IEE Proceedings J (Optoelectronics)
Volume 140, Issue 3, June 1993
Volumes & issues:
Volume 140, Issue 3
June 1993
Quantum-mechanical model for realistic Fabry—Perot lasers
- Author(s): D.D. Marcenac and J.E. Carroll
- Source: IEE Proceedings J (Optoelectronics), Volume 140, Issue 3, p. 157 –171
- DOI: 10.1049/ip-j.1993.0026
- Type: Article
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A fully quantum-mechanical travelling-wave time-domain model for a Fabry—Perot laser diode is presented. Extending the powerful transmission-line techniques proposed by Lowery, the model treats both the optical field and carrier populations quantum-mechanically. The Glauber function is used to represent the field, and correct correlated carrier and field-noise sources model fluctuations. It is believed to be the first presentation of a realistic quantum model for a laser diode which includes spatial hole burning, multi-moded behaviour and photon fluctuations on a picosecond timescale, together with a quantum-mechanically correct treatment of line width and intensity fluctuations.
Effect of phase noise on the evaluation of coherence of laser beam propagating through turbid medium
- Author(s): K. Arora and T.J. Harrison
- Source: IEE Proceedings J (Optoelectronics), Volume 140, Issue 3, p. 172 –176
- DOI: 10.1049/ip-j.1993.0027
- Type: Article
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The spectral broadening or the coherence time of a laser beam travelling through a turbid dense medium can be measured with high accuracy using heterodyne techniques. However, the random amplitude and phase fluctuations in the laser source can limit the accuracy of these measurements. In this paper, the limitations due to the phase noise are investigated.
Evanescent wave coupling of whispering gallery modes of a dielectric cylinder
- Author(s): D.R. Rowland and J.D. Love
- Source: IEE Proceedings J (Optoelectronics), Volume 140, Issue 3, p. 177 –188
- DOI: 10.1049/ip-j.1993.0028
- Type: Article
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By developing a direct correspondence between a given whispering gallery mode of a dielectric cylinder and a mode of an equivalent waveguide ring resonator, the evanescent wave coupling characteristics of such modes can be simply modelled. This also allows the conditions for resonant excitation of a single whispering gallery mode to be determined. The model needs a coupled mode theory which accurately describes the coupling between a straight waveguide and a curved waveguide to be developed. This theory is checked against BPM results.
Novel broadband travelling wave light intensity modulator
- Author(s): T. Chattopadhyay ; M. Bhattacharya ; M. Nakajima
- Source: IEE Proceedings J (Optoelectronics), Volume 140, Issue 3, p. 189 –192
- DOI: 10.1049/ip-j.1993.0029
- Type: Article
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The paper analyses the possibility of realising a wideband travelling wave interferomet-ric light intensity modulator (TWILIM) using the conventional simple planar electrode geometry. The proposed modulator with all its three ports matched has an optimum signal feed location which depends upon the microwave optical ‘walkoff’ factor. The ratio (halfwave voltage/ bandwidth), which defines the figure of merit of a modulator, for the proposed modulator, is ¾ that of the conventional end fed TW modulator having identical substrate, electrode length and gap at a given wavelength of operation.
Wave propagation in integrated acoustooptical anisotropic waveguides
- Author(s): U. Hempelmann and L. Bersiner
- Source: IEE Proceedings J (Optoelectronics), Volume 140, Issue 3, p. 193 –200
- DOI: 10.1049/ip-j.1993.0030
- Type: Article
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A system of coupled scalar wave equations is derived for anisotropic inhomogeneous media. Conditions of small index gradients, par-axial propagation and moderate anisotropy are used. The equations obtained serve as a basis for a beam propagation method (BPM) algorithm in anisotropic media. The anisotropy slightly modifies the dispersion characteristics of diffused channel waveguides. The BPM algorithm is tested by application to Ti indiffused waveguides in LiNbO3, the principal axes of which are declined against the laboratory coordinate system about an arbitrary angle. Very good agreement with results obtained from a plane wave analysis is confirmed. The method is applied to a combined collinear acoustooptical waveguide with transverse and longitudinal variation of one off-diagonal element of the permittivity tensor. Coupling to radiation modes occurs for sufficiently high off diagonal elements.
Frequency modulation characteristics of three-section DBR lasers
- Author(s): T. Sphicopoulos ; A. Anastassiadou ; L. Orfanos ; C. Caroubalos
- Source: IEE Proceedings J (Optoelectronics), Volume 140, Issue 3, p. 201 –205
- DOI: 10.1049/ip-j.1993.0031
- Type: Article
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A theoretical analysis of the dynamic behaviour of a three-section DBR laser is presented. The FM response, due to the refractive index modulation resulting from injection current modulation, is studied by means of a small signal analysis. Modulation can be considered in one or more sections. A condition leading to the IM suppression, and to the elimination of relaxation oscillation of the FM response, is derived. The model is based on the transfer matrix method by means of which the whole structure can be reduced to a Fabry—Perot laser with an effective complex reflectivity depending on current modulation in the passive sections. Results for a typical example of such a structure are presented and discussed.
Orthogonality relations for the eigenmodes of lossy anisotropic waveguides (fibres)
- Author(s): A.B. Manenkov
- Source: IEE Proceedings J (Optoelectronics), Volume 140, Issue 3, p. 206 –212
- DOI: 10.1049/ip-j.1993.0032
- Type: Article
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The system of the eigenmodes propagating along an anisotropic fibre is constructed by the Ŝ-operator method. The fields of the radiation modes are shown to be unbounded at infinity in cross-section. For these modes the orthogonality relations are derived with the help of regularisation of divergent integrals. The normalising factor is demonstrated to be expressed in terms of the eigenvectors of the Ŝ-operator. The results obtained are applied to an excitation problem. The structure of the far-zone fields is analysed.
Multiplexing of fibre gyroscopes with square wave bias modulation
- Author(s): W. Jin and B. Culshaw
- Source: IEE Proceedings J (Optoelectronics), Volume 140, Issue 3, p. 213 –216
- DOI: 10.1049/ip-j.1993.0033
- Type: Article
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The principle of operation of a multiplexed fibre optic gyro system with square wave bias modulation is presented. The minimum path length difference between different gyro routes, required for demultiplexing of gyro signals, is calculated to be less than one metre for typical gyro parameters. The effect of nonideal square wave modulation is discussed and a technique designed eliminate it is presented.
Excess noise in heterodyne receivers
- Author(s): M. Schiess and B.S. Johansson
- Source: IEE Proceedings J (Optoelectronics), Volume 140, Issue 3, p. 217 –220
- DOI: 10.1049/ip-j.1993.0034
- Type: Article
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The influence of excess noise above the classical shot noise level in heterodyne receivers is investigated. It is shown how excess noise from the local oscillator (LO), beside thermal and phase noise, influences the system performance. Under carefully controlled experimental conditions, the LO power can be decoupled from excess noise. This yields an optimum LO power to get maximum receiver sensitivity. The optimum LO power is determined by the transition from shot noise dominance to excess noise dominance.
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