الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Basic equations of wave optic model are used to analyze the dielectric waveguides (slab waveguide and the round optical fiber). Dielectric slab waveguide and step-index fiber are treated as a boundary value problem so that the characteristic equation describing the guided modes is developed. Linearly Polarized (LP) modes assumption is used to simplify the optical fiber exact characteristic equation. Various coupling techniques such as waveguide to waveguide couplers, planar to planar couplers, planar to linear couplers and beam to waveguide couplers are overviewed. Coupled mode approaches based on coupled mode theory (CMT) and improved coupled mode theory (ICMT) are used to analyze the coupled mode equations. The coupling is established via the evanescent part of the modal field propagating in the fiber which penetrates the slab waveguide. Coupling mechanisms in the two approaches could be derived from solving Maxwell’s equations governing the electromagnetic fields and using Lorentz’s reciprocity theorem. Coupling between the waveguides under study is represented by two coupled first order differential equations. The coupled mode equations are given for the two approaches where the coupling coefficient, output power and propagation constant difference factor are introduced for the two approaches. The coupling coefficient determines the interaction strength or the distance over which a given fractional exchange between two modes take place. The guided power exchanged between the waveguides is illustrated through the output power. The propagation constant difference measures the degree of mismatch between the propagation constants of the propagating modes which identifies codirectional coupling and contradirectional coupling between waveguides. The physical parameters of the waveguides such as refractive indices of the waveguide cores and geometrical parameters such as coupling length, thickness of substrate of slab waveguide, and distance between core of waveguides are used to study coupled mode equations. Similar coupled parallel waveguides are analyzed through using these analytical approaches. Transverse coupling between single mode fiber and single mode planar waveguide is analyzed by the ICMT and the CMT. Also, the key parameters that affect the coupling process are analyzed using the ICMT. ICMT gives superior results in coupling magnitudes over that given by CMT at weakly guiding while, at strong guiding, this difference is not censored. ICMT offers second order corrections to CMT. ICMT can provide accurate solutions for most applications of practical interest in integrated optics. Finally, ICMT could be applied to asymmetric coupled waveguides accurately.
Integrated couplers are main components in modern communication systems. High efficient coupling between optical waveguides is necessary to achieve efficient components that are used widely in the optical systems, so it is necessary to achieve selectivity and interfacing between these different components. The coupling techniques between waveguides are different, such that coupling techniques based on evanescent waves are studied using analytical approaches like Coupled Mode Theory (CMT) and Improved Coupled Mode Theory (ICMT). These coupling techniques based on overlap integrals. The coupled structures studied are coupled slab to slab, fiber to fiber and slab to fiber waveguides. ICMT provide accurate results over that achieved by CMT at low refractive index difference between results between waveguides cores and outside mediums. The coupling coefficient given by ICMT are greater than those given by CMT