Community Research and Development Information Service - CORDIS

Periodic Report Summary 1 - MIDEX (Mid refractive Index contrast Si photonics platform for telecommunication applications)

1. Summary of the project objectives
In this report we summarize the research activity performed by Dr. Papichaya Chaisakul during the outgoing phase of the Marie-Curie IOF at the Department of Materials Engineering, the University of Tokyo. The fellow proposed to develop a new Si Photonics platform based on mid-refractive index contrast optics (MiDex) to overcome the incompatibilities of current HiDex Si Photonics for the future dense WDM system.
The main objectives as in the Part-B of the proposal are the following:
i. Well understanding of SiN/SiOxNy optical properties at optimized conditions for Dense WDM system.
ii. Development of dense and optimized WDM SiOxNy optical circuitry.
iii. Development of integration between GeSi optoelectronic devices and SiOxNy passive optical circuitry on bulk silicon wafer.
iv. Development and demonstration of high speed data communication from MiDex platform.

These 4 objectives have to be performed in 36 months. In the proposal's timeline, we planned to perform the first 3 objectives during the outgoing phase (24 months). According to this, we have undergone the first 3 objectives and will performed the remaining parts during the returning phase at the University of Paris-Sud (France).

2. Description of the work performed since the beginning of the project
During the first months of the project, according to the objective i, 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 have been verified to be promising for the realization of high-performance photonic components. Subsequently according to the objective ii, 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. With respect to the objective iii, the fellow finished the design of an optical coupling integration between Ge-based device and SiNx waveguide. The fellow 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 and its limitation of fabricating a photonic structure.

3. Description of the achieved results
With the research activity performed during the outgoing phase, the first three work packages have been performed at the University of Tokyo according to the work plan. The fellow, with master students at the University of Tokyo, determined the optical propagation loss of SiNx waveguide deposited at room temperature. The fellow also fabricated and tested AWG based on SiNx and reported the obtained optical characterization results. From 3D FDTD results, the fellow have identified a coupling strategy that would allow a low-loss Ge-SiNx integration over a wide spectral range with a good fabrication tolerance for mass production in CMOS facilities.

4. Expected final results and their potential impact
After the returning phase, the fellow expects to have developed a SiNx-integrated Ge-based optical circuitry at the University of Paris-Sud. From the obtained know-how and experience at the University of Tokyo, the fellow is confident to realize such final prototype within the returning year. Virtually all of the previous and present Si Photonics efforts in US, EU, and Asia are based on HiDex platform of SOI waveguide. The aimed demonstration of high speed data transmission using MiDex platform built side by side with Ge active components on ordinary Si wafer is definitely a major breakthrough.

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