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Dennis G. Hall - One of the best experts on this subject based on the ideXlab platform.

  • high order azimuthal spatial modes of Concentric Circle grating surface emitting semiconductor lasers
    Applied Physics Letters, 1998
    Co-Authors: Craig Olson, Dennis G. Hall, Pamela L Greene, G W Wicks, Steve Rishton
    Abstract:

    We report the emission properties of Concentric-Circle-grating, surface-emitting (CCGSE), distributed-feedback semiconductor lasers oscillating in single high-order azimuthal spatial modes. The evolution of the spatial profile of the beam emitted by such lasers with increasing excitation depends upon the spatial gain distribution and the depth of the circular waveguide grating. The polarization of the high-order spatial modes is predominantly radial.

  • highly directional surface emission from Concentric Circle gratings on planar optical waveguides the field expansion method
    Journal of The Optical Society of America A-optics Image Science and Vision, 1995
    Co-Authors: Rebecca H. Jordan, Dennis G. Hall
    Abstract:

    We describe the azimuthally polarized radiation field surface emitted by a shallow, Concentric-Circle grating located at the film–cover interface of a step-index, three-layer optical waveguide. We employ the field expansion boundary perturbation method to obtain an integral expression, correct to first order, for the radiation field produced when the surface perturbation scatters a transverse-electric, circularly symmetric, azimuthally polarized guided wave. We apply the method of stationary phase to the radiation integral to generate an algebraic expression for the far-field radiation. Plots of the radiation field are shown for waveguides with annular and full (extending from the origin) sets of Concentric-circular gratings that scatter incoming, outgoing, and standing circular guided waves.

  • radiation from Concentric Circle grating surface emitting planar waveguides the volume current method
    Applied Physics Letters, 1994
    Co-Authors: Rebecca H. Jordan, Dennis G. Hall
    Abstract:

    This letter describes the volume current boundary perturbation method and uses this method to find the field radiated by a set of Concentric rings located at the film‐cover interface of a three‐layer, planar optical waveguide. Waveguides with annular and full (extending from the origin) sets of circular gratings, and with both traveling and standing guided waves, are analyzed. The resulting analytical expression for the radiation field and far‐field intensity patterns are compared with results of the field‐expansion boundary perturbation method.

  • Curved grating fabrication techniques for Concentric-Circle grating, surface-emitting semiconductor lasers
    1993
    Co-Authors: Rebecca H. Jordan, Oliver King, Gary W. Wicks, Dennis G. Hall, Erik H. Anderson, M. J. Rooks
    Abstract:

    We describe the fabrication and operational characteristics of a novel, surface-emitting semiconductor laser that makes use of a Concentric-Circle grating to both define its resonant cavity and to provide surface emission. A properly fabricated circular grating causes the laser to operate in radially inward- and outward-going circular waves in the waveguide, thus, introducing the circular symmetry needed for the laser to emit a beam with a circular cross-section. The basic circular-grating-resonator concept can be implemented in any materials system; an AlGaAs/GaAs graded-index, separate confinement heterostructure (GRINSCH), single-quantum-well (SQW) semiconductor laser, grown by molecular beam epitaxy (MBE), was used for the experiments discussed here. Each Concentric-Circle grating was fabricated on the surface of the AlGaAs/GaAs semiconductor laser. The circular pattern was first defined by electron-beam (e-beam) lithography in a layer of polymethylmethacrylate (PMMA) and subsequently etched into the semiconductor surface using chemically-assisted (chlorine) ion-beam etching (CAIBE). We consider issues that affect the fabrication and quality of the gratings. These issues include grating design requirements, data representation of the grating pattern, and e-beam scan method. We provide examples of how these techniques can be implemented and their impact on the resulting laser performance. A comparison is made of the results obtained using two fundamentally different electron-beam writing systems. Circular gratings with period lambda = 0.25 microns and overall diameters ranging from 80 microns to 500 microns were fabricated. We also report our successful demonstration of an optically pumped, Concentric-Circle grating, semiconductor laser that emits a beam with a far-field divergence angle that is less than one degree. The emission spectrum is quite narrow (less than 0.1 nm) and is centered at wavelength lambda = 0.8175 microns.

  • circularly symmetric operation of a Concentric Circle grating surface emitting algaas gaas quantum well semiconductor laser
    Applied Physics Letters, 1992
    Co-Authors: Turan Erdogan, Oliver King, Dennis G. Hall, Erik H. Anderson, G W Wicks, M. J. Rooks
    Abstract:

    A surface‐emitting semiconductor laser that utilizes a Concentric‐Circle grating defined by electron‐beam lithography is observed to oscillate in a circularly symmetric fashion. The laser emits a circularly symmetric beam with a total beam divergence of less than 1°. Despite its broad‐area geometry, the laser shows no evidence of filamentation. The laser maintains a relatively narrow wavelength spectrum approximately 1 A in width.

M. J. Rooks - One of the best experts on this subject based on the ideXlab platform.

  • Curved grating fabrication techniques for Concentric-Circle grating, surface-emitting semiconductor lasers
    1993
    Co-Authors: Rebecca H. Jordan, Oliver King, Gary W. Wicks, Dennis G. Hall, Erik H. Anderson, M. J. Rooks
    Abstract:

    We describe the fabrication and operational characteristics of a novel, surface-emitting semiconductor laser that makes use of a Concentric-Circle grating to both define its resonant cavity and to provide surface emission. A properly fabricated circular grating causes the laser to operate in radially inward- and outward-going circular waves in the waveguide, thus, introducing the circular symmetry needed for the laser to emit a beam with a circular cross-section. The basic circular-grating-resonator concept can be implemented in any materials system; an AlGaAs/GaAs graded-index, separate confinement heterostructure (GRINSCH), single-quantum-well (SQW) semiconductor laser, grown by molecular beam epitaxy (MBE), was used for the experiments discussed here. Each Concentric-Circle grating was fabricated on the surface of the AlGaAs/GaAs semiconductor laser. The circular pattern was first defined by electron-beam (e-beam) lithography in a layer of polymethylmethacrylate (PMMA) and subsequently etched into the semiconductor surface using chemically-assisted (chlorine) ion-beam etching (CAIBE). We consider issues that affect the fabrication and quality of the gratings. These issues include grating design requirements, data representation of the grating pattern, and e-beam scan method. We provide examples of how these techniques can be implemented and their impact on the resulting laser performance. A comparison is made of the results obtained using two fundamentally different electron-beam writing systems. Circular gratings with period lambda = 0.25 microns and overall diameters ranging from 80 microns to 500 microns were fabricated. We also report our successful demonstration of an optically pumped, Concentric-Circle grating, semiconductor laser that emits a beam with a far-field divergence angle that is less than one degree. The emission spectrum is quite narrow (less than 0.1 nm) and is centered at wavelength lambda = 0.8175 microns.

  • circularly symmetric operation of a Concentric Circle grating surface emitting algaas gaas quantum well semiconductor laser
    Applied Physics Letters, 1992
    Co-Authors: Turan Erdogan, Oliver King, Dennis G. Hall, Erik H. Anderson, G W Wicks, M. J. Rooks
    Abstract:

    A surface‐emitting semiconductor laser that utilizes a Concentric‐Circle grating defined by electron‐beam lithography is observed to oscillate in a circularly symmetric fashion. The laser emits a circularly symmetric beam with a total beam divergence of less than 1°. Despite its broad‐area geometry, the laser shows no evidence of filamentation. The laser maintains a relatively narrow wavelength spectrum approximately 1 A in width.

  • spatial modes of a Concentric Circle grating surface emitting algaas gaas quantum well semiconductor laser
    Applied Physics Letters, 1992
    Co-Authors: Turan Erdogan, Oliver King, Dennis G. Hall, G W Wicks, C L Dennis, M. J. Rooks
    Abstract:

    We demonstrate the fabrication and operation of an AlGaAs surface‐emitting semiconductor laser, grown by molecular‐beam epitaxy, that incorporates a circularly symmetric grating of period Λ=0.25 μm fabricated using electron‐beam lithography. Azimuthal variations in the grating linewidth have a significant impact on the spatial modes of the laser.

G W Wicks - One of the best experts on this subject based on the ideXlab platform.

D.g. Hall - One of the best experts on this subject based on the ideXlab platform.

  • azimuthal mode discrimination in radially chirped Concentric Circle grating distributed feedback lasers
    IEEE Journal of Quantum Electronics, 2000
    Co-Authors: C. Olson, D.g. Hall
    Abstract:

    We report a theoretical investigation analyzing the threshold modes of a Concentric-Circle-grating (CCG) distributed feedback laser with a radially chirped first-order Bragg grating. A numerical coupled-mode analysis of a chirped CCG laser shows improved azimuthal mode discrimination for chirped gratings with linear, quadratic, and square-root radial dependence. Negatively chirped gratings, in which the grating period decreases with radius, result in improved threshold discrimination between the circularly symmetric fundamental mode and higher order modes; positively chirped gratings, in which the grating period increases with radius, result in decreased threshold for higher order modes in general. Also, the intensity for the fundamental mode at the grating center can be reduced by an order of magnitude using linearly chirped gratings.

  • Radiation patterns of higher azimuthal order spatial modes from a Concentric-Circle-grating waveguide cavity using the volume-current method
    IEEE Journal of Quantum Electronics, 1998
    Co-Authors: C. Olson, D.g. Hall
    Abstract:

    We calculate the surface-emitted scattered radiation from a Concentric-Circle-grating waveguide cavity. The full vector form of the scattered radiation is calculated using the volume-current method, where the index perturbation caused by the grating is represented as an induced-current driving term in the free-space wave equation for the scattered field. We show intensity patterns and field vector plots for a range of azimuthal modes besides the previously reported fundamental mode, and we find excellent agreement with the observed emission patterns and field polarization from Concentric-Circle-grating surface-emitting semiconductor lasers.

Turan Erdogan - One of the best experts on this subject based on the ideXlab platform.