W. A. Bonner

Acousto‐optic light deflectors using optical activity in paratellurite

Light deflector designs which use the anomalously low shear wave acoustic velocity and high acousto‐optic figure of merit in single‐crystal paratellurite, first proposed by Uchida and Ohmachi, have been made practical by exploiting this materials birefringence to circularly polarized light. Dixons equations for Bragg interaction in birefringent materials are found to be equally applicable to optically active materials when linearly polarized propagation modes are replaced by circularly polarized modes. For specific ratios of sound‐to‐light wavelengths, there is a substantially expanded angular range over which Bragg interaction can take place. One effect of this increased range is to permit longer interaction lengths between light and sound, which greatly reduces the acoustic power required. In paratellurite, for visible light, this expanded range occurs for sound frequencies below 100 MHz, in the region of acceptable acoustic loss. Examples of possible designs include a deflector only 3×5×7 mm having a...

A NEW AND STABLE NONLINEAR OPTICAL MATERIAL

The nonlinear coefficient d31 of K.6Li.4NbO3 is equal to d31 of LiNbO3. Also, the serious problem of optically induced refractive‐index inhomogeneities which has been observed in many nonlinear materials, notably LiNbO3, is not observed in this new material. The electro‐optic half‐wave voltage of this new material is 930 V.

Some characteristics of niobates having “filled” tetragonal tungsten bronze-like structures

Abstract Alkali metal and mixed alkali metal-alkaline earth niobates having “filled” tetragonal tungsten bronze-like structures are of particular interest for electro-optic and nonlinear optic applications. The characteristics of a number of the more useful materials and particularly Ba 2 NaNb 5 O 15 , Sr 2 NaNb 5 O 15 , and K 3 Li 2 Nb 5 O 15 are considered in some detail here.

LEAD MOLYBDATE: A MELT‐GROWN CRYSTAL WITH A HIGH FIGURE OF MERIT FOR ACOUSTO‐OPTIC DEVICE APPLICATIONS

Crystalline lead molybdate PbMoO4 has been found to be well suited for acousto‐optical device applications. This material has desirable properties similar to the previously reported α‐iodic acid α‐HIO3. However, PbMoO4, unlike α‐HIO3, is insoluble in water and can therefore be readily fabricated into devices and its optical surfaces do not require protection from the atmosphere. The elastic, photoelastic, optical, and thermal properties of PbMoO4 have been measured. These data have been used in the design of several acousto‐optic devices. An example consisting of a two stage (horizontal and vertical) acoustically driven light deflector is described. Each stage of this deflector has an 80‐MHz bandwidth and can deflect over 50% of an incident laser beam (5145 A) with less than 1 W of electrical drive power.

Deep radiative levels in InP

Results of a detailed photoluminescence study of deep radiative transitions in InP crystals prepared by the bulk and epitaxial techniques are reported. In order to understand the origin of the photoluminescence (PL) spectra, bulk samples were subjected to isothermal anneals at different partial pressures of phosphorus. Similarly, the liquid phase epitaxy (LPE) wafers were grown with and without phosphorus in the gas stream. The electrical nature of some of the species responsible for the PL emission was inferred by a study of Cd diffused bulk samples. Based on these experiments the following tentative assignments are proposed. The photoluminescence band at 0.99 eV, common to all samples, is due to emission from a donorlike level related to the P vacancy. Bands at 1.21 and 1.14 eV appear to be due to emission to native acceptor levels associated with the In vacancy. The 1.08‐eV band is attributed to emission to a complex of the donor (0.99 eV) and acceptor (1.21 eV) species. The relationship between these ...

Spinodal decomposition in InGaAsP epitaxial layers

Abstract In GaAsP epitaxial layers emitting in the 1.25−1.37 μm wavelength region have been evaluated using transmission electron microscopy, X-ray diffraction and photoluminescence. Electron diffraction patterns show elongation of the 400 spots in the direction and diffuse intensity on the low angle as well as on the high angle side. This observation is consistent with the extra scattering observed close to the 400 Bragg peaks by X-ray diffraction. Furthermore, microstructures exhibit quasi periodic fine scale structure having a wavelength of ≈ 150 A, rectilinear boundaries and a weakly developed basket-weave pattern. These observations are compatible with the occurrence of spinodal decomposition in the layers. In addition, photoluminescence studies indicate that the presence of the fine scale composition modulations does not adversely affect the luminescence properties of these materials.

InP synthesis and LEC growth of twin-free crystals

Abstract Techniques for the synthesis of InP at the equilibrium vapor pressure of the melt via gradient freeze, and the reproducible growth of twin-free crystals by LEC are discussed. In addition, an in-situ post-growth annealing procedure for twin-free LEC crystals, which minimizes the effects of growth induced stress and that resulting from differential thermal contraction between the InP crystal and the B 2 O 3 skin adhering to it after growth, is reported.

The growth of K0.6Li0.4NbO3 crystals for electro-optic and non-linear applications

Single crystals of ferroelectric K0.6Li0.4NbO3 can be grown from the melt by slow cooling or by the Czochralski technique. A preferred form is obtained when an excess of alkali metal is present. This material has good optical properties, is desirable for electro-optic and non-linear applications and is stable to 0.488 μm radiation at least to the 0.3 W level.

Magnetic properties of a number of divalent transition metal tungstates, molybdates and titanates

Magnetization data taken between room temperature and 1.4°K are reported for MIIMVIO4 compounds (wherein MII = Mn, Co, Ni and Cu and MVI = W and Mo) for Li2M(MoO4)3 (where M = Co, Ni, and Cu) and for CoTiO3. The dependence of Neel temperature upon the electronegativity of the cation present is discussed.

Molecular beam epitaxial growth of uniform In0.53Ga0.47As on InP with a coaxial In‐Ga oven

Epitaxial layers of In0.53Ga0.47As lattice matched to InP substrates have been grown by molecular beam epitaxy. The (100) InP substrate surfaces were first oxide passivated and then thermally cleaned under 1.5×10−6 Torr of arsenic moleuclar beam exposure (i.e., 1.24×1014 As4/cm2 sec). When they were heated to 500 °C, damage‐free surfaces without oxygen and carbon contamination were obtained. The surface chemical composition as a function of the thermal cleaning temperature was studied with Auger electron spectroscopy. In0.53Ga0.47As epilayers of highly uniform composition were grown over a 7‐cm2 InP substrate using an In/Ga coaxial oven design. Reproducible In and Ga beam fluxes to obtain lattice‐match condition were achieved by adjusting the aperture ratio of the In and Ga reservoirs, and the oven temperature. Net electron concentration as low as 3×1015 cm−3 has been achieved for the In0.53Ga0.47As layers.