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Realization of All-Optical Discrete Cosine and Sine Transforms Using MMI Structures on an SOI platform

The Discrete Cosine Transform (DCT) and Discrete Sine Transform (DST) have found applications in digital signal, image and video processing and particularly in transform coding systems for data compression and decompression. Multimode interference (MMI) in optical silicon on insulator (SOI) waveguides is attractive for realizing all-optical DCT and DST transforms as they have the advantages of low loss, ultra-compact size and excellent fabrication tolerances. In this paper, a novel approach to realize all-optical type I, II, III and IV DCT and DST based on multimode interference structures on silicon on insulator platform is proposed. Based on the transfer matrix method, the analytical expressions describing the characteristics of the MMI structures are derived. Designs of the proposed devices are then verified and optimized using 2D and 3D BPM simulations.