No description available.

In this thesis, passive and active 3-branch Ti:LiNbO$ sb3$ waveguide devices were investigated. A multimode field-matching technique was employed to predict the power division in a passive 3-branch waveguide power divider. The limitation and range of validity of this method were pointed out. An alternative method was also employed to predict the power division when coupling between two neighbouring branches is not negligible, as is the case when the branching angle becomes small. The multimode field-matching method was also employed to predict the power division in an active 3-branch waveguide switch, where switching is achieved through the electrooptic effect of LiNbO$ sb3$. The edge effect of the electrodes on the beam steering was also considered. A linear mode-confinement modulator was then proposed and investigated as a derivative of the 3-branch waveguide switch. / Fabrication and experimental characterization of the three devices were also carried out. Key functional parameters were measured and compared with theoretical predictions. In general experimental results have borne out theoretical prediction. / Some calibration of the fabrication techniques employed, were also performed. An outline of the various experimental techniques used is also given. / Finally, some possible improvements are suggested for further work.

No description available.

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Thesis (Ph.D.) - James Cook University, 2003. / Typescript (photocopy). Bibliography: leaves [318]-342.

The problem of electromagnetic wave propagation across the junction of two similar planar dielectric waveguides is analysed, within the Kirchhoff approximation, by expanding the field into transverse variations of all possible modes. It is proven that the expansion can represent any solution for any planar dielectric waveguide. The spectral function is introduced into the representation, and this helps resolve some of the theoretical problems in passing from the limit of closed waveguides to open waveguides. Using the spectral function and the Gel'fand-Levitan integral equation some new exact solutions to novel dielectric planar waveguides can be found. Examples of waveguiding by total internal reflection or by Bragg reflection (which are physically very different processes) can be generated by changing a single parameter in the formulation. Usually the representation for an open dielectric waveguide requires the matrix spectral function. However the Gel'fand-Levitan reconstruction is defined for scalar spectral functions. A technique for constructing the spectral matrix and the scattering solutions from two spectral functions is demonstrated. This technique uses a variational formulation of a scattering experiment. The connection between a dielectric structure and the characteristics of propagation on it is obscure. However the connection between these characteristics and the spectral function is much clearer. It is sometimes possible to make predictions about the properties of the waveguide by looking at its spectral function only. Since the connection between the spectral function and the dielectric structure is well established by inverse spectral theory, introducing the spectral function has been of help in establishing the desired connection between the dielectric structure and the characteristics of propagation on it. Such considerations suggest one of the above waveguides is sensitive to small perturbations and could be used as an electro-optic modulator. Detailed calculations confirm the hypothesis. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Thesis (M.S.)--Boston University. A travel guide and time capsule of Boston in 1952: "When a visitor comes to Boston he is handed an armful of pamphlets, maps and advertisements from which he can garner little about modern Boston. This book has included the information from all available publications and then gone much further and gives the whole and: true story and picture of Boston in 1952."

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

This dissertation describes various nonlinear grating coupling phenomena in InSb waveguides. InSb exhibits an opto-thermal, diffusive nonlinearity at 9.6μm. This nonlinearity strongly modifies the growth of a guided wave via the grating coupling of an incident, Gaussian signal. In particular, optical limiting and bistability in the coupled power were demonstrated for a detuned grating coupler. The limits on the detunings were also investigated. The experimental results showed qualitative agreement with a theory based upon a diffusive nonlinearity in the grating coupling process. Also demonstrated and theoretically explained was a new form of "butterfly" bistability in the output coupled signal from a nonlinear waveguide. In this situation, nonlinear interference effects in the substrate modified the proportion of power outcoupled into the cover and the substrate. The effects of a thermal nonlinearity on the response of a distributed feedback grating (DFB) were also studied. The DFB reflection response of an incident guided wave was modified either by varying the power of the incident guided wave or that of a second guided wave. Also, the effects of the DFB reflection were shown to enhance the bistable input grating coupling process by providing an additional feedback. This enhancement resulted in a smaller incident switching power required to obtain bistability in the input coupler.

The effect of linear absorption on TE0 nonlinear guided waves and the effect of linear absorption, input-beam misalignment and nonlinear saturation on soliton emission from a nonlinear waveguide have been numerically investigated using the beam propagation method. In the first case the distribution of the absorption is found to have a dramatic effect on the propagation of the nonlinear guided waves. In the second case results reminiscent of the lossless case are found to survive in the presence of these complications.