Showing papers in "Electronics Letters in 1979"
TL;DR: In this article, a very low loss singlemode fiber with a minimum loss of 0.20 dB/km at a wavelength of 1.55 μm is attained; this loss reaches the ultimate lower loss limit of silica-based optical glass fibre.
Abstract: A very low loss single-mode fibre with a minimum loss of 0.20 dB/km at a wavelength of 1.55 μm is attained; this loss reaches the ultimate lower loss limit of silica-based optical glass fibre. The loss mechanism is also discussed.
644 citations
TL;DR: In this paper, the characteristics of an insulated-gate field effect transistor made from amorphous silicon (a-Si) deposited in a glow discharge are discussed, and it is suggested that the a-Si device could be applied with advantage in an addressable matrix of a liquid-crystal display panel.
Abstract: The characteristics of an insulated-gate field-effect transistor made from amorphous silicon (a-Si) deposited in a glow discharge are discussed. It is suggested that the a-Si device could be applied with advantage in an addressable matrix of a liquid-crystal display panel.
362 citations
TL;DR: In this article, the authors present a ray model showing that this dependence is due to interference between a narrow bundle of axial rays and rays associated with the leaky Rayleigh wave excited on the surface.
Abstract: The output voltage of the reflection acoustic microscope depends on the location on the object surface in a way that is characteristic of its elastic properties. We present a ray model showing that this dependence is due to interference between a narrow bundle of axial rays and rays associated with the leaky Rayleigh wave excited on the surface.
218 citations
TL;DR: In this paper, an analysis of the propagation characteristics shows that there is a point below the higher-mode cutoff where the difference in group velocities between the two fundamental modes is zero but where there is large enough difference in the phase velocity to preserve polarisation.
Abstract: Elliptically cored fibres with large index differences have been drawn and shown to hold polarisation well, the modal beat length being less than 1 mm. An analysis of the propagation characteristics shows that there is a point below the higher-mode cutoff where the difference in group velocities between the two fundamental modes is zero but where there is a large enough difference in the phase velocities to preserve polarisation.
194 citations
TL;DR: In this article, a mixed method is proposed for finding stable reduced-order models using the Pade approximation technique and the Routh-Hurwitz array, which guarantees stability of the reduced model when the original system is stable.
Abstract: A mixed method is proposed for finding stable reduced-order models using the Pade approximation technique and the Routh-Hurwitz array. This method guarantees stability of the reduced model when the original system is stable.
135 citations
TL;DR: In this article, the authors have designed and fabricated singlemode silica fibres that have zero chromatic dispersion within the 1.5-1.6 μm low-loss spectral region by controlling their waveguide dispersion and dopant-dependent material dispersion.
Abstract: We have designed and fabricated single-mode silica fibres that have zero chromatic dispersion within the 1.5-1.6 μm low-loss spectral region by controlling their waveguide dispersion and dopant-dependent material dispersion. These fibres have small core diameters and large core-cladding refractive-index differences, n = 0.018, corresponding to a 13 mole % GeO2 dopant concentration in the core. The zero-dispersion wavelength was shifted from -0 = 1.375 = to =0 = 1.54 = by decreasing the fibre core diameter from 7 μm to 4.8 μm. This ability to tailor the minimum dispersion wavelength to the ultra-low-loss region near 1.55 μm is important for designing single-mode fibres for very long distance and very high capacity optical transmission.
129 citations
TL;DR: Experimental results show that, by using these techniques, bandwidth in excess of 16 times those of alumina microstrip antennas can be obtained, at the expense of an increase in the overall antenna height.
Abstract: Novel multilayer concepts for the formation of efficient micro-strip antennas on alumina substrates that allow simple antenna/circuit integration to be achieved are described. Experimental results show that, by using these techniques, bandwidth in excess of 16 times those of alumina microstrip antennas can be obtained, at the expense of an increase in the overall antenna height.
87 citations
TL;DR: In this paper, a technique for measuring the properties of deep states which trap minority carriers in the depletion region of a Schottky barrier is described, which enables states to be separated according to their capture cross-sections as well as their emission properties.
Abstract: A technique for measuring the properties of deep states which trap minority carriers in the depletion region of a Schottky barrier is described. By combining minority-carrier capture and d.l.t.s. the method enables states to be separated according to their capture cross-sections as well as their emission properties. Results on GaP are described.
84 citations
TL;DR: Biquadratic circuits are introduced which enable the exact design of switched-capacitor filters using the bilinear z-transform, and meet their specifications up to and including one-half the sampling frequency.
Abstract: Biquadratic circuits are introduced which enable the exact design of switched-capacitor filters using the bilinear z-transform. The resulting filters are completely insensitive to stray capacitances, and meet their specifications up to and including one-half the sampling frequency.
84 citations
TL;DR: In this paper, a gate structure for power thyristors using the m.o.s. field effect to control the anode breakover voltage was described, and the gate was fabricated using a V-groove etched in (100) oriented wafers and forming the gate in these grooves.
Abstract: A new gate structure is described for power thyristors which uses the m.o.s. field effect to control the anode breakover voltage. Experimental devices have been fabricated using a V-groove etched in (100) oriented wafers and forming the gate in these grooves. Both enhancement- and depletion-mode devices have been demonstrated.
83 citations
TL;DR: AlGaAs d.h.c. bias was demonstrated to be quite feasible for generation of a train of 30 ps optical pulses at a modulated frequency of below the GHz range.
Abstract: AlGaAs d.h. lasers with relatively low d.c. bias were demonstrated to be quite feasible for generation of a train of 30 ps optical pulses at a modulated frequency of below the GHz range. The pulse envelope width was measured by an s.h.g. correlation method as well as an ultrafast streak camera; the results agreed fairly well.
TL;DR: In this paper, the relative effects of core ellipticity and stress-induced birefringence on fiber polarisation properties were investigated and it was found that a reduction in core stress levels is necessary to obtain low-birefurringence fibres.
Abstract: An investigation of the relative effects of core ellipticity and stress-induced birefringence on fibre polarisation properties is described. It is found that a reduction in core stress levels is necessary to obtain low-birefringence fibres. A fibre having a retardation of only 2.6°/m is reported.
TL;DR: In this article, the phase difference between the two polarisation states of the fundamental mode on a slightly elliptical, weakly guiding fibre is derived using both an exact analysis and perturbation theory.
Abstract: The phase difference between the two polarisation states of the fundamental mode on a slightly elliptical, weakly guiding fibre is derived using both an exact analysis and perturbation theory. Deficiences in some earlier calculations are also discussed.
TL;DR: In this article, a multireflection multi/demultiplexer using interference filters is proposed, where light waves of different wavelengths are combined or separated while they propagate between two filter arrays.
Abstract: A multireflection multi/demultiplexer using interference filters is proposed. Light waves of different wavelengths are combined or separated while they propagate between two filter arrays. The insertion loss of the 6-channel demultiplexer was around 1dB.
TL;DR: In this article, the temperature dependence of threshold for InGaAsP d.h. lasers with wavelengths from 1.23 to 1.53?m was investigated and it was shown that a recombination center, rather than carrier leakage, is responsible for the temperature sensitivity of the thresholds.
Abstract: We report the temperature dependence of threshold for InGaAsP d.h. lasers with wavelengths from 1.23 to 1.53 ?m. Our results suggest that a recombination centre, rather than carrier leakage, is responsible for the temperature sensitivity of the thresholds.
TL;DR: In this article, a low-loss optical-fibre network system for monitoring air pollution and species concentrations in various environments utilising the differential absorption method is proposed and discussed as a sensitive and economical as well as nonhazardous method.
Abstract: A low-loss optical-fibre network system for monitoring air pollution and species concentrations in various environments utilising the differential absorption method is proposed and discussed as a sensitive and economical as well as nonhazardous method. Its feasibility and advantages are also described on the basis of the present state of the art of the relevant technology.
TL;DR: In this article, nonalloyed ohmic contacts to n-GaAs with contact resistances (ρc) below 1·0×10−7 Ω cm2 have been obtained using a Ge/GaAs heterojunction system.
Abstract: Nonalloyed ohmic contacts to n-GaAs with contact resistances (ρc) below 1·0×10−7 Ω cm2 have been obtained using a Ge/GaAs heterojunction system. Metals are evaporated on heavily arsenic-doped germanium (Ge) layers grown on GaAs. Low values of ρc result from the low Schottky barrier height (≈ 0·50 eV) and the high doping levels obtainable for n-Ge(≈ 1020 cm−3).
PARC1
TL;DR: Biconically tapered fiber-optic star couplers with up to 100 fiber channels were reported in this paper. But the insertion losses were not as low as −0.56 dB and the normalised standard deviations of output poers as high as 4.4%.
Abstract: Biconically tapered fibre-optic star couplers with up to 100 fibre channels are reported which have excess insertion losses as low as −0.56 dB and normalised standard deviations of output poers as low as 4.4%
TL;DR: In this paper, a new approach to the design of s.s.b. transmitters is proposed based on the generation of r.f. energy at channel frequency and the use of a feedback control system to regulate the output spectrum of the transmitter.
Abstract: A new approach to the design of s.s.b. transmitters, which overcomes the problems of the present-day transmitters, is proposed. This is based on the generation of r.f. energy at channel frequency and the use of a feedback control system to regulate the output spectrum of the transmitter so that it approximates arbitrarily closely to that of a low-level s.s.b. signal generated in a conventional way. The principles of design are applicable to all frequencies and power levels, and also readily adaptable to other modes of modulation.
TL;DR: In this paper, the design of zero-dispersion singlemode silica fiber in the ultimate minimum-loss wavelength region of the 1.5 μm wavelength is presented; the method used is the mutual cancellation of the material and waveguide dispersion.
Abstract: The design of zero-dispersion single-mode silica fibre in the ultimate-minimum-loss wavelength region of the 1.5 μm wavelength is presented; the method used is the mutual cancellation of the material and waveguide dispersion. The baseband frequency response in the wavelength region is discussed by taking the core elliptical deformation into account.
TL;DR: In this article, a GaAlAs laser is modelocked by gain modulation, and 60 ps coherent pulses are obtained at a repetition frequency of 433 MHz, at a constant number of pulses per second.
Abstract: A c.w. GaAlAs laser is modelocked by gain modulation. 60 ps coherent pulses are obtained at a repetition frequency of 433 MHz.
Abstract: The waveguide and material dispersion are investigated for various silica-based single-mode optical fibres with arbitrary refractive-index profiles. It is shown that in the case of the doubly clad optical fibre with an index difference between the core and the outer cladding Δ1=1% and that between the inner cladding and the outer Δ2=−1%, the diameter of the core 2a=7.2 μm, and the thickness of the inner cladding t=0.3a, the total dispersion is reduced within ± 1 ps/km/nm over a wide spectral range of λ=1.35–1.67 μm.
TL;DR: In this paper, N-channel enhancement and light depletion modes were fabricated on laser-annealed 0.5 μm polysilicon films, deposited on 1 μm of SiO2 grown on single-crystal silicon substrates.
Abstract: N-channel-enhancement and light-depletion-mode m.o.s.f.e.t.s have been fabricated on laser-annealed 0.5 μm polysilicon films, deposited on 1 μm of SiO2 grown on single-crystal silicon substrates. Threshold voltages of 0.35–0.45 V and −0.5 – −0.7 V and surface mobilities of 170 cm2/Vs and 215 cm2/Vs were obtained on the enhancement and depletion devices, respectively. These results compare favourably with values realised in silicon-on-sapphire (s.o.s.) and bulk N-m.o.s. devices. In addition, the measured source-drain leakage currents match the best reported values for s.o.s. devices.
TL;DR: In this paper, the combined effects of composite material dispersion, profile and waveguide dispersion can be made zero at a wavelength which depends on core diameter and refractive-index profile and composition.
Abstract: The combined effects of composite material dispersion, profile and waveguide dispersion can be made zero at a wavelength which depends on core diameter. refractive-index profile and composition. Wide bandwidths over large repeater spacings are therefore possible although close fabrication tolerances may be required.
TL;DR: In this paper, a single-mode c.w. operation at = 1.55 μm has been achieved in ridge-wavelength laser fabricated using InGaAsP quaternary alloys.
Abstract: Single-mode c.w. operation at =1.55 μm has been achieved in ridge-wavelength lasers fabricated using InGaAsP quaternary alloys. These lasers are promising candidates for future long-distance optical communications systems.
TL;DR: In this paper, a comparison between various approximations for the phase delay between orthogonally polarised modes in elliptical optical fibres is made, and a more accurate analysis is presented which gives a lower value for the birefringence produced by a given ellipticity.
Abstract: A comparison is made between various approximations for the phase delay between orthogonally polarised modes in elliptical optical fibres. A more accurate analysis is presented which gives a lower value for the birefringence produced by a given ellipticity. The effect on fibre bandwidth is shown to be small compared with that resulting from stress birefringence.
TL;DR: The contact resistivity of Au-Ge contacts on n-type GaAs was reduced by about one order of magnitude by replacing the usual Ni top layer with an SiO 2 layer.
Abstract: The contact resistivity of Au-Ge contacts on n-type GaAs was reduced by about one order of magnitude by replacing the usual Ni top layer with an SiO 2 layer. Surface coverage and edge definition of the contact areas can be optimised by proper choice of process parameters, making this technology suitable for submicrometre device processing.
TL;DR: In this article, a metal-insulator-semiconductor field effect transistors (m.i.f.t.s) have been fabricated using c.c.v.d.
Abstract: InP metal-insulator-semiconductor field-effect transistors (m.i.s.f.e.t.s) have been fabricated using c.v.d. Al2O3 as the gate insulator and the sulphur-diffusion process for source and drain. The n-channel inversion-mode device exhibits normally off behaviour. A maximum d.c. transconductance gm of 10 mS (87 mS/mm of gate width) has been obtained.
TL;DR: In this article, a GaAs-GaAlAs stripe-geometry laser with an appreciably simplified fabrication process is described, which achieves low threshold current densities even for very narrow stripe widths.
Abstract: A new type of GaAs-GaAlAs stripe-geometry laser with an appreciably simplified fabrication process is described. Owing to the excellent lateral current confinement of this structure, low threshold current densities are achieved even for very narrow stripe widths. In addition, the built-in passive wave-guiding stabilises the fundamental horizontal transverse mode, thereby avoiding nonlinearities in the light output against current characteristic. For 3?m wide and 175 ?m long lasers, threshold currents of 30?35 mA are achieved and stable transverse and longitudinal monomode emission has been observed up to more than 5 mW light power output.
TL;DR: In this paper, it was shown theoretically and experimentally that the variations of the d.c.t. and dynamic properties in a GaAs f.t when a light beam strikes the transistor's gate can be accounted for by an appropriate change in the gate-junction equivalent built-in voltage.
Abstract: It is shown theoretically and experimentally that the variations of the d.c. and dynamic properties in a GaAs f.e.t. when a light beam strikes the transistor's gate can be accounted for by an appropriate change in the gate-junction equivalent built-in voltage. A simple relationship connects this change with the variations of the light intensity.