الفهرس 
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Abstract
Integration of photonic integrated circuits (PIC) is needed to establish a widespread affordable technique as occurred in case of electronics.Optical components such as lasers, isolators, splitter, couplers and modulator are important building blocks in photonic computational and communication. The integrated optical isolator (OI) has significant role in incorporating nonreciprocal devices onto photonic platforms such as laser diodes, laser oscillation and optical amplifiers. The goal of such devices is to prevent unwanted feedback energy from optical interfaces within a PIC back to laser sources. The back-reflections may be sources of problems include frequency instability, relaxation oscillations and additional noise which may be detrimental to optical system In this thesis, the major problems facing the development of OI in PIC will be addressed, for example bulky and integration difficulty of conventional isolator. Firstly, the variety optical isolation designs have been illustrated, and then its disadvantages have been mentioned. Further, reconfigurable unidirectional transmission based on the nematic liquid crystal (NLC) layer and 2-D photonic crystal (PhC) platforms have been presented and simulated. The suggested one way transmission can be tuned at different wavelengths based on the NLC biasing state. A comprehensive parametric study using plane wave expansion and finite difference time domain (FDTD) methods will be carried out for explaining and optimizing the performance of the proposed structure. The transmission spectra calculations reveal that the reported structure can perform nearly perfect isolation at two different bands (1406– 1412 nm and 1416–1421 nm) with an average contrast ratio (Cr) of about 36.9 dB. The investigated unidirectional PhC structure has advantages in terms of compactness and reconfigurability and can be used efficiently in ultrahigh nanoscale integrated circuits. The proposed unidirectional transmission based NLC can be exploited to implement key functionalities required in different applications such as biomedical imaging and optical communication. The thesis is composed of six chapters and can be summarized as follows: Chapter 1titled “Introduction to conventional Optical isolator illustrates the conventional optical isolator types.Chapter 2 titled ”Unidirectional Easily Integrated Transmission Devices ”illustrates an overview of the most common unidirectional easily integrated transmission devices. In Chapter 3: ”Liquid Crystal and Its Application” the classifications of LCs phases are first introduced. Next, optical designs based on PhC platform with NLC layers are discussed. In Chapter 4: ”Numerical Techniques” provides a general discussion on the numerical Techniques used to analyze the optical isolator designs. These techniques are finite difference time domain (FDTD) and plane wave expansion (PWE). In Chapter 5: ”Reconfigurable Unidirectional PC Using Liquid Crystal Layer” introduces the proposed design for reconfigurable unidirectional PC using liquid crystal layer. In Chapter 6”Conclusion and Future Work” a conclusion and future work for this thesis are presented.