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This paper presents a new design method for all-optical NAND and AND logic gates based on 3x3 general interference multimode interference (GI MMI) coupler. The whole device is realized on the silicon on insulator (SOI) platform. The transfer matrix method (TMM) and three dimensional beam propagation method (3D-BPM) are used to optimally design these devices. Key words: Optical logic gate, multimode interference (MMI) coupler, silicon on insulator (SOI), beam propagation method (BPM) | VNU Journal of Science Mathematics - Physics 26 2010 107-113 All-optical NAND and AND gates based on 3x3 general interference multimode interference couplers Le Trung Thanh Department of Telecommunication Engineering University of Transport and Communications Received 23 March 2009 Abstract. This paper presents a new design method for all-optical NAND and AND logic gates based on 3x3 general interference multimode interference GI MMI coupler. The whole device is realized on the silicon on insulator SOI platform. The transfer matrix method TMM and three dimensional beam propagation method 3D-BPM are used to optimally design these devices. Key words Optical logic gate multimode interference MMI coupler silicon on insulator SOI beam propagation method BPM 1. Introduction All-optical logic gates are important elements in photonic signal processing systems. They have many applications such as adders subtractors header recognizers parity checkers and encryption systems. In practice it is desirable to implement all-optical logic gates having small size low power consumption and high-speed 1 2 . There are many existing approaches for realizing optical logic gates. Many materials and devices have been suggested for use in optical logic. So far optical logic schemes have been mainly based on nonlinear materials 3 4 . The disadvantage of these approaches is that high optical powers are needed in order to obtain a nonlinear interaction. In addition since the nonlinear coefficient is often small long interaction lengths are generally required. Moreover devices based on nonlinear effects are not always suitable for circuit integration. Another disadvantage is that nonlinear materials are usually expensive 5-9 . A second approach for realizing optical logic is to use semiconductor optical amplifiers SOAs . SOAs are devices that amplify an optical signal without the use of optical-electrical-optical conversion 10 . Amplification is achieved in materials that exhibit optical gain.
