness was essentially uniform across the layer diameter with the edges 5% thicker than the center. Curie temperature and Faraday rotation measurements of the equivalent (111)-oriented material indicate as a formula unit (Y2.96Pb0.04)Fe3(Fe1.94Y0.06)O12. YIG/YIG double-crystal diffraction by tungsten L-γ1 irradiation of a 5×7-mm rectangular area of the first crystal gave a composite linewidth of 13 arcsec for the {400} reflection. This same linewidth was observed in synchrotron illumination of the central 80% of the area of the first layer. The possibility of linewidth reduction in this material is discussed.

Compressive epitactic layers grown on single-crystal substrates are shown to substantially improve mechanical durability. In this study, neodymium-substituted gadolinium gallium garnet (GGG) layers are grown on undoped GGG substrates. The layers are found to dramatically improve the abrasion resistance of the substrates, but to have only a slight effect on strength. Abrasion treatments, which cause up to 20 times decrease in the strength of substrates without epitactic layers, do not cause a significant decrease in the strength of substrates with these compressive surface layers. This permits the high strength of specially prepared strong substrates to be retained after abrasion.