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1887

IEE Proceedings J (Optoelectronics)

Volume 138, Issue 5, October 1991

Volumes & issues:

Volume 138, Issue 5

October 1991

Editorial: Quantum wells in optoelectronics
QUANTUM WELLS IN OPTOELECTRONICS: Laser-induced transient photoconductivity in MQW systems
  • Author(s): B.K. Ridley  and  P.J. Bishop
  • Source: IEE Proceedings J (Optoelectronics), Volume 138, Issue 5, p. 294 –298
  • DOI:  10.1049/ip-j.1991.0051
  • Type: Article
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  • p. 294 –298 (5)
    In the interpretation of laser-induced transient photoconductivity a number of effects have to be taken into account. The most important of these are considered to be those associated with excitons, degeneracy, photon recycling, mobility variations and the nonuniformity of carrier injection. These effects are discussed and modifications are made, by including the boson character of the exciton and its four-fold spin degeneracy, to the theory of radiative recombination. A simple estimate of the effect of photon recycling in thin MQWs is given. The density dependence of mobility in an electron-hole plasma is argued to be small, except when higher subbands become populated or the quantum wells become full. In the latter case saturation of the photoconductivity, which can occur at low laser intensities with nonuniform injection, is expected. The importance of both the exponential decay in the degenerate regime and the observed intensity dependence of the initial amplitude is emphasised.
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QUANTUM WELLS IN OPTOELECTRONICS: Optimisation threshold parameters of multiple quantum well infra-red photodetector
QUANTUM WELLS IN OPTOELECTRONICS: Absorptive bistability in inhomogeneously pumped quantum well laser diodes
  • Author(s): I. Middlemast ; J. Sarma ; K.A. Shore ; A.I. Kucharska ; E.D. Fletcher ; P. Blood
  • Source: IEE Proceedings J (Optoelectronics), Volume 138, Issue 5, p. 301 –308
  • DOI:  10.1049/ip-j.1991.0053
  • Type: Article
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  • p. 301 –308 (8)
    The purpose of this paper is to provide a study of optical bistability in inhomogeneously pumped multiquantum well (MQW) laser diodes. To achieve this aim, gain and spontaneous emission data, calculated for a specific MQW laser material structure, have been incorporated into a model of an inhomogeneously pumped laser diode. Results are presented which show a number of differences between the bistable behaviour of MQW and bulk GaAs segmented devices. Experimental results are included to provide a basis for a qualitative comparison with the theoretical model.
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QUANTUM WELLS IN OPTOELECTRONICS: Polarisation dependence of refractive index of MQW waveguides
  • Author(s): S.I Hansen ; J.H. Marsh ; J.S. Roberts
  • Source: IEE Proceedings J (Optoelectronics), Volume 138, Issue 5, p. 309 –312
  • DOI:  10.1049/ip-j.1991.0054
  • Type: Article
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  • p. 309 –312 (4)
    The polarisation dependence of the refractive index of a multiple quantum well wave-guide has been investigated using the grating coupler technique. The use of a layer of anti-reflection coating during the holographic definition of the gratings allows high contrast ratios to be routinely achieved, and by defining the grating coupler in a low-index material on top of the semiconductor and simplifying the measurement procedure, the precision of the results is enhanced and the timefactor of the measurements is reduced. Over the range of wavelengths from 840 to 880 nm, the refractive index of the multiple quantum well material was observed to change by 8 × 10−2 and 6.7 × 10−2 for the transverse electric and transverse magnetic polarisations, respectively. The birefringence of the material was observed to increase from 1.4 × 10−2 at 880 nm to 2.7 × 10−2 at 840 nm.
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QUANTUM WELLS IN OPTOELECTRONICS: GaAs/GaAlAs graded index separate confinement single quantum well single-mode waveguide electroabsorption light modulator
  • Author(s): L.D Zhu ; F.K. Xiong ; C.M. Wang ; Z.H. Chen ; Y.L. Hsie ; G.A.B. Feak ; J.M. Ballantyne
  • Source: IEE Proceedings J (Optoelectronics), Volume 138, Issue 5, p. 313 –318
  • DOI:  10.1049/ip-j.1991.0055
  • Type: Article
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  • p. 313 –318 (6)
    A GaAs/GaAlAs graded-index separate confinement single quantum well heterostructure single-mode ridge waveguide electroabsorption modulator was fabricated and investigated. For the modulator with a quantum well width of 100 Å and device length of 700 μm, an on/off ratio of 29.7 dB and estimated absorption insertion loss of 3 dB were obtained for TE polarised light with wavelength 8650 Å, and for TM polarisation the on/off ratio was 28.5 dB. With a switching voltage of 1 V, an on/off ratio of 15 dB was achieved. Photocurrent spectra exhibited a red shift of 600 Å of the absorption edge when the voltage applied to the PIN diode was varied from 0.5 to −7 V. The corresponding shift of the room temperature exciton peak energy was 96 meV.
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QUANTUM WELLS IN OPTOELECTRONICS: Design and fabrication of packaged InP/InGaAsP multiple quantum well waveguide components with very low insertion loss
  • Author(s): T.G. Lynch ; M.D.A. MacBean ; R.H. Walling ; A.R. Thurlow
  • Source: IEE Proceedings J (Optoelectronics), Volume 138, Issue 5, p. 319 –322
  • DOI:  10.1049/ip-j.1991.0056
  • Type: Article
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  • p. 319 –322 (4)
    The design of a multiple quantum well (MQW) waveguide with low fibre-to-fibre loss, suitable for optoelectronic device integration, is described. The devices were grown by atmospheric pressure MOVPE and designed to be matched to standard, lensed optical fibre. Measured propagation loss was (0.75 ± 0.1) dB cm−1 with a fibre-to-fibre loss of (2.6 ± 0.1) dB. Analysis shows that the coupling loss due to mode mismatch was less than (0.52 ± 0.14) dB/facet, believed to be the lowest reported coupling loss to a semiconductor waveguide using lensed fibre. A device packaged using laser welding to fix the fibres had a total insertion loss of (3.9 ± 0.1) dB giving less than 1.3 dB excess loss due to the packaging process.
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QUANTUM WELLS IN OPTOELECTRONICS: Linear and nonlinear optical properties of direct gap Si-Ge superlattices
  • Author(s): R.J. Turton  and  M. Jaros
  • Source: IEE Proceedings J (Optoelectronics), Volume 138, Issue 5, p. 323 –329
  • DOI:  10.1049/ip-j.1991.0057
  • Type: Article
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  • p. 323 –329 (7)
    Optical properties of Si-Ge superlattices grown on virtual substrates are investigated with a view to engineering optimum characteristics. The oscillator strength and transition energy, both across the fundamental gap and between the conduction sub-bands, are examined as a function of the choice of substrate and well/barrier width. In the former case, the transition energy is shown to be tunable in the range 0.6–1.0 eV which covers the technologically important optical fibre ‘window’ at 1.55 μm. Intersub-band transitions occur at wavelengths in the far infrared. A strong nonlinear optical response can also be achieved via a novel virtual excitation mechanism. Growth parameters are presented for systems in which this response is maximised while keeping the absorption to a minimum.
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Finite-cladding fibres: HE12 and local-normal-mode coupling evolution
  • Author(s): R.J. Black ; J. Bures ; J. Lapierre
  • Source: IEE Proceedings J (Optoelectronics), Volume 138, Issue 5, p. 330 –336
  • DOI:  10.1049/ip-j.1991.0058
  • Type: Article
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  • p. 330 –336 (7)
    A discussion of the evolution of the HE12 (LP02) field, and thus the rôle of the core in HE11-H12 (LP01-LP02) local-mode coupling for a tapered ‘doubly-clad’ lightguide as may be formed by the combination finite-cladding fibre and external medium (i.e. outer cladding) is presented. Consideration of more than one interface injects interesting novel features into the local-normal-mode viewpoint: examination of the HE12 lobe maximum and field evolution leads to the discovery of a core/cladding bounce phenomenon (related to an HE12 leaky-mode property) as well as an intriguing coupling phase dependence.
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Multichannel grating cavity (MGC) laser transmitter for wavelength division multiplexing applications
  • Author(s): K.O. Nyairo ; I.H. White ; P.A. Kirkby ; C.J. Armistead
  • Source: IEE Proceedings J (Optoelectronics), Volume 138, Issue 5, p. 337 –342
  • DOI:  10.1049/ip-j.1991.0059
  • Type: Article
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  • p. 337 –342 (6)
    A detailed experimental investigation of a wavelength switchable multichannel grating cavity (MGC) laser is reported with properties particularly suitable for applications in broadband wavelength division multiplexing systems. The source consists of a bar of laser ridges with one facet antireflection (AR) coated, a collimating lens and a diffraction grating. By changing the electrical bias to individual laser ridges, precise wavelength switching is achieved across the complete gain spectrum of the diode laser material. A detailed investigation of multiple simultaneous channel generation is reported and a method is outlined to overcome channel crosstalk. Good agreement between theory and experiment is reported.
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Tapered single-mode fibres and devices. Part 1: Adiabaticity criteria
  • Author(s): J.D. Love ; W.M. Henry ; W.J. Stewart ; R.J. Black ; S. Lacroix ; F. Gonthier
  • Source: IEE Proceedings J (Optoelectronics), Volume 138, Issue 5, p. 343 –354
  • DOI:  10.1049/ip-j.1991.0060
  • Type: Article
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  • p. 343 –354 (12)
    Two complementary delineation criteria are presented which provide guidelines to the design of relatively short, low-loss tapered fibres and devices. They are used to explain anomalous loss effects in depressed-cladding and W-fibres, as well as the difficulty in fabricating low-loss devices by tapering such fibres. Practical application of the criteria to couplers, beam expanders and abrupt taper filters is summarised. The accompanying paper provides both experimental and theoretical justification for the delineation criteria.
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Tapered single-mode fibres and devices. Part 2: Experimental and theoretical quantification

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