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Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 24, Issue 18, 1 September 1988

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Volume 24, Issue 18

1 September 1988

High-power, high-efficiency 770 nm 2D laser diode array
Polarisation-independent LiNbO3, 4×4 matrix switch
Low threshold current GaAs/AlGaAs GRIN-SCH lasers grown by molecular beam epitaxy on Si3N4 masked substrates
  • Author(s): H.P. Meier ; E. van Gieson ; W. Walter ; C. Harder ; P. Buchmann ; D. Webb ; A. Moser
  • Source: Electronics Letters, Volume 24, Issue 18, p. 1123 –1125
  • DOI:  10.1049/el:19880764
  • Type: Article
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  • p. 1123 –1125 (3)
    High-performance single-quantum-well graded-refractive-index separate confinement heterostructure (SQW GRIN-SCH) lasers have been grown by molecular beam epitaxy on Si3N4 patterned GaAs (100) substrates. Lasers grown on stripe windows orientated in the [011] direction have optical waveguiding and current confinement supplied by facetting occurring during growth. Lasers fabricated on 10μm wide Si3N4 openings have threshold currents as low as 15 mA for a 500 μm-long cavity. The current density required to reach optical transparency is 144 A/cm2, an internal quantum efficiency of 81%, and a peak optical power of 70 mW per facet has been obtained. Device performance comparable to ridge lasers is observed in a self-aligned laser process.
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Explanation and modelling of pulse compression and broadening in near-travelling-wave laser amplifiers
Evaluation of power penalty due to beat noise induced by connector reflection
  • Author(s): M. Shikada  and  N. Henmi
  • Source: Electronics Letters, Volume 24, Issue 18, p. 1126 –1128
  • DOI:  10.1049/el:19880766
  • Type: Article
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  • p. 1126 –1128 (3)
    Power penalties caused by beat noise in a received optical signal beam were evaluated experimentally and theoretically. It was found that power penalties could be suppressed when the beam relative intensity noise was reduced to less than −135 dB/Hz below 2.4 Gbit/s. This goal can be satisfied using a commercially available physical contact optical connector, which has less than −20 dB reflection.
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CMOS delay time model based on weighted peak current
Dynamic performance of current-sensing power MOSFETs
Measurement of intrinsic frequency response of semiconductor lasers using optical modulation
  • Author(s): C.H. Lange ; J. Eom ; C.B. Su ; J. Schlafer ; R.B. Lauer
  • Source: Electronics Letters, Volume 24, Issue 18, p. 1131 –1132
  • DOI:  10.1049/el:19880769
  • Type: Article
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  • p. 1131 –1132 (2)
    For the first time, optical modulation is used to determine the intrinsic frequency response of a laser diode. It is shown that the shape of the measured frequency response agrees very well with the predicted intrinsic response of semiconductor lasers. As anticipated, the measured frequency response lacks the frequency rolloff that occurs with direct RF current modulation. The resonant frequencies measured are shown to be proportional to the square root of the probe laser bias power and the damping rates are found to be linear in power, in agreement with expectations.
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Wide bandwidth low noise pinFET receiver for high-bit-rate optical preamplifier applications
  • Author(s): L.D. Tzeng  and  R.E. Frahm
  • Source: Electronics Letters, Volume 24, Issue 18, p. 1132 –1134
  • DOI:  10.1049/el:19880770
  • Type: Article
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  • p. 1132 –1134 (3)
    A wide bandwidth low noise pinFET receiver has been fabricated and characterised for optical preamplifier applications. The receiver uses a low capacitance planar pin diode as the photodetector. A bandwidth of 7.08 GHz was measured. The measured input noise current for the receiver front-end is lower than 12 pA/√(f). Using a 1.3 μm DFB laser as the transmitter, at a data rate of 4 Gbit/s, the measured receiver sensitivity is −25.5 dBm with a bit-error-rate of 1 × 10−9. A set of two of such receivers has also been tested in a 1.3 μm polarisation-insensitive optical preamplifier system experiment. The measured receiver sensitivity, including an optical insertion loss of 1.5 dB, is −29.3 dBm.
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GaAs MIS structures with SiO2 using a thin silicon interlayer
  • Author(s): G.G. Fountain ; S.V. Hattangady ; D.J. Vitkavage ; R.A. Rudder ; R.J. Markunas
  • Source: Electronics Letters, Volume 24, Issue 18, p. 1134 –1135
  • DOI:  10.1049/el:19880771
  • Type: Article
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  • p. 1134 –1135 (2)
    The introduction of a pseudomorphic Si interlayer, about 1.0 nm thick, is found to dramatically improve the MIS characteristics of the SiO2/GaAs system. Quasistatic and high-frequency capacitance/voltage (C/V) data from such a novel capacitor structure on n-GaAs indicate that the surface of the GaAs is swept from inversion to accumulation. X-ray photoelectron spectroscopy and ion scattering spectroscopy confirm the presence of the Si layer and its complete coverage of the GaAs surface. The Si layer minimises the formation of any detrimental native oxides and thus controls the chemical nature of the GaAs surface. This approach has implications in the development of metal-insulator-semiconductor systems in general.
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Efficient operation of an Yb-sensitised Er fibre laser at 1.56 μm
Propagation modelling in the troposphere: parabolic equation method
Simple stereo algorithm for 3D positioning of object points
Novel wavelength-resonant optoelectronic structure and its application to surface-emitting semiconductor lasers
  • Author(s): M.Y.A. Raja ; S.R.J. Brueck ; M. Osiński ; C.F. Schaus ; J.G. McInerney ; T.M. Brennan ; B.E. Hammons
  • Source: Electronics Letters, Volume 24, Issue 18, p. 1140 –1142
  • DOI:  10.1049/el:19880775
  • Type: Article
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  • p. 1140 –1142 (3)
    An optimised design for optoelectronic devices which depends on the interaction between an electromagnetic standing wave and the carrier population is described. The structure consists of quantum well layers spaced at one half the wavelength of a selected optical transition in quantum wells. This spatial periodicity allows the amplifying or absorbing medium (quantum wells) to coincide with the peaks of the standing wave optical field in the Fabry-Pérot cavity. In such a periodic medium, the gain or absorption for the selected wavelength is enhanced by a factor of two compared to a uniform medium. This concept was applied to fabricate a surface-emitting semiconductor laser in the GaAs/AlGaAs system. Lasing was achieved with the shortest gain medium length (320 nm) ever reported.
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Polarisation independent switch and polarisation splitter employing Δβand ΔK modulation
Monolithic GaInAs/InP photodetector arrays for high-density wavelength division multiplexing (HDWDM) applications
  • Author(s): W.S. Lee ; S.W. Bland ; A.J. Robertson
  • Source: Electronics Letters, Volume 24, Issue 18, p. 1143 –1145
  • DOI:  10.1049/el:19880777
  • Type: Article
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  • p. 1143 –1145 (3)
    Monolithic arrays of interdigitated GaInAs/InP photodetectors have been fabricated for high density wavelength division multiplexing (HDWDM) applications. The detectors typically exhibit a reverse leakage current of 400 nA, capacitance of less than 70 fF and a responsivity of 0.5 A/W at −5 V bias. An optical crosstalk of −33.4 dB has been measured between adjacent detectors in an experimental grating demultiplexer system. Preliminary electrical crosstalk measurements in the frequency range of 1–500 MHz indicate signal isolation of the order of 46 dB.
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Integrated directional couplers with photodetectors by hydride vapour phase epitaxy
  • Author(s): S. Chandrasekhar ; J.C. Campbell ; F.G. Storz ; A.G. Dentai ; C.H. Joyner ; G.J. Qua ; T.J. Bridges
  • Source: Electronics Letters, Volume 24, Issue 18, p. 1145 –1146
  • DOI:  10.1049/el:19880778
  • Type: Article
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  • p. 1145 –1146 (2)
    The hydride vapour-phase-epitaxial crystal growth technique has been used to realise integrated waveguide-photodetectors and, for the first time, integrated directional coupler-photodetectors for detection in the 1.3μm to 1.55μ wavelength range. The GaInAsP waveguides which formed the directional couplers had propagation losses of 2 ± 0.5d B/cm and more than 90% of the guided light was coupled into the photodetectors. The directional couplers were symmetric with respect to the launch port and had 3dB coupling lengths of about 1.45 mm.
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Novel mass-fabrication of fibre couplers using arrayed fibre ribbons
  • Author(s): I. Yokohama ; K. Chida ; H. Hanafusa ; J. Noda
  • Source: Electronics Letters, Volume 24, Issue 18, p. 1147 –1148
  • DOI:  10.1049/el:19880779
  • Type: Article
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  • p. 1147 –1148 (2)
    To achieve high productivity and high density packaging of fibre couplers for practical systems, a novel mass-fabrication process using arrayed fibre ribbons has been developed. The fabricated arrayed-fibre coupler consists of four couplers which are all fabricated together from four-fibre ribbons. Each fibre coupler had 3 dB coupling ratio to within 49.3 ± 2.1%. It has been confirmed that plural fibre couplers with equal coupling ratio can be simultaneously fabricated by the mass-fabrication process.
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Combining fast DPCM compression of pictures with tree encoding
Computer analysis of finite planar arrays of circular multimode horns
Direct timing extraction in a modified-Manchester coded picosecond optical pulse fibre optic transmission system
1×2 optical switch for WDM transmission systems
Electronic compensation of saturation-induced crosstalk in optical amplifiers
Microstrip transmission line excitation of dielectric resonator antennas
Optical amplification in a multichannel FSK coherent system
Performance of a frequency-locked 1.3μm DFB laser under 50Mbit/s FSK modulation
  • Author(s): Y.C. Chung ; R.W. Tkach ; A.R. Chraplyvy ; C.B. Roxlo
  • Source: Electronics Letters, Volume 24, Issue 18, p. 1159 –1160
  • DOI:  10.1049/el:19880787
  • Type: Article
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  • p. 1159 –1160 (2)
    A GaInAsP DFB laser modulated with a 50 Mbit/s pseudorandom AMI FSK signal was locked to the 2p10−3d5 transition of argon at 1.2960μm using the optogalvanic effect. No significant degradation in frequency stability due to the modulation was observed. When the signal was demodulated, the power penalty due to the frequency-locking servo loop was found to be less than ⅓dB.
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1.56 μm Yb-sensitised Er fibre laser pumped by diode-pumped Nd:YAG and Nd:YLF lasers
  • Author(s): G.T. Maker  and  A.I. Ferguson
  • Source: Electronics Letters, Volume 24, Issue 18, p. 1160 –1162
  • DOI:  10.1049/el:19880788
  • Type: Article
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  • p. 1160 –1162 (3)
    We describe the performance of a highly efficient Yb: Er single-mode fibre laser operating at 1.56 μm. This laser has been pumped using miniature Nd : YAG and Nd : YLF lasers operating at 1.064 μm and at 1.053 μm, respectively, each of which was pumped using a 500 mW laser diode. At 1064 μm (1.053 μm) the fibre laser showed a launched threshold and slope efficiency of 13.5mW (8.5mW) and 3 1% (5.0%), respectively, with a total power output at 1.56 μm of 0.75mW (0.33mW).
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Bevelled-microlensed taper connectors for laser and fibre coupling with minimal back-reflections
Performance analysis of stop-and-wait arq schemes with compound detection
Analysis of radiation characteristics of NRD guide leaky-wave antenna by spatial network method
Radiation performance of PCVD SM fibres
Power spectral density of M-ary CPSK signals transmitted through nonlinear channels using an RF lineariser
Evaluation of HF multipath propagation effects on a novel data transmission scheme
Some designs and a characterisation method for GaAs operational amplifiers for switched-capacitor applications
  • Author(s): C. Toumazou  and  D.G. Haigh
  • Source: Electronics Letters, Volume 24, Issue 18, p. 1170 –1172
  • DOI:  10.1049/el:19880795
  • Type: Article
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  • p. 1170 –1172 (3)
    A differential to single-ended convertor stage suitable for N-channel depletion-mode GaAs MESFET implementation is modified to allow increased gain. This enhanced input stage is combined with two different high-gain stages to yield two operational amplifier designs suitable for switched capacitor applications. A new procedure for characterising amplifiers in terms of settling time is presented and applied to the above designs. It reveals the ultimate speed limitation for a given amplifier design and allows the MESFET gate widths to be scaled to obtain optimum settling behaviour for any given capacitative load.
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Line-narrowing of injection lasers due to Rayleigh backscattering from optical fibre ring interferometer
Extended-range interferometry using a coherence-tuned, synthesised dual-wavelength technique with multimode fibre links
Reliability of λ/4-shifted DFB lasers fabricated on a mass-production basis
Simplified realisation method of modified spatial smoothing technique
Wideband direct-coupled differential amplifiers utilising AlGaAs/GaAs HBTs
VLSI architecture for high-speed rank and median filtering
Small-signal impedance of GaAs-AlxGa1−x as resonant tunnelling heterostructures at microwave frequency
High-power and fundamental-mode oscillating flared sba lasers
New synthetic high coding using edge sharpening
  • Author(s): S.-H. Jung  and  N.-C. Kim
  • Source: Electronics Letters, Volume 24, Issue 18, p. 1183 –1184
  • DOI:  10.1049/el:19880804
  • Type: Article
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  • p. 1183 –1184 (2)
    A new synthetic high coding is presented for high data compression. In this scheme, only the lowpass image is transmitted, which is composed of the low-frequency components of an image, through subsampling and adaptive transform coding (ATC). Then it is expanded by interpolation at the receiver. The highpass image is simply synthesised without any overhead information by edge-sharpening the expanded lowpass image. The result of the proposed scheme shows acceptable image quality even at a high compression ratio of about 30:1
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Novel design of wide-angle single-mode symmetric y-junctions
Temperature and carrier injection-dependent characteristics of bulk unipolar (barrier) switches
  • Author(s): A. Al-Bustani
  • Source: Electronics Letters, Volume 24, Issue 18, p. 1185 –1187
  • DOI:  10.1049/el:19880806
  • Type: Article
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  • p. 1185 –1187 (3)
    The current/voltage characteristics of two-state homojunction barrier devices between 270 K and 330 K were investigated. Two new gated regenerative switching devices (the gated camel switch and the gatedpplane barrier switch) are introduced for the first time. Carrier injection-dependent operational parameters, including switching voltageVsw, switching current densityJsw, holding voltageVHand holding current densityJHwere studied. It is found that with increasing the injected electron or hole current density,Vswdecreases whileJswincreases. The two holding point parametersVHandJHremain constant over the carrier injection range. A comparison between theoretical and available experimental results is also presented.
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Attenuation in melting layer of precipitation
Reflector antenna distortion compensation by array feeds: an experimental verification
  • Author(s): Y. Rahmat-Samii
  • Source: Electronics Letters, Volume 24, Issue 18, p. 1188 –1190
  • DOI:  10.1049/el:19880808
  • Type: Article
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  • p. 1188 –1190 (3)
    Reflector antennas are subject to surface distortions which may result from thermal or gravitational effects. Surface distortions degrade antenna performance by reducing gain and introducing high sidelobe levels. In the letter, results of an experimental study have been presented to demonstrate how effectively a properly excited array feed in the focal plane of the reflector antenna can compensate for the undesirable effects of slowly varying surface distortions. The applicationof the array compensation concept could prove to be very useful for future large space or ground antennas.
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Observation of intrinsic bistability in resonant tunnelling devices

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