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  • 1990-1994  (31)
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  • 1
    Electronic Resource
    Electronic Resource
    Optical properties of two-dimensional photonic lattices fabricated as honeycomb nanostructures in compound semiconductors (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 687-689 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have experimentally studied two-dimensional photonic lattices, honeycomb nanostructures, fabricated by electron beam lithography with (Al,Ga)As materials. Surface normal optical properties were investigated by measuring reflectance to determine the effective index of refraction and lattice stability against degradation. Also, continuous wave and time-resolved luminescence spectroscopy was used to assess electron-hole recombination. Finally, light scattering was employed to study photon coupling and propagation through the lattice. These measurements show that the structures are stable, that nonradiative surface recombination is present, and that resonant coupling of light into/out of the lattice occurs at selected wavelengths satisfying a Bragg condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111034
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  • 2
    Electronic Resource
    Electronic Resource
    Built-in biaxial strain dependence of Γ-X transport in GaAs/InxAl1−xAs/GaAs pseudomorphic heterojunction barriers (x=0, 0.03, and 0.06) (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7907-7914 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of built-in biaxial strain on Γ-X transport in n-GaAs/i-InxAl1−xAs/n-GaAs pseudomorphic single-barrier structures (x=0, 0.03, and 0.06) are studied by measuring temperature-dependent I-V characteristics. For the accurate characterization of electron transport across each barrier, a self-consistent numerical model is used to analyze the experimental results. For each structure, the four barrier parameters defined from the thermionic-field-emission theory, the effective Richardson constant A*, the conduction-band offsets ΔEc1,2, and a tunneling mass mn* are extracted by calculating the theoretical I-V characteristics and fitting them to the experimental I-V-T data. The experimentally obtained X-point conduction-band shifts with the addition of indium are compared with the theoretical results calculated based on the model-solid theory. The results indicate that the addition of indium not only splits the degenerate X minima of the InxAl1−xAs barrier, but also shifts the relative barrier heights of both longitudinal and transverse X valleys due to the alloy-dependent band-structure modification. The comparison between the experimental and theoretical results illustrates that the transverse X valleys are the main conduction channel for the Γ-X transport across InxAl1−xAs pseudomorphic barriers. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357901
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  • 3
    Electronic Resource
    Electronic Resource
    Ultraviolet photosulfidation of III-V compound semiconductors: A new approach to surface passivation (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 2388-2390 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new passivation technique for III-V compound semiconductors based on ultraviolet photolysis of elemental sulfur vapor has been developed. Photosulfidation produces a greater increase in the photoluminescence intensity from GaAs samples than that produced by conventional (NH4)2S dip treatments and is more photostable than the conventional wet process. X-ray photoelectron spectroscopy of the photosulfided GaAs surfaces indicate formation of a surface sulfide rather than the disulfide characteristic of the (NH4)2S process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111623
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  • 4
    Electronic Resource
    Electronic Resource
    Low-voltage vertical-cavity transmission modulator for 1.06 μm (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 494-496 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present results on the first all-semiconductor, vertical Fabry–Perot-cavity optical transmission modulator. This device combined mechanically stable strained and unstrained (In,Al,Ga)As multilayers to achieve operation at 1.06 μm. Transmission-mode operation allows the resonant wavelength of the cavity to be finely tuned by varying the angle of incidence, providing, for the first time, a means of compensating for small inaccuracies in growth parameters. Using the modulator in double-pass operation with a corner-cube retroreflector, we demonstrate a tunable reflectance modulator with a fractional modulation of 25% at 3-V bias, suitable for applications in free-space communication.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109983
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  • 5
    Electronic Resource
    Electronic Resource
    Coherent beams from high efficiency two-dimensional surface-emitting semiconductor laser arrays (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 890-892 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated and operated large two-dimensional (2D) arrays of phase-locked surface-emitting semiconductor lasers. The arrays were fabricated by reactive ion beam etching of epitaxial Fabry–Perot resonators comprising GaAs/AlGaAs quantum wells surrounded by AlAs-AlGaAs quarter-wave mirrors. Different arrays corresponding to different pixel size (2–5 μm) and spacing (1–2 μm) were produced to investigate evanescent coupling between pixels. The arrays were photopumped so that the array size could be conveniently varied from 1×1, 2×2,... up to 20×20. Except for the 1×1 which emits a circular pattern, all arrays exhibit a well-defined four-lobed far-field pattern in agreement with our theoretical analysis of the optical modes which predicts domination by the 2D out-of-phase eigenmode. As a consequence this pattern can be understood with simple Fraunhofer diffraction theory. The angular spread of the lobes, determined by the periodicity of the array elements, is 10° for the array with element size/spacing of 4/1 μm. The widths of the lobes are 6.7° for the 2×2 and narrow to 3.2° with increasing number of pixels in the array. The array exhibits a sharp onset for lasing, operation on a single longitudinal mode, and a linewidth which narrows to ∼1 A(ring) with increasing array size. The differential power efficiency is as high as 70%. These observations provide further impetus and guidance for the development of 2D laser diode arrays.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104468
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  • 6
    Electronic Resource
    Electronic Resource
    Low threshold current implanted-planar buried-heterostructure graded-index separate confinement heterostructure laser in GaAs/AlGaAs (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1945-1947 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report dramatic improvements to the implanted-planar buried-heterostructure graded-index separate confinement heterostructure (IPBH-GRINSCH) laser in (AlGa)As/GaAs which produces low threshold current, continuous-wave operation. Our process features significantly reduced fabrication complexity of high quality, index-guided laser diodes compared to regrowth techniques and, in contrast to diffusion-induced disordering, allows creation of self-aligned, buried, blocking junctions by ion implantation. The improved single-stripe IPBH-GRINSCH lasers exhibit 39 mA threshold current, cw operation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103030
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  • 7
    Electronic Resource
    Electronic Resource
    Injection-locking characteristics of gain-guided diode laser arrays with an "on-chip'' master laser (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1521-1523 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report measurements of the injection-locking characteristics of a high-power continuous-wave diode laser array with an on-chip independently controlled master laser. This integrated injection-locked array emits a near-diffraction-limited single-lobed output beam at cw power levels up to 220 mW/facet. By controlling the current to the master laser, the single-lobed output beam can be electronically steered over a far-field angle of 〉1.7°. We also report preliminary studies of the coupling interaction in these integrated devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103162
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  • 8
    Electronic Resource
    Electronic Resource
    Optical properties of fractal quantum wells (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1736-1738 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the growth of new fractal quantum-well structures and the first studies of their optical properties. In these (Al,Ga)As structures the composition is varied in a fractal sequence between layers to create a highly branched, self-similar distribution of quantum wells. Experimentally, we studied optical absorption, luminescence and excitation spectra, and electron-hole recombination dynamics. We computed the electron and hole wave functions and transition energies and found good agreement with experiment. The optical and transport properties are strikingly different from those in single or periodic quantum wells. First, the band-edge absorption slope (change in optical density per unit energy) can be controlled over wide limits simply by modifying the sequence. Second, the transport of carriers across the quantum-well layers can be adjusted to control the carrier relaxation rate and energy distribution within the quantum wells. These results suggest possible applications of these new materials for several new devices including broadband emitters, solar cells, electro-optical, and nonlinear optical devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109590
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  • 9
    Electronic Resource
    Electronic Resource
    Optical Bloch waves in a semiconductor photonic lattice (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2714-2716 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed multiple optical Bloch waves in a semiconductor photonic lattice. This photonic lattice comprises epitaxial quarter-wave periodic layers surrounding a periodic quantum-well region. After growth, the layers are structured laterally into periodic square unit cells by reactive-ion-beam etching. When photoexcited, the lattice emits a complex angular distribution of photons that reflects its periodic structure. Scattered light is distributed according to the Laue conditions in analogy with x-ray diffraction from a bulk crystal. Optical Bloch waves photostimulated in the lattice are analogous to electron Bloch waves in an atomic lattice. These optical Bloch waves exhibit long-range translational symmetry and local symmetry due to the shape of the unit cell. Interestingly, the far-field pattern of stimulated emission gives a direct mapping of the allowed Bloch wave vectors in the Brillouin zone. The mapping exhibits a wave-vector gap at the Bragg condition and may be associated with a photonic energy gap. In addition to measuring the intensity distribution of these Bloch waves, we directly measure the phase of the wave by polarization shearing interferometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106853
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  • 10
    Electronic Resource
    Electronic Resource
    Epitaxial surface-emitting laser on a lattice-mismatched substrate (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2057-2059 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have demonstrated continuous-wave, room-temperature, photopumped operation of a vertical-cavity surface-emitting laser having a 0.8% lattice mismatch with its GaAs substrate. Such mismatch provides flexibility in designing resonators with new lasing wavelengths. The laser resonator comprises lattice-matched In0.12Ga0.88As and In0.10Al0.90As quarter-wave layers for mirrors and a strained-layer superlattice of In0.23Ga0.77As/Al0.35Ga0.65As for an active region. The structure lases in the range 1.05–1.10 μm under continuous-wave photoexcitation in the wavelength range 900–950 nm. The differential power efficiency is as high as 68% and the threshold is 2 kW/cm2 (1.8 kA/cm2 injection current-density equivalent). Dislocation line densities observed by photoluminescence microscopy are about 6×102/cm in both the active region and the uppermost mirror layers. The lines predominate along one 〈110〉 direction along which the laser light is preferentially polarized. These observations suggest a way of polarizing surface-emitting lasers by intentional patterning of grating lines on the wafer surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107088
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