R.S. Burton

Carnegie Mellon University, Pittsburgh, PA, United States

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Publications (15)21.55 Total impact

  • R.S. Burton, T.E. Schlesinger
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    ABSTRACT: We discuss the effects of waveguide geometry on the radiation loss of tightly curved multimode dielectric waveguides. Three waveguide geometries are investigated: a ridge waveguide, a buried waveguide, and an interdiffused waveguide. We compare the effective index method with both semi- and full-vectorial method-of-lines analyses for these waveguide geometries. This comparison shows that the effective index method is accurate for curved waveguides except where the outer confinement region is in cut-off or, in the case of TM-polarization, for the ridge waveguide. In the latter case, the full-vectorial method-of-lines predicts a resonant feature of the TM-mode radiation loss of curved ridge waveguides; this is not predicted by either the semivectorial method-of-lines or the effective index method
    Journal of Lightwave Technology 03/1996; · 2.56 Impact Factor
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    ABSTRACT: Numerical simulation based on the scalar beam propagation method, was used to investigate the performance of waveguide electrooptic beam deflectors. The deflectors under investigation consist of a stack of electrooptically controlled prisms in a waveguide. The results were compared to earlier simplified analysis. It was found that for given overall device dimensions, the number of interfaces between prisms in a prism-type electrooptic deflector has significant influence on the device performance when it is small. To avoid wavefront distortion, unwanted reflection from the interfaces, and asymmetry in the deflection angles caused by small number of interfaces, one should use more than about ten interfaces in a typical deflector. Additional insights of device operation and design issues are discussed
    Journal of Lightwave Technology 11/1995; · 2.56 Impact Factor
  • R.S. Burton, T.E. Schlesinger
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    ABSTRACT: The radiation loss of curved ridge dielectric waveguides can show an oscillatory dependence on radius for the TM-polarisation. This effect is predicted only by a three-dimensional full vectorial analysis and is confirmed experimentally in S-bend dielectric ridge waveguides
    Electronics Letters 08/1995; · 1.04 Impact Factor
  • R.S. Burton, T.E. Schlesinger
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    ABSTRACT: The authors present an improvement to the method-of-lines technique which significantly decreases the computations required to achieve accurate solutions for the propagating modes of three-dimensional dielectric waveguides. This method is applied to a circular dielectric waveguide to assess its advantages
    Electronics Letters 07/1994; · 1.04 Impact Factor
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    ABSTRACT: The authors present a novel design for a Y-junction splitter for ring waveguides based on the principle of mode conversion by self-interference. Power in the device is diverted from an edge-guided ring mode into a straight guide with little loss to radiation modes. The power injected into the fundamental modes of both the straight and ring guides is maximised relative to higher order modes
    Electronics Letters 07/1994; · 1.04 Impact Factor
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    ABSTRACT: We have investigated, by simulation, the coupling efficiencies of a ring laser into a straight guide in terms of the power splitting ratio between the fundamental modes of the ring and straight output guide, as well as the proportion of power lost to higher-order excitations of the straight guide. The results show that the typical design for a branching ring laser can be optimized by offsetting the output guide position and choosing the proper guide width. This analysis also shows that the symmetrical dual output port design (i.e. tangential straight guide) can result in very poor output coupling efficiencies as compared to the single output port design
    Journal of Lightwave Technology 06/1994; · 2.56 Impact Factor
  • R.S. Burton, T.E. Schlesinger
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    ABSTRACT: Results are presented on the wet thermal oxidation of AlxGa1-xAs. The growth of wet thermal oxides of AlxGa1-xAs is shown to be linear with time. An O2 carrier gas was found to form a self‐terminating oxide for compositions investigated (x≳0.4), but required elevated temperatures for substantial growth. The use of a medium oxygen concentration (∼20%) in a N2 carrier formed nonuniform oxides for all compositions investigated. A low O2 concentration (0.1%) in the N2 carrier was found to reduce the activation energy of the oxidation process for Al0.6Ga0.4As from 1.9 to 1.0 eV while increasing the activation energy of Al0.8Ga0.2As from 1.6 to 1.75 eV. For these wet thermal oxides it is observed that lateral oxidation at heterojunction interfaces is enhanced. This enhanced lateral oxidation can be attributed to local stress due to the smaller volume of the growing oxide compared to the volume of the consumed semiconductor.
    Journal of Applied Physics 01/1994; 76(9):5503-5507. · 2.21 Impact Factor
  • R.S. Burton, T.E. Schlesinger
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    ABSTRACT: A semiempirical relation has been developed for determining the minimum allowable radius of curvature of a circular waveguide with an edge-guided fundamental mode. The specified parameters are the wavelength, the effective refractive index of the waveguide, the lateral index step, and the allowable radiation loss coefficient. This relation was fitted and verified against numerically evaluated solutions of Maxwell's equations in two dimensions for lateral index steps 0.01<ΔN<0.1, for effective indices of refraction 3<N<4 (appropriate for the GaAs/Al<sub>x</sub>Ga<sub>1-x</sub>As system), and for radiation losses of 10<sup>-4</sup> <α<sub>r</sub><100 cm<sup>-1</sup>. The difference between the results of solving Maxwell's equations and the semiempirical relation over these parameter ranges was determined to be less than 2%
    Journal of Lightwave Technology 01/1994; · 2.56 Impact Factor
  • Richard S. Burton, Tuviah E. Schlesinger
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    ABSTRACT: We have investigated, via the beam propagation method, waveguide designs for wide window single-mode single-stripe lasers. The expanded window allows for higher power operation of the laser diode owing to the lower power density at the facets. Higher-order transverse mode suppression is achieved by incorporating a spatial filter in the waveguide that preferentially allows propagation of the fundamental mode. These devices can be fabricated using existing laser diode fabrication technologies such as reactive-ion-etching, native oxidation, or impurity- induced-disordering, and buried heterostructure processes. In our design and analysis of these devices we compare several expanding waveguides to determine the effects on mode selection. Additionally, the catastrophic optical damage power limit for these devices is expected to be significantly greater than for simple fundamental-mode single-stripe lasers.
    Proc SPIE 01/1994;
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    ABSTRACT: Process conditions for fabricating Si‐O impurity‐induced layer disorder defined Al x Ga 1-x As‐GaAs buried heterostructure quantum well lasers utilizing a fully self‐aligned planar process and conventional As free open‐tube‐furnace annealing are presented. An SiO 2 layer, deposited by sputtering, was used as a diffusion source for Si and O impurities as well as a source for Ga vacancies that enhance impurity diffusion and allow for a reduction in the required annealing temperature and time. A self‐aligned native oxide of the Al x Ga 1-x As cladding layer was used to form a Zn diffusion mask and dielectric layer. Lasers fabricated using this process exhibited threshold currents as low as 2.72 mA and external differential quantum efficiencies of 79% at room temperature in continuous operation.
    Journal of Applied Physics 03/1993; · 2.21 Impact Factor
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    ABSTRACT: In this paper, we present numerical simulations, based on the beam propagation method (BPM), of a Gaussian beam deflected by a thin-film electro-optic (EO) deflector. The results are compared to geometric optics calculations and experimental data. From the BPM simulation, it is clear that one should choose a larger number of interfaces for prism-like EO deflectors in order to obtain a predictable deflection angle and good beam quality
    Lasers and Electro-Optics Society Annual Meeting, 1993. LEOS '93 Conference Proceedings. IEEE; 01/1993
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    ABSTRACT: The effective index method has been used to calculate eigenmodes of AlGaAs optical waveguides to determine optimal process parameters for their fabrication and to compare the advantages and disadvantages of several different fabrication technologies for the integration of waveguides and lasers.
    Proc SPIE 07/1992;
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    ABSTRACT: Process conditions for fabricating ridge geometry Al x Ga 1-x As‐GaAs quantum well heterostructure laser arrays utilizing a high quality self‐aligned native oxide of Al x Ga 1-x As are presented. Wet oxidation is performed, after etching ridges, via H 2 O vapor in a N 2 or N 2 /H 2 (10%) carrier gas at 435–445 °C for 15–20 min. The formation of a uniform smooth oxide was found to be critically dependent on the crystal environment prior to the oxidation process. Characteristics of devices fabricated by this process are presented.
    Applied Physics Letters 05/1992; · 3.79 Impact Factor
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    ABSTRACT: The wavelengths of separate-confinement quantum-well heterostructure semiconductor lasers have been tuned by applying mechanical stress through a piezoelectric transducer. In addition, photoluminescence measurements have been made on GaAs samples stressed with piezoelectric bimorphs. It is shown that measurable shifts in the energy gap can be obtained by mechanically stressing the semiconductor with a microelectromechanical system (MEMS) transducer. The authors demonstrate MEMS-induced wavelength tuning with four independent phenomena: photoluminescence, photoresponse, lasing, and electroluminescence
    Micro Electro Mechanical Systems, 1992, MEMS '92, Proceedings. An Investigation of Micro Structures, Sensors, Actuators, Machines and Robot. IEEE; 03/1992
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    ABSTRACT: A unified process for integrating lasers, detectors, modulators, and waveguides for optoelectronic integrated circuits (OEICs) on a single substrate is described. The devices are fabricated from a quantum well heterostructure (QWH). Initial efforts have been directed toward fabricating these devices in a ridge waveguide form because of the simplicity of fabrication. A QWH is grown by metalorganic chemical vapor deposition (MOCVD) and modified as necessary to produce detectors, modulators, and waveguides. The detector is essentially given, because the laser structure can be operated with no bias (no dark current) and photogenerated carriers will be swept out of the quantum well by the large built-in field. The waveguides are produced by etching a ridge to induce an effective lateral index step, as are the other devices, and the GaAs quantum well can also be slightly disordered using Ga vacancy diffusion to shift the absorption edge of the waveguide to a longer wavelength than the emission wavelength of the laser. The modulator regions may be Ga vacancy diffused or not, depending on the modulator type and function. The characteristics of an inline laser-modulator-detector structure are reviewed. Results of modeling ridge waveguide structures for Δβ modulators are discussed. Several self-aligned fabrication processes that have the best prospects for reliable integration of lasers, detectors, modulators, and waveguides are introduced
    High Speed Semiconductor Devices and Circuits, 1991., Proceedings IEEE/Cornell Conference on Advanced Concepts in; 09/1991