The refractive indices of AlxGa1−xAs epitaxial layers (0.176⩽x⩽1) are accurately determined below the band gap to wavelengths, λ<3 μm. The layers are grown on GaAs substrates by molecular beam epitaxy metal organic and chemical vapor deposition with thicknesses ranging from 4 to 10 μm. They form improper waveguide structures with the GaAs substrate. The measurements are based on the excitation of the improper waveguide modes with grating couplers at 23 °C. The refractive indices of the layers are derived from the modal propagation constants in the range of 730 nm<λ<830 nm with an estimated uncertainty of Δn=5×10−4. The temperature coefficient of the refractive index is investigated in the same spectral range. From the effective indices of the TE and TM modes, we derive the strain-induced birefringence and the elasto-optic coefficients. High-resolution x-ray diffraction is used to determine the strain of the layers. The layer compositions are obtained with inductively coupled plasma atomic emission spectroscopy. The measurement range of the refractive index is extended from the direct gap to λ<3 μm by observing the Fabry-Pérot interference fringes of the transmission spectra of isolated layers. The measured values of the refractive index and the elasto-optic coefficient are compared to calculated data based on semiempirical models described in the literature. Published data of the index of refraction on GaAs, AlAs and GaP are analyzed to permit the development of a modified Sellmeier approximation. The experimental data on AlxGa1−xAs can be fitted over the entire composition range 0⩽x⩽1 to provide an accurate analytical description as a function of composition, wavelength, and temperature.

A passive spatial light beam deflector based on a channel waveguide phased-array concept is presented. Diffraction gratings patterned by electron-beam lithography couple light into and out of the device. Phasing is achieved electro-optically with indium tin oxide/AlGaAs Shottky junctions. Discrete beam steering is first demonstrated with a 43-element rib waveguide array at an 850-nm wavelength. A sawtooth electrode keeps the device length short and the electrode surface small. Continuous deflection over a ±7.2 mrad range at a 900-nm wavelength is then reported. A set of seven sawtooth and offset electrodes permits addressing any point within this range. The beam has a width of 1.5 mrad, and the maximum modulation voltage is -8.5 V.

A GaAs surface grating (period 574 nm) is analyzed by four crystal-six reflection x-ray diffraction. Two-dimensional measurements in the vicinity of the 004 GaAs reciprocal lattice point show satellites in the transverse direction related to the periodicity of the grating. A cross pattern, centered on the 004 GaAs reciprocal lattice point, is formed by these satellites. An explanation is given by a model which includes the influence of transmission through the surface pattern on the substrate diffraction.

We report a new picosecond optical technique for observation of nonequilibrium carrier transport. An ’’overshoot’’ electron velocity of 4.4×107 cm/sec is observed at short times in GaAs under appropriate electric field conditions.

Careful investigation of the reflectivity of two very high finesse integrated Fabry–Perot interferometers is reported. These two structures, made of GaAs active layer (1.7 μm thick) surrounded by two superlattice/AlAs Bragg reflectors, exhibit vertical cw lasing action at and above room temperature when photopumped with thresholds of 16 mW at 300 K and 56 mW at 380 K. Reflectivity measurements together with theoretical calculations show that layer regularity, accurate thickness control, and low interface roughness are key parameters for high-performance structures. Transmission electron microscopy on cleaved wedges and reflection electron microscopy are shown to be unique tools for measuring and characterizing these layers. Electron microscopy, optical reflection, and laser linewidth measurements are correlated and show that the layer flatness is dramatically increased by the introduction of six (2.5 Å) GaAs wells in the AlAs growth of the integrated dielectric reflectors. Reflectives of 97%, Fabry–Perot finesse as high as 100 (61 for direct measurements), and laser linewidths as small as 1.2 Å are reported.

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Purposely disordered GaAs/Al Ga& As superlattices, followed by an enlarged well, were grown by molecular-beam epitaxy. Selective-excitation photoluminescence measurements were performed to study the energy dependence of the motion of resonantly photocreated excitons in disordered superlattices. We report the existence of different energy regions in the superlattice bands, corresponding to extended and spatially confined (localized) states induced by disorder. The temperature dependence of the photoluminescence spectra suggests the existence of activation energies for the localized states. This re'sects itself by an increase in the propagation rate of excitons by increasing the temperature. We compare qualitatively the experimental findings with a calculation of the superlattice miniband spectrum.