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Design and Analysis of Optical Splitters using Subwavelength Structures in Silicon on Insulator Platform

Arik, Kamalodin | 2024

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 58313 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Akbari, Mahmood; Khavasi, Amin
  7. Abstract:
  8. Optical telecommunication has received much attention due to its high capacity in the fast transmission of information over long distances. Each optical communication system includes a light source as a transmitter, an optical detector as a receiver, and an optical waveguide as a transmission and connection medium. Optical waveguides are used in a wide group of optical devices such as couplers, modulators, sensors, lasers and optical amplifiers. For this reason, optical waveguides are one of the main components of optical circuits used to form and connect devices within communication systems. Among the waveguides, subwavelength grating waveguide as a periodic structure is of central importance in light engineering. The wide applications of such waveguides in various fields of science, including optics, electromagnetics, acoustics and communications, reveal the importance of strong tools for accurate and reliable analysis of these waveguides. As the first goal, in order to circumvent issues related to numerical instability, slow convergence, high computational cost, low generality and the complexity of root finding of the dispersion equation, corresponding to conventional modal analysis methods, we establish a new method based on the expansion of electromagnetic fields in terms of Legendre polynomials for dielectric optical waveguides, especially periodic structures. By expanding electromagnetic fields in terms of Legendre polynomials and applying appropriate boundary conditions, the problem is solved in the complete space covered by orthogonal Legendre polynomials. The scope of application of the presented method is the modal analysis of periodic and non-periodic dielectric optical waveguides, and stratified waveguide structures with homogeneous and (or) heterogeneous layers. The advantages of the proposed method are: 1) Expansion of continuous and smooth functions on a bounded interval in fast-converging series in terms of well-behaved Legendre polynomials 2) the possibility of close root finding due to the algebraic behavior of the dispersion equation of the proposed method 3) without the problem of numerical instability due to the absence of very large or (and) too small numbers in the constituent matrices of the dispersion equation which can be originated from the fact that our solution region is limited. As the second goal, we analyze and design an important and practical device within photonic integrated circuits in order to spatially overlap optical fields or split light from one waveguide to another waveguide(s) called optical coupler (optical power combiner or splitter). This device consists of several waveguides together. The modal analysis of such waveguides using the proposed method or any other efficient one is a pivotal aspect of the design process, shedding light on potential modes of propagation and the electromagnetic behavior of the desired optical coupler. As the third and the final goal, we propose a novel graphene-based dynamically tunable power splitter on SOI platform using the couplers designed in the previous goal. The performance of the device operation is significant over a wide range of telecommunication wavelengths
  9. Keywords:
  10. Non-Modal Analysis ; Optical Waveguides ; Power Divider ; Legendre Polynomial ; Tunable Optical Power Splitters ; Subwavelength Apertures

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