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Phase-reversal travelling-wave optical modulators for broadband and bandpass applications

Watson, Christopher David; (1992) Phase-reversal travelling-wave optical modulators for broadband and bandpass applications. Doctoral thesis (Ph.D), UCL (University College London). Green open access


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This thesis is concerned with the analysis, fabrication, and characterisation of phase-reversal optical modulators for both broadband and bandpass applications. The operation of modulation is described together with the parameters by which optical modulators are characterised. Direct and indirect modulation are discussed. Particular attention is given to optical modulators constructed using titanium-indiffused lithium niobate technology. For these devices, the most important characteristics determining the frequency response and efficiency are studied. The technique of phase-reversal is examined as a means of artificial phase-matching. Systematic procedures for the design of phase-reversal electrode patterns are proposed. A novel class of equalising modulator is presented. A simulation of a digital lightwave system based on an equalising phase-reversal device is constructed. Transmission lines on anisotropic substrates are examined. The limitations of a quasi-static analysis are highlighted. A full-wave treatment utilising the method of lines is presented for the study of electrooptic modulators. Full-wave analysis is employed to study conventional coplanar waveguide electrooptic modulators. A new modulator structure, based on a fin line, is presented for high frequency operation. A comprehensive analysis of this structure is undertaken, including a modal analysis of a dielectric discontinuity. Designs are developed toward the demonstration of a device operating above 30GHz. A novel phase-matching technique, particularly suited to the fin line configuration, is discussed. The major processes involved in the fabrication of titanium- indiffused lithium niobate devices are briefly described. The techniques by which high speed modulators are measured are discussed, including a novel method by optical down-conversion. Experimental measurements are presented for devices operating in the frequency range 0 to 40GHz. The thesis is concluded, with suggestions for future avenues of research.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Phase-reversal travelling-wave optical modulators for broadband and bandpass applications
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Applied sciences; Optical modulators
URI: https://discovery.ucl.ac.uk/id/eprint/10113096
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