Graphene-based Optical Modulator Basic Research

With the fast development of optical communication and optical interconnect, the research about integrated optical modulators with smaller footprint, larger optical bandwidth and super high modulation speed has been immediately increased. Graphene has attracted great attention throughout the world due to its extraordinary optical and electrical advantages. The modulators based on Si photonic waveguide configuration with graphene, which marry the advantages of low operation voltage, compact footprint and ultrafast modulation speed, can meet the growing demand on optical communication in the future.In this thesis, the basic theory of graphene-based electro-absorption optical modulator is discussed. Then some novel and improved graphene-based waveguide structures and their performances are proposed:1. After investigating lots of papers about optical modulators, graphene and graphene-based optical modulators, the traditional modulators’ principles and characteristics are revealed. In addition, the progress of graphene-based optical modulator in the recent years is introduced.2. The latest investigation of graphene plasmonics, photonics, and electronic properties is reviewed. Particular emphasis is focused on the capacity to combine silicon platform with grapheme photonics to afford optical modulator with high modulation speed, broadband operation and compact footprint.3. Several commonly used numerical methods for the mode analysis of waveguide are introduced, such as Finite Difference Time Domain(FDTD), Beam Propagation Method(BPM), and Effective Index Method(EIM). At the same time, modulator’s performance is discussed.4. For a high- ? dielectric spacer, a 3dB modulation was achieved with an operation bandwidth of 76 GHz and with energy consumption of 0.39 fJ bit whereas for the low- ? dielectric spacer it was found to be 250 GHz and 1.82 fJ bit respectively. A novel graphene-based vertical slot waveguide structure is proposed, and the analysis shows that the optical TE mode also can be strongly absorbed.