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Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 19, Issue 17, 18 August 1983

Volumes & issues:

Volume 19, Issue 17

18 August 1983

Negative differential resistance in GaAs MESFETs
Fitting of a weighted Gaussian lowpass filter to the transfer function of graded-index fibres to reduce bandwidth ambiguities
Linewidth of a single mode in a multimode injection laser
Laser-beam attenuation measurement using acousto-optic modulator
Joint-loss dependence on mismatch parameters in graded-index optical fibres
Wavelength tuning of GaInAsP/InP integrated laser with butt-jointed built-in distributed Bragg reflector
Solid-state devices in H-guide, groove guide and fence guide
New method for equivalent-step-index fibre determination
Optical losses in metal/SiO2-clad Ti:LiNbO3 waveguides
  • Author(s): L.L. Buhl
  • Source: Electronics Letters, Volume 19, Issue 17, p. 659 –660
  • DOI:  10.1049/el:19830449
  • Type: Article
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  • p. 659 –660 (2)
    We present measured excess loss resulting from electrode overlays for both TE and TM polarisations as a function of SiO2 buffer layer thickness for Ti:LiNbO3 strip waveguides at λ = 1.32 μm. We find there is negligible excess loss to the TE mode with no buffer layer and that the excess loss to the TM mode can be essentially eliminated with a SiO2 layer only 700 Å thick. A passive polariser with ̃ 1.5 dB fibre-waveguide-fibre insertion loss and > 13 dB extinction ratio is also demonstrated.
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Far-field distribution of semiconductor phase-locked arrays with multiple contacts
  • Author(s): J. Katz ; E. Kapon ; C. Lindsey ; S. Margalit ; A. Yariv
  • Source: Electronics Letters, Volume 19, Issue 17, p. 660 –662
  • DOI:  10.1049/el:19830450
  • Type: Article
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  • p. 660 –662 (3)
    Experimental results of far-field patterns of semiconductor laser arrays with multiple contacts are reported. It is found that, by tailoring the distribution of the currents through the array elements, narrow single-lobe patterns—which are more useful in most applications—can be obtained from arrays that usually operate in a double-lobe mode. A diffraction-limited 1.8°-wide far-field pattern was obtained from a three-element array.
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Incident wavelength dependence of pulse responses in InP/InGaAsP/InGaAs avalanche photodiodes
Emission frequency stability in single-mode-fibre optical feedback controlled semiconductor lasers
  • Author(s): F. Favre  and  D. le Guen
  • Source: Electronics Letters, Volume 19, Issue 17, p. 663 –665
  • DOI:  10.1049/el:19830452
  • Type: Article
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  • p. 663 –665 (3)
    A newly designed semiconductor laser emitter with adjustable linewidth by controlling the coupling to a single-mode fibre is described with emphasis on thermal requirements to obtain a high-frequency stability. A stable operation has been achieved during more than 1 h using an AlGaAs laser diode with optical feedback from a 50 cm-long single-mode fibre resulting in a 50-fold reduction of the spectral linewidth.
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Ka-band Y-circulators in integrated waveguide technology
Electroplated Au-GaAs1−xPx and Au-Ga1−xAlxAs Schottky barriers
  • Author(s): M. López-Coronado ; M. Aguilar ; M.T. Martínez ; E. Calleja ; E. Muñoz
  • Source: Electronics Letters, Volume 19, Issue 17, p. 666 –668
  • DOI:  10.1049/el:19830454
  • Type: Article
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  • p. 666 –668 (3)
    A novel technique based on pulse electroplating and surface treatment with very slow etching rate solutions has been applied to fabricate Au Schottky barriers on GaAs1−xPx and Ga1−xAlxAs. Device characteristics are compared to the behaviour of vacuum-deposited barriers. The present technique allows a simple and fast procedure to obtain Schottky barriers for material evaluation and device applications.
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Generation of single-longitudinal-mode gigabit-rate optical pulses from semiconductor lasers through harmonic-frequency sinusoidal modulation
Low-temperature expitaxial growth of (100) silicon
  • Author(s): M. Milosavljević ; C. Jeyens ; I.H. Wilson
  • Source: Electronics Letters, Volume 19, Issue 17, p. 669 –671
  • DOI:  10.1049/el:19830456
  • Type: Article
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  • p. 669 –671 (3)
    Epitaxial silicon films have been grown onto as-received and implanted (100) silicon wafers by electron-beam evaporation. A high-temperature treatment to remove native oxide was not employed. Optimum temperatures for epitaxial growth were between 600°C and 700°C. Deposition rates were from 30 to 80 nm/min and the operating pressure was < 5 × 10 − 7 mbar. The Rutherford backscattering spectra of the optimum films have values of χmin indistinguishable from that of a bulk wafer (3.9%).
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Fibre-optic digital transmission experiment with heterodyne detection
Wavelength-discriminating photodetector for lightwave systems
  • Author(s): J.C. Campbell ; C.A. Burrus ; J.A. Copeland ; A.G. Dentai
  • Source: Electronics Letters, Volume 19, Issue 17, p. 672 –674
  • DOI:  10.1049/el:19830458
  • Type: Article
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  • p. 672 –674 (3)
    We demonstrate that a dual-wavelength photodetector can be used to determine simultaneously the wavelength and the power level of a lightwave signal. The signal wavelength is determined by monitoring the ratio of the two outputs from this photodetector at the crossover of its responsivity curves; the signal level is determined from the sum of the two outputs. Possible applications for this type of photodetector include mode-control of single-frequency injection lasers, direct demodulation for lightwave systems utilising frequency-shift-keyed transmission, wavelength-division multiplexing and optical logic.
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Optical fibre jacketed with high-modulus low-linear-expansion-coefficient polymer
Double-square frequency-selective surfaces and their equivalent circuit
Easily trimmed third-order RC-active-filter section with finite transmission zeros
Bend behaviour of polarising optical fibres
Improved feed network for group-type unidirectional transducers
  • Author(s): G. Macchiarella  and  G. Viola
  • Source: Electronics Letters, Volume 19, Issue 17, p. 680 –681
  • DOI:  10.1049/el:19830463
  • Type: Article
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  • p. 680 –681 (2)
    In the letter we propose a phasing and matching network for group-type unidirectional transducers (GT-UDTs) which takes into account the electroacoustic interactions between the two phases of the GT-UDT. In comparison with analogous feed circuits from the literature, this network represents an improvement as far as the reduction of the residual fluctuations in the passband frequency response of a GT-UDT device is concerned.
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Modification of phase-locked-loop performance using a sample-and-hold circuit
Universal multiple-output second-order digital filter
  • Author(s): C. Eswaran  and  A. Antoniou
  • Source: Electronics Letters, Volume 19, Issue 17, p. 683 –684
  • DOI:  10.1049/el:19830465
  • Type: Article
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  • p. 683 –684 (2)
    A universal, second-order, digital-filter structure is proposed, which realises simultaneously a lowpass, a highpass, a bandpass, a notch and allpass transfer function. The structure uses two unit-delays and four multipliers, and is quite attractive for VLSI implementation since a versatile universal chip can be fabricated, which can be used for the implementation of Butterworth, Cheby̅shev and elliptic digital filters as well as digital equalisers.
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Subthreshold currents in CMOS transistors made on oxygen-implanted silicon
  • Author(s): D.J. Foster
  • Source: Electronics Letters, Volume 19, Issue 17, p. 684 –685
  • DOI:  10.1049/el:19830466
  • Type: Article
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  • p. 684 –685 (2)
    Kinks have been observed in subthreshold current plots of mesa-shaped n-channel transistors made on oxygen implanted silicon substrates. The kinks represent additional current flow and are due to overlapping fields from the gate electrode causing early corner inversion and to a Qss side-wall effect. Subthreshold currents in n-channel transistors are dominated by the two effects which, as a consequence, reduce threshold voltages especially in narrow n-channel transistors. The subthreshold characteristics of p-channel transistors were not affected in the same way.
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Totally self-checking checker for 3N arithmetic codes
Practical single-polarisation anisotropic fibres
Comment: Quantum mechanical explanation of spontaneous emission K-factor
Polarisation-mode dispersion as bandwidth-limiting factor in a long-haul single-mode optical-transmission system
  • Author(s): K. Suzuki ; N. Shibata ; Y. Ishida
  • Source: Electronics Letters, Volume 19, Issue 17, p. 689 –691
  • DOI:  10.1049/el:19830470
  • Type: Article
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  • p. 689 –691 (3)
    Polarisation-mode dispersion and fibre length dependence of extinction ratio between two orthogonally polarised HE11 modes are measured for predicting bandwidth limitation in high-capacity transmission systems. For a single-mode fibre with 10% core ellipticity and 0.5% refractive-index difference, 3 dB bandwidth and available bit rate after 50 km transmission are evaluated to be 4.8 GHz and 8.8 Gbit/s at v = 2.2, respectively.
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Frequency-selective combline directional couplers designed as novel filters and multiplexers
Comparing the chromatic dispersions of two single-mode silica fibres with pure F and pure GeO2 doping, respectively
New and simple method for selective mode group excitation in graded-index optical fibres
  • Author(s): A.K. Agarwal ; G. Evers ; U. Unrau
  • Source: Electronics Letters, Volume 19, Issue 17, p. 694 –695
  • DOI:  10.1049/el:19830473
  • Type: Article
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  • p. 694 –695 (2)
    A modified monomode-fibre offset technique as well as a new and very simple method for selective mode excitation in multimode graded-index fibres is presented. It is shown that an inclined plane wave launch followed by a mandrel-wrap mode filter is a powerful way to excite a definite number of mode groups in graded-index fibres. Besides its extreme simplicity this method yields improved selectivity. Experimental results are presented.
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CMOS current comparator circuit
Simulation of GaAs submicron FET with hot-electron injection structure
Polarimetric strain gauges using high birefringence fibre
1.3 μm InGaAsP/InP multiquantum-well lasers grown by vapour-phase epitaxy
New method for determining the series resistances in a MESFET or TEGFET
Simple coding scheme for modular arithmetic
Equivalent-circuit consideration of dual-gate MESFETs at high frequency
Erratum: Relevance of complex normalisation in precision reflectometry

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