IEE Proceedings - Optoelectronics
Volume 144, Issue 6, December 1997
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Volume 144, Issue 6
December 1997
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- Author(s): T. Fessant
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 6, p. 365 –376
- DOI: 10.1049/ip-opt:19971345
- Type: Article
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p.
365
–376
(12)
DFB lasers with longitudinal variations in their grating pitch and, consequently, their Bragg wavenumber (corrugation-pitch-modulated or CPM-DFB) can achieve single-mode oscillation with good threshold gain margins and flatter longitudinal photon-density distributions than conventional quarter-wave-shift (QWS) DFB lasers. Moreover, substantial improvements of these two characteristics are provided by adequate variation of the coupling coefficient κ along the cavity In the paper, a three-section corrugation-pitch-modulated DFB laser with distributed-coupling-coefficient (DCC-CPM-DFB) is studied extensively. Threshold and above-threshold numerical simulations show that these structures can achieve very good single-mode operation by correct optimisation of the Bragg detuning and coupling strength profile at threshold and can maintain these characteristics up to high injection currents. - Author(s): S.-T. Shih ; M.-H. Chen ; W.-W. Lin
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 6, p. 377 –382
- DOI: 10.1049/ip-opt:19971344
- Type: Article
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p.
377
–382
(6)
The authors investigate the distortion of demodulated output signals in a fibre-optic Michelson interferometric sensor with respect to the imperfect properties of its 3 × 3 coupler. A general guideline is also suggested for choosing a 3 × 3 coupler and its connection type in the interferometer to reduce this kind of signal distortion. - Author(s): J.A. Besley ; J.D. Love ; G.B. Scelsi
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 6, p. 383 –388
- DOI: 10.1049/ip-opt:19971609
- Type: Article
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p.
383
–388
(6)
The authors investigate the performance of an evanescent-field fibre sensor made from standard single-mode optical fibre with a tapered cladding region, upon which a thin attenuating material coating is deposited. The authors' method involves calculating the supermodes of the complete core-cladding-coating-air structure locally at each point along the taper and studying the evolution of the supermode guided power along the sensor. Results are compared with those from a numerical finite difference scheme; and also used to interpret experimental results obtained for a taper with a thin layer of sulphur deposited by electrical discharge in an atmosphere of SF6. - Author(s): W.R. Smith ; J.R. King ; B. Tuck
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 6, p. 389 –396
- DOI: 10.1049/ip-opt:19971389
- Type: Article
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p.
389
–396
(8)
A time-dependent mathematical model describing coupled electrical, optical and thermal effects in semiconductor lasers is introduced. A numerical scheme devised to solve the model is presented. The results of a simulation are exhibited for a particular laser design. - Author(s): J. Zubia and J. Arrue
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 6, p. 397 –403
- DOI: 10.1049/ip-opt:19971561
- Type: Article
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p.
397
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(7)
The authors have analysed how bending, torsion and tensile stresses affect the dispersion and polarisation in a plastic optical fibre. This respectively becomes locally uniaxial and inhomogeneous, biaxial and inhomogeneous, and uniaxial and homogeneous, with little variation in the dispersion. The polarisation changes rapidly and the induced anisotropy is of the order of that produced in the manufacturing process. - Author(s): S.J. Chang ; C.S. Chang ; Y.K. Su ; P.T. Chang ; Y.R. Wu ; K.H. Huang ; T.P. Chen
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 6, p. 405 –409
- DOI: 10.1049/ip-opt:19971554
- Type: Article
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p.
405
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(5)
AlGaInP DH, DH + DBR and MQW LEDs were fabricated and their luminescence properties were compared. It was found that AlGaInP MQW LEDs are brighter than DH and DH + DBR LEDs, particularly under low current injection. For MQW LEDs, the EL intensity will increase as the number of wells increases. Furthermore, the output intensity is also a function of the barrier layer thickness lB. As lB increases, the EL intensity will become larger. Reliability tests under DC and pulse operation were measured and it was found that the AlGaInP MQW LEDs used in this study are more reliable than the DH + DBR LED. Under pulse operation it was found that, as the number of wells increases, the amount of decay will become smaller. - Author(s): J.A. Besley and J.D. Love
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 6, p. 411 –419
- DOI: 10.1049/ip-opt:19971381
- Type: Article
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p.
411
–419
(9)
An analysis is presented of propagation along practical, single-mode matched-cladding and depressed-cladding slab waveguides and fibres using the bound modes of the entire core-cladding–coating–air cross-section, instead of the usual bound-radiation-mode model of a finite core and unbounded cladding. The model readily quantifies the spatial transient in terms of modal absorption and scattering in the coating, and also displays leaky-mode behaviour, as well as the characteristic transmission dips associated with the fundamental mode beyond its cutoff wavelength in a depressed-cladding fibre. - Author(s): R.P. Sarzała and W. Nakwaski
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 6, p. 421 –425
- DOI: 10.1049/ip-opt:19971300
- Type: Article
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p.
421
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(5)
The radial carrier diffusion process inside active regions of gain-guided vertical-cavity surface-emitting lasers (VCSELs) is studied rigorously. To this end, a comprehensive three-dimensional self-consistent VCSEL simulation is used. In the modelling, carrier degeneracy as well as temperature and carrier-concentration dependencies of the diffusion coefficient are taken into account. For the room-temperature operation of the GaAs/AlGaAs/AlAs proton-implanted top-surface-emitting VCSELs, ambipolar diffusion coefficient was found to be relatively low (≃ 7.5 cm2/sec) and nearly constant inside the active region but it increases rapidly beyond this region. It is, however, proved that although very accurate VCSEL modelling requires rigorous treatment of the carrier diffusion process, an average constant value of the diffusion coefficient may be undoubtedly used in quite reliable VCSEL simulations. - Author(s): G. Dale and P.J.S. Ewen
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 6, p. 426 –432
- DOI: 10.1049/ip-opt:19971347
- Type: Article
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p.
426
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(7)
Gratings are fabricated by the metal-photodissolution effect in evaporated As33S67 glass, using a novel method which may overcome the disadvantages of previous methods based on holographic or contact mask exposure. The proposed method involves the generation of the initial metal pattern (Ag or Cu) on a substrate, followed by evaporation of the chalcogenide overlayer. Ag gratings with periods, Λ, of 12, 10, 8 and 6 µm and depths, d, of 0.35–0.42 µm have been fabricated in this way. This approach offers more flexibility than previous methods, and has interesting potential for the fabrication of curved-profiled microstructures (e.g. microlens arrays) by the appropriate exposure or heating regime. The stability of the gratings is investigated by monitoring the time-resolved diffraction efficiency during photodissolution of the metal grating source into the As33S67 overlayer. - Author(s): K. Inoue
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 6, p. 433 –437
- DOI: 10.1049/ip-opt:19971455
- Type: Article
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p.
433
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(5)
Waveform distortion due to gain saturation in a semiconductor optical amplifier (SOA) is studied numerically for different signal formats, NRZ and Manchester code. It is shown that the eye-opening penalty is nearly 0 dB for Manchester format sampled in the second half of one bit period while it increases with SOA input power or with signal bit rate for NRZ. It is also shown that extinction degradation for Manchester code is smaller than that for NRZ. These results are due to the fact that the signal level frequently changes between ON and OFF states and the pattern effect is small in Manchester format. - Author(s): A.G. Deryagin ; N.N. Faleev ; V.M. Smirnov ; G.S. Sokolovskii ; V.I. Vasil'ev
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 6, p. 438 –440
- DOI: 10.1049/ip-opt:19971456
- Type: Article
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p.
438
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(3)
The paper is concerned with the study of the growth of AlGaSb, AlGaAsSb and InGaAsSb epilayers, which are lattice-matched to GaSb, by means of liquid-phase epitaxy (LPE) from Sb-rich melts. The obtained composition ranges were 0.02 ≤ x ≤ 0.20 for AlxGa1–xSb, AlxGa1–xAsySb1–y epilayers and 0.04 ≤ x ≤ 0.24 for InxGa1–xAsySb1–y layers. In the PL spectra measured on AlGaSb and GaInAsSb direct-gap solid solutions, only peaks with a maximum corresponding to the bandgap were observed. No long-wavelength peaks, which correspond to defects such as VGa+GaSb and are typical of GaSb and related solid solutions grown from In- or Ga-rich melts, were found in PL spectra of the epilayers obtained.
Threshold and above-threshold analysis of corrugation-pitch-modulated DFB lasers with inhomogeneous coupling coefficient
Analysis of fibre optic Michelson interferometric sensor distortion caused by the imperfect properties of its 3 × 3 coupler
Local supermode analysis of tapered fibre sensor
Mathematical modelling of thermal effects in semiconductor laser operation
Theoretical analysis of the modal dispersion induced by stresses in a multimode plastic optical fibre
AlGaInP multiquantum well light-emitting diodes
Supermode analysis of fibre transmission
Carrier diffusion inside active regions of gain-guided vertical-cavity surface-emitting lasers
Photolithographic method for producing metal-dissolved diffractive structures in As-S glasses
Waveform distortion in a gain-saturated semiconductor optical amplifier for NRZ and Manchester formats
High quality AlGaSb, AlGaAsSb and InGaAsSb epitaxial layers grown by liquid-phase epitaxy from Sb-rich melts
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