Final Report Summary - MIDEX (Mid refractive Index contrast Si photonics platform for telecommunication applications) The fellow proposed to develop a Si Photonics platform based on mid-refractive index contrast optics (MiDex) of SiN and SiGe for the future dense WDM system. The fellow aims to understand the SiN/SiOxNy optical properties at optimized conditions for Dense WDM system, and develop dense and optimized WDM SiOxNy optical circuitry. Integration between GeSi optoelectronic devices and SiOxNy passive optical circuitry on bulk silicon wafer shall also be studied. During the first months of the project, the fellow learned the deposition techniques and material quality of SiNx deposited at room temperature at the University of Tokyo cleanroom (class1). Despite such low deposition temperature, material characteristics were very promising for the realization of high-performance photonic components. Subsequently, the fellow performed complex design of optical components including array waveguide grating (AWG) for the realization of WDM SiNx optical circuitry. The fellow used a combination of analytical solutions, commercial software of beam propagation method (BPM), and 3D FDTD to come up with a reliable and self-consistent design of AWG. The fellow performed device, fabrication and optical characterization of the AWG and SiNx waveguide. The fellow finished the design of an optical coupling integration between Ge-based device and SiNx waveguide. He then participated in the fabrication of a tested structure to experimentally validate the integration of a Ge-based optical detector with SiNx waveguide on ordinary Si wafer using mainly electron-beam lithography (Advantest F5112), PVD (Sputter Anelva EB1100), and CMP machine (Logitech PM5) at the University of Tokyo cleanroom. In particular, the fellow demonstrated the advantages and disadvantages of using low-temperature deposition of SiNx using a unique physical vapor deposition (PVD). This approach is new in comparison with the ones used by most of the research communities focusing on chemical vapor deposition (CVD) at usually a much higher temperature. Moreover, the fellow used an industrial-compatible and highly-rapid electron-beam lithography of ADVANTEST F5112 for the fabrication of a photonic structure. At the University of Paris-SUD, during the returning phase, the fellow has experimentally developed a strategy to integrate the Ge-based photonics device with a SiN waveguide in the University cleanroom. At the same time, several fabrication and characterization runs have been performed with a view to obtain a high-performance Ge-based waveguide integrated structure around the optical wavelength of 1.3 µm.During the three years of the outgoing and returning phase, to advertise the use of GeSi and/or SiNx on ordinary Si wafer for next generation Si-based photonic chip, the fellow has presented the works in 11 international and 1 national conferences in France, Japan, Canada, Spain and China including 3 invited talks.