摘要:

The plasma etching of GaAs and InP using CH4/H2process gas is reported, and their etching characteristics as a function of platen temperature are shown. These results highlight the two different etching mechanisms for GaAs and InP. Etching of GaAs using chlorine plasma chemistry is discussed with emphasis on surface roughness and damage and then compared to the CH4/H2process chemistry which yields better etch surface characteristics.

DOI:10.1049/ip-j.1989.0002

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The modal operation of asymmetric twin ridge waveguide lasers is investigated. A regime of operation is theoretically identified where modal switching is possible. Modal bistability is observed in this regime, and shows novel properties in that it is observed to be triggered optically, and not electrically. The switching speed is limited to 5 ns, but the switching is not critically dependant on trigger wavelength.

DOI:10.1049/ip-j.1989.0003

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Formulae for dressed dynamical parameters of semiconductor lasers are derived in the general case of a nonlinear optical gain. Numerical calculations of the dynamical variation of the dressed resonance frequency and damping parameter are presented. A closed form expression for the dressed dynamical parameters is found for the case of direct sinusoidal modulation and a quasi-analytic approach to obtaining detailed features of the laser dynamics is thereby derived. Wider applications of the concepts of dressed dynamics are examined.

DOI:10.1049/ip-j.1989.0005

出版商:IEE    

年代:1989

数据来源: IET

摘要:

DFB lasers have been characterised in terms of linewidth. The effect of antireflection coating on linewidth has been measured. The frequency modulation (FM) response has been measured and the system implications of a nonflat FM behaviour are discussed. Two section DFB lasers with electro-optic tunability are described and results presented.

DOI:10.1049/ip-j.1989.0006

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The paper describes a simple circuit model for semiconductor lasers in single mode operation. This model is based on theorems well established in the microwave field, and applicable to any resonant system. A particular advantage is that, through the relationship between reflection coefficient and admittance, the same circuit, consisting only of a singleLCRresonance, can be used in a totally general way for DFB and Fabry Perot structures. In addition the shape of the spectra can be examined using Fourier techniques. Results are presented for Fabry Perot lasers which show excellent agreement with established theory. DFB lasers, both uniform devices and those with a non-corrugated phase shift section, are then examined. A general method for a phase slip DFB laser with an external cavity is presented and results shown for simple cases.

DOI:10.1049/ip-j.1989.0007

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Longitudinal mode selection in diode lasers by injection locking has been studied using the standard multimode rate equations with an optical injection term, and with the effects of spontaneous emission included. The phenomena of spectral narrowing and power switching between the dominant free-running mode and the injected target mode are illustrated and discussed. In general, injection locking into the long-wavelength side of the spectrum is more effective than into the short-wavelength side because of the gain peak shift. The relaxation oscillation frequency is estimated using a small-signal analysis of the single-mode rate equations, an approach that is valid provided the external injection is strong enough. Our calculations indicate that around the gain peak the relaxation oscillation frequency strongly depends on the wavelength of the injected target mode, because of the changing differential gain. Modes with shorter wavelengths have faster relaxation oscillations due to larger differential gain. This can be helpful in increasing the transmission speed in optical communication applications.

DOI:10.1049/ip-j.1989.0008

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Modulated transmission and reflectance measurements have been performed on a number of MOCVD grown structures of the typep+-x-n+wherexis either an undoped layer of GaAs, a GaAs doping superlattice, or a compensated layer of GaAs. The structures have been characterised byI/V,C/Vand photoluminescence measurements. For the doping superlattices, with individual layer thicknesses of between 18 and 70 nm and doping levels of 1018/cm3, the superposition of the externally applied field on the large built-in field allows very high internal fields to be applied over a limited region of the sample. In this way, fields of up to ∽500 KV/cm have been applied. For photon energies close to the bandgap of GaAs, the modulation properties of the structures are consistent with a Franz-Keldysh mechanism up to the highest internal electric fields, with no evidence for the anomalous behaviour reported elsewhere. At longer photon wavelengths, a dispersionless modulation in optical transmission is observed whose origin is related to contributions from the linear and quadratic electro-optic effects. In this regime, an anomalous dependence on optical polarisation is observed.

DOI:10.1049/ip-j.1989.0009

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Modulation characteristics of lattice-matched InGaAs-InP MQW structures containing 50 and 150 wells are compared. A contrast ratio of 2.6:1 (4.1 dB) has been attained at 1590 nm (4.9 dB insertion loss) in a 150 well sample. This is the largest perpendicular-geometry modulation reported in InGaAs-InP to date. A 46 meV quantum-confined Stark shift has been attained in an applied electric field of 2.5 × 105V/cm−1in the 50 well sample. This shift is ̃ 8 times the exciton binding energy, and is larger than any previously reported in InGaAs-InP.

DOI:10.1049/ip-j.1989.0011

出版商:IEE    

年代:1989

数据来源: IET

摘要:

We have simulated the modulation properties in transmission and reflection of an electrically active Fabry-Perot etalon containing a GaAs-AlGaAs multiple quantum wellpinstructure. The calculations are based on our measurements of room temperature electro-absorption in a nonresonant device, rather than an empirical model, and generate the optimum values of modulation for any given etalon by selection of the appropriate cavity length. It is found that improved modulation can be obtained compared to the non-resonant device, mainly due to multiple-pass electro-absorption. For example, a device with front and back mirror reflectivities of 0.3 and 0.9 respectively, and a 1 μm thick multiple quantum well structure, shows a change in reflection from about 75% to 10% at ≃865 nm when biased from 0 to −10 V. To obtain even higher changes in transmission or reflection and to utilise the electro-refractive properties of the material, high finesse cavities are needed. This however, appears to impose severe constraints on the epitaxial growth accuracy and operational stability of such devices.

DOI:10.1049/ip-j.1989.0012

出版商:IEE    

年代:1989

数据来源: IET

摘要:

A travelling optical flux analysis is carried out on a GaAs monolithic active integrated-optic waveguide (AIOW) to calculate both the nonlinearity of its static input/output characteristics and the spontaneous noise generated. From this model, the output signal-to-noise ratio of the guide, as well as its quasistatic harmonic distortion characteristics are found. Features of the model are the inclusion of the wavelength dependence of the stimulated gain and the spontaneous emission characteristics, and the variation of the carrier density and photon flux in the longitudinal direction of the waveguide. This enables the effect of the input wavelength of the light source on the transmission characteristics to be studied, as well as the output noise spectrum to be calculated under different conditions of forward path gain along the guide.

DOI:10.1049/ip-j.1989.0013

出版商:IEE    

年代:1989

数据来源: IET