摘要:

Low leakage current Ga1−xInxAspinphotodiodes have been fabricated on GaAs substrates by incorporating an GaAs/Ga1−xInxAs superlattice buffer to accommodate the lattice mismatch. Devices fabricated from Ga0.65In0.35As on n+substrates exhibited leakage currents below 1 nA at −10 V, and external uncoated quantum efficiencies of ∼47% at 1.15 μm. A growth and processing sequence for fabricating devices in recesses on semi-insulating GaAs substrates with a coplanar geometry, to allow subsequent GaAs circuit processing, has been identified, and shown not to introduce a significant leakage penalty.

DOI:10.1049/ip-j.1988.0002

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Design and lasing characteristics of λ=1.3 μm GaInAsP twin-stripe (TS) metal-clad ridge-waveguide lasers, with a varying degree of index guiding between the channels are reported. The TS devices operate stably in the TE polarised mode, even if under single-stripe injection TM polarisation is observed. Effective longitudinal mode selectivity has been obtained for the TS lasers with an effective index step in the range of 1×10−2to 5×10−3between the channels. This mode selectivity can be explained by assuming coupling of lateral modes of the twin waveguide structure via the common gain-medium.

DOI:10.1049/ip-j.1988.0003

出版商:IEE    

年代:1988

数据来源: IET

摘要:

By enclosing a completely circular waveguide, of mean radius of curvatureRcwithin a surface of referenceSon which the electric field is assumed to be known, and using accurate Green's functions which take account of the planar air/dielectric (or similar) strong dielectric discontinuity, a new scalar curvature loss formula of Huygens-type is produced. The formula bridges the gap between the familiarRc−1/2-and-exponential variation of the attenuation coefficient for space waves and the less familiarRc−3/2-and-exponential variation. The methodology also separates the surface and space wave losses and reduces to existing formulas under appropriate circumstance. Numerical results are presented for a rib waveguide. These indicate that (a) surface wave loss can greatly increase the curvature loss (b) the presence of a strong planar dielectric discontinuity helps to reduce the space wave loss. The results are in good agreement with experiment.

DOI:10.1049/ip-j.1988.0004

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Ring-waveguide and pill-box structures down to 12 μm in diameter, made in GaAs/GaAlAs heterostructure material, have been designed with output stripe waveguides coupled to the rings via Y-junctions. The waveguides were defined by reactive ion etching, although the inner boundaries of some of the ring waveguides relied on stress and carrier confinement. Lasing has been observed with pulsed drive current, and has been shown to correspond to resonances in the rings, although other resonances have been observed in some of the structures. This type of structure is suitable for use as a light source in monolithic integrated optics.

DOI:10.1049/ip-j.1988.0005

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The paper reports on the optical switching operation of four contact twin-stripe injection lasers. Both directional coupling and cross coupling action have been demonstrated. Bistability involving a switch in the optical filament, between a cross coupled optical mode and a straight pass one, has also been observed. Electrical triggering of the bistable mechanism and optical switching between bistable states have been achieved with rejection ratios of up to 8:1.

DOI:10.1049/ip-j.1988.0006

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Hysteresis has been observed in the light-current characteristics of inhomogeneously pumped GaAs/AlGaAs laser diodes with both MQW and bulk GaAs active layers. Bistable action was observed in both types of device, at switching speeds suggesting that electronic mechanisms were responsible for saturation of the absorption in the passive region of each structure. In the MQW case, the wavelength of operation of the device suggested saturation of the excitonic absorption.

DOI:10.1049/ip-j.1988.0007

出版商:IEE    

年代:1988

数据来源: IET

摘要:

In the work, analytic expressions describing the behaviour of a strongly saturated nonlinear optical amplifier are deduced. These expressions make possible the calculation of the mean and variance of the amplified light photon number. Results are compared with those obtained by the numerical resolution of the photon density matrix equation, and good accordance is observed in the strong saturation regime. The results numerically obtained enable us to make conclusions about the statistical fluctuations of the optical power at the nonlinear optical amplifer output.

DOI:10.1049/ip-j.1988.0008

出版商:IEE    

年代:1988

数据来源: IET

摘要:

An alternative theoretical treatment for electro-absorption at the fundamental absorption edge of semiconductors is compared with experimental results in high purity MOCVD grown GaAs. For the first time, acceptable agreement between theory and experiment is demonstrated for wide ranges of wavelengths (0.85–1.0 μm), and applied fields (up to the breakdown field). It is shown that these results enable optimised electroabsorption modulators to be designed for low insertion loss, high extinction ratio, high cut off frequency, and wide optical bandwidth. The feasibility of waveguide device with performance parameters higher than any reported to date (with or without the use of quantum wells) is predicted, and experimental devices are reported which approach these predictions at low frequencies of operation.

DOI:10.1049/ip-j.1988.0010

出版商:IEE    

年代:1988

数据来源: IET

摘要:

A nonlinear mixing effect has been predicted theoretically, and measured using a GaInAs PIN photodiode. The nonlinear effect has been simulated using a small signal finite difference model. The variation of the effect has been measured over the frequency range 1.2–15 GHz for a number of bias voltages from 5 to 20 V, and the effect has been shown to be optoelectronic in origin. A high frequency heterodyne experiment has been performed with the optical and local oscillator signals in the range 10–20 GHz. The difference beat frequency was observed at 500 MHz and 2 GHz. The measured conversion loss was between 27 and 40 dB for a 0 dBm local oscillator signal. The application of the optoelectronic mixing effect to optical fibre frequency domain multiplex systems for the dissemination of frequency standards has been considered.

DOI:10.1049/ip-j.1988.0011

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The heterojunction phototransistor (HPT) has applications as an optical detector/amplifier in receivers for fibre optic communications systems. It is well known that the provision of an external bias, either optically or electrically, via a third (base) terminal, can enhance the performance of the HPT in terms of gain, speed of response and signal to noise ratio. This is due principally to an increase in emitter efficiency and a reduction in theRCtime constant of the emitter base junction. In the paper we show that crowding of the bias current and the signal current can affect very significantly the high frequency performance of phototransistors and will limit the advantage given by the external bias in three-terminal devices but improve the performance of two-terminal devices. The implications for the design of high speed phototransistors are discussed.

DOI:10.1049/ip-j.1988.0012

出版商:IEE    

年代:1988

数据来源: IET