Silicon Nanowire Arrayed Waveguide Grating Routers For Optical Interconnects

Future computing and data centers enabled by photonics are currently a hot research topic among the scientific society. The target is to realize enhanced scalability, latency, throughput, and power-efficient optical interconnect framework by all-optical transmission, switching and routing, which can meet global data center traffic growth. Arrayed waveguide grating routers (AWGRs) based on silicon nanowires are recognized as the core optical passive component in future computing and data centers. Silicon nanowire arrayed waveguide grating has the advantages of compact size, high performance and cost effective, and is compatible with CMOS process. When employing as routers by N×N rectangular form, it can simultaneously transporting N1 optical channels at N different frequencies, which greatly improve the bandwidth and scalability. Besides this, AWGRs are easily integrated with other optical components. Therefore, it can meet the demands for future computing and data centers.In recent years, researches on silicon nanowire AWGRs are mainly for dense wavelength division multiplexing optical interconnect, where the channel spacing of the AWGRs is 100GHz or 400GHz. In this thesis, we make a thorough research on the design, fabrication and characterization of silicon nanowire AWGRs for coarse wavelength division multiplexing optical interconnects, where the channel spacing is 625GHz,1250GHz and 2500GHz.The thesis starts from the introduction of arrayed waveguide grating. Basic principle of AWG, including its geometry, operating principle and fundamental characteristics are discussed. Besides this, the development history of silicon nanowire AWG and AWGs based on other material platforms are introduced in this thesis. Furthermore, the performance and characteristic of AWGs from different material platforms are compared and analyzed.Since optical interconnect require all optical components are temperature insensitive, the thesis then analyzes temperature’s influence on the central wavelength of AWG. Meanwhile, researches on athermal AWGs, including SOS and SOI platform, are introduced. Moreover, we propose a new design method using the slab regions as temperature compensators to improve the arrayed waveguide width tolerance as the former method has a very strict waveguide structure requirement.After that, research history of AWGRs is introduced. The domestic and foreign colleagues’ works are also introduced, as they also focus their attention on silicon nanowire AWGRs when our research project is conducted. Specifically, the thesis discusses the basic design method of silicon nanowire AWGRs. A 4×4 AWGR with 1250GHz channel spacing is proposed as a design example, and its design procedure and numerical simulation method are discussed in details. Besides this, substantial marginal output frequency mismatch for silicon nanowire AWGRs with wide free spectral range is analyzed in this thesis.We further introduce the mask design method for silicon nanowire AWGRs. After that, the fabrication processes of silicon nanowire AWGRs are developed. And some fundamental technologies, including lithography technology, deep silicon-etching technology an so on, are discussed in details. In addition, two test systems are set up for edge-coupling and grating-coupling, respectively. The measurements show that our devices have good property, as the on-chip loss of our 4 channels and 8 channels AWGRs with 625GHz,1250GHz and 2500GHz channel spacing varies from 2.5dB to 6dB, while the crosstalk ranges from-12dB to-18dB. The excellent cyclic rotation property for 4×4 1250GHz AWGR is also proposed.In the end, the thesis is summarized and the future research work is planned.