IEE Proceedings - Optoelectronics
Volume 147, Issue 2, April 2000
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Volume 147, Issue 2
April 2000
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- Author(s): E.M. Pratt and J.E. Carroll
- Source: IEE Proceedings - Optoelectronics, Volume 147, Issue 2, p. 77 –82
- DOI: 10.1049/ip-opt:20000284
- Type: Article
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An outline is given for one method of large signal time domain modelling of semiconductor lasers, which preserves photon–electron balance for a wide range of unknown spectral inputs by using a time domain filter in the recombination equation as well as in the field excitation equations. The gain filter has an approximately parabolic gain profile in the frequency domain, and can be implemented at each point of the laser and have its peak gain, frequency of peak gain and gain bandwidth change as the electron density changes. Some preliminary differences are examined using a recombination equation gain filter (REGF) or no REGF for large signal, time domain models of a laser amplifier and a phase shifted DFB. - Author(s): D.M. Ryan ; R.A. Abram ; D.J. Robbins
- Source: IEE Proceedings - Optoelectronics, Volume 147, Issue 2, p. 83 –88
- DOI: 10.1049/ip-opt:20000288
- Type: Article
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Asymmetric double quantum well structures with applied transverse electric field are of interest in optical modulator applications. A theoretical model of their optical properties is described. The bandstructure of the heterostructure is calculated using a k.p envelope function method. The first conduction band and the three lowest valence bands (heavy hole, light hole and spin split-off) of the bulk materials are included in the calculation, with all other bands treated as a perturbation. The method adopted to solve for the electronic states is to break the active region into a finite number of thin layers where the electrostatic potential due to the applied electric field can be taken as spatially constant and equal to the local average value. The allowed bulk states are calculated for each layer and matched at each layer interface, and at the hetero-interfaces using Burt-Foreman boundary conditions. Absorption spectra have been calculated for an InP/110 Å In0.55Ga0.45As/25 Å InP/65 Å In0.55Ga0.45As/InP structure for a range of electric fields and compared to experimental data. Absorption spectra have also been calculated for a second structure which consists of InP/60 Å In0.53Ga0.47As/20 Å InP/100 Å In0.53Ga0.47As/InP, and these results are examined in terms of light intensity modulation at a wavelength of 1.55 μm. The calculated absorption spectra show encouraging agreement with the experimentally measured photocurrent spectra for the first structure. The calculated absorption coefficient at 1.55 μm for the second structure is predicted to increase with moderate applied bias by approximately an order of magnitude, suggesting that it could form the basis of a room temperature modulator for light at that wavelength. - Author(s): T.O. Körner
- Source: IEE Proceedings - Optoelectronics, Volume 147, Issue 2, p. 89 –95
- DOI: 10.1049/ip-opt:20000293
- Type: Article
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p.
89
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The combined optical and electric simulation of a metal-semiconductor-metal (MSM) photodetector is presented. The generalised multipole technique (GMT) for rigorous modelling of the light propagation is combined with electric device simulation methods based on a drift-diffusion charge carrier transport model. Different optical designs are compared with respect to the detector performance that can be achieved. It is demonstrated that the use of incoupling gratings can significantly increase the detector efficiency, compared to designs using antireflective layers. Numerical experiments carried out for illumination under varying angles of incidence also show that not only the amount of light that reaches the semiconducting substrate but also the exact spatial intensity distribution have non-negligible effects on the detector efficiency and response times. This in turn proves the necessity of rigorous optical simulation. - Author(s): P. Öhlén and E. Berglind
- Source: IEE Proceedings - Optoelectronics, Volume 147, Issue 2, p. 97 –103
- DOI: 10.1049/ip-opt:20000289
- Type: Article
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A reshaping optoelectronic repeater is investigated in a loop experiment. If such a device is used in an optical network, the jitter accumulation and its influence on the cascadability are important issues. Whereas the RMS jitter was fairly independent for PRBS patterns, the bit-error rate showed a large pattern dependence. In order to explain these results, a simplified model of the repeater is used, where the device is modelled as a filter followed by an ideal limiter. - Author(s): C.C. Chang and K.T. Wu
- Source: IEE Proceedings - Optoelectronics, Volume 147, Issue 2, p. 104 –108
- DOI: 10.1049/ip-opt:20000287
- Type: Article
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An experimental study is presented involving the fabrication and analysis of a relatively new structure n-ZnSe/p-Si/n-Si heterojunction phototransistor having a high photo-current responsivity in the short-wavelength spectrum. Utilising photoluminescence (PL) spectroscopy and cyrosystems to investigate the optical characteristics of the grown ZnSe epilayer, the dominant emission peak was 444 nm (2.793 cV) with a FWHM of 28.3 mcV at 10 K due to near-band-edge (NBE) excitation emission. Group III element indium was selected as the n-type dopant for thermal diffusion on the ZnSe epilayer utilised to fabricate the studied device. The resulting photo-current responsivity was approximately 50 A/W at a bias voltage of VCH=15 V, with the highest photo-current responsivity occurring at a frequency of 470 nm. The study demonstrates that n-ZnSc/p-Si/n-Si heterojunction phototransistors are capable of functioning as short-wavelength photodetectors and have considerable potential in optoelectronic integrated circuit (OEIC) applications. - Author(s): C.-L. Ho ; M.-C. Wu ; W.-J. Ho ; J.-W. Liaw
- Source: IEE Proceedings - Optoelectronics, Volume 147, Issue 2, p. 109 –113
- DOI: 10.1049/ip-opt:20000283
- Type: Article
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High-speed p-end-illuminated planar InP/InGaAs/InP heterojunction p-i-n photodiodes have been fabricated with symmetrical and asymmetrical doping profiles. Static and dynamic characteristics of both devices were measured for comparison. The device with symmetrical doping profile exhibits inferior characteristics at low reverse bias (<4 V). Nevertheless, if sufficiently reverse biased (≥4 V), a symmetrically doped device can have DC responsivity comparable to, and maximum 3 dB bandwidth higher than, a conventional asymmetrically doped device. The inferior characteristics at low reverse bias and promoted maximum bandwidth of a symmetrically doped device can be, respectively, attributed to the heterointerface exposed in the depletion region and reduced device capacitance caused by an extra-depleted InP region. - Author(s): M. Karásek and A. Bellemare
- Source: IEE Proceedings - Optoelectronics, Volume 147, Issue 2, p. 115 –119
- DOI: 10.1049/ip-opt:20000286
- Type: Article
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p.
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Numerical analysis of a recently proposed multifrequency erbium-doped ring laser employing a frequency periodic filter and frequency shifter is presented. The model is based on a homogeneously broadened three-level approximation of an erbium ion. The multifrequency operation is achieved by shifting the frequency of the amplified spontaneous emission (ASE) power circulating in the ring cavity by one wavelength slot each circulation period to prevent steady-state single-frequency laser operation. The effect of cavity loss, erbium-doped fibre (EDF) gain, direction of ASE circulation on lasing spectrum uniformity and output power is investigated. - Author(s): I. Hong and H. Park
- Source: IEE Proceedings - Optoelectronics, Volume 147, Issue 2, p. 120 –122
- DOI: 10.1049/ip-opt:20000285
- Type: Article
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p.
120
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Quasi-static analysis of travelling-wave electrodes with asymmetrical finite thickness for electro-optic modulators is described. A generalised mode-matching method has been used to analyse the inhomogeneous structure with asymmetrical electrode thickness. The effects of asymmetrical electrode thickness on the effective dielectric constant and characteristic impedance of coplanar strip electrodes are discussed. Numerical computations show that asymmetrical properties of thick electrodes can improve the phase velocity mismatch between electric and optical waves in an electro-optical modulator or switch. - Author(s): E. Lea and B.L. Weiss
- Source: IEE Proceedings - Optoelectronics, Volume 147, Issue 2, p. 123 –131
- DOI: 10.1049/ip-opt:20000281
- Type: Article
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p.
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The modelling of the strain, refractive index and optical mode intensity profiles of photoelastic waveguide structures in Si1−xGex/Si heterojunctions are presented. Strain profiles due to the difference in the thermal expansion of Si1−xGex and SiNy are produced by depositing SiNy stripes on the heterostructure surface. The corresponding strain-induced refractive index changes are modelled by finite element analysis. The photoelastic constants are calculated and are used to find the strain-induced refractive index profiles in the waveguides. It is shown that these photoelastic waveguides exhibit a low degree of birefringence because they are oriented along the [100] crystal axis. Optical mode profiles are generated from finite difference calculations which show that there are three distinct guiding regions under each SiNy stressor stripe; these vary with stripe width. Experimental results show good agreement with the model, and both show that the modal characteristics of the photoelastic waveguides are determined by the SiNy stripe width. - Author(s): K. Obermann and K. Petermann
- Source: IEE Proceedings - Optoelectronics, Volume 147, Issue 2, p. 133 –137
- DOI: 10.1049/ip-opt:20000292
- Type: Article
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The transmission of the input intensity noise for wavelength converters based on cross-gain modulation in semiconductor optical amplifiers is investigated theoretically. It is shown how the noise statistics change due to the nonlinear transmission function and how bit error rates can be estimated. The power penalty strongly depends on the wavelength shift and can be 5.2 dB at 2.5 Gbit/s when the wavelength is up-shifted by 20 nm. When the extinction ratio is enhanced by the converter, even negative penalties are obtainable. In agreement with computer simulations, the input dynamic range is determined to be at least 13 dB. Furthermore, it is demonstrated that at 2.5 Gbit/s, 62 wavelength converters can be cascaded when each converter is operated so that the extinction ratio is preserved. However, when the wavelength is alternatively down-and up-shifted by 15 nm, less than eight stages are cascadable. - Author(s): S.G. Romanov ; A.V. Fokin ; H.M. Yates ; M.E. Pemble ; N.P. Johnson ; R.M. De La Rue
- Source: IEE Proceedings - Optoelectronics, Volume 147, Issue 2, p. 138 –144
- DOI: 10.1049/ip-opt:20000346
- Type: Article
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p.
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The photonic energy band structure of a 3D, face-centred cubic package of silica balls (synthetic opal) was studied for both the positive refractive index (RI) contrast (RIball>RIvoid) and inverted contrast (RIball<RIvoid) situations. The inverted situation was obtained by impregnation of interstitial voids with a high-RI semiconductor. Following the inversion of the scattering ensemble, a dramatic change in the stop-bandwidth and angular dispersion of the stop-band were observed. The spontaneous emission from an incomplete photonic crystal is anisotropic to an extent which depends on the angular dispersion of the stop-band: it is suppressed in the middle of the stop-band and amplified at the stop-band edges. The amplified spontaneous emission (ASE) regime is the result of interplay between the photonic and electronic energy bandstructures of the photonic crystal. This effect is considered to be a precursor for stimulated emission.
Gain modelling and particle balance in semiconductor lasers
Optical properties of asymmetric InGaAs/InP coupled quantum wells
Combined optical and electric simulation of metal-semiconductor-metal photodetectors
Measurements and modelling of pattern-dependent BER and jitter in reshaping optoelectronic repeaters
Fabrication of n-ZnSe/p-Si/n-Si heterojunction phototransistor using IR furnace chemical vapour deposition and its optical properties analysis
Comparison between planar InP/InGaAs/InP pin photodiodes with symmetrical and asymmetrical doping profiles
Numerical analysis of multifrequency erbium-doped fibre ring laser employing periodic filter and frequency shifter
Quasi-static analysis of travelling-wave electrodes with asymmetrical finite thickness for electro-optic modulators
Modelling and characteristics of photoelastic waveguides in Si1−xGex/Si heterostructures
Estimation of BER performance and cascadability of wavelength converters based on cross-gain modulation in semiconductor optical amplifiers
Opal-based composites as photonic crystals
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