Silicon-based Passive Devices For On-chip Optical Interconnection

With the growth of voice service and the continuous emergence of new service in data and image fields,especially the rapid development of FTTH and IP network technology,the information capacity and processing speed of current communication system grows explosively.However,the electronic interconnection based on metal conduction is facing the severe heat dissipation and the insurmountable electronic bottleneck.It has been more and more difficult for the electronic interconnection to meet the requirements of high speed and broad bandwidth in the information storage,information transmission and information processing.Optical interconnection,in place of the electrical interconnection on the chip,is a powerful means to realize the high-density and high-rate data transmission and break the aforementioned bottlenecks with the photon as the information carrier and the waveguide as the transmission medium.The development and integration of planar optical devices is the footstone of on-chip optical interconnection.Silicon photonics,based on the silicon material,is considered as the most promising optical interconnection platform thanks to the promotion of microelectronics industry,the deepening of research on silicon properties and the gradual maturity of silicon-compatible technology.In this thesis,we mainly focus on the wavelength converter and wavelength division multiplexer/demultiplexer,which are the key passive devices for the silicon-based on-chip optical interconnection.Firstly,we introduce the classification of silicon-based waveguides and the main numerical simulation methods.Then,the finite-difference time-domain method is used to analyze the mode distribution and linear transmission properties of strip-type waveguide and slot-type waveguide.Next,several nonlinear effects in silicon waveguide are introduced.Subsequently,we introduce the fabrication and test of silicon nanowire waveguide,including the key equipment,the main process,the test method and the coupling means.On the basis of the nanowire waveguide,the FWM-based silicon wavelength converter and the silicon wavelength division multiplexer/demultiplexer are studied.Wavelength converter avoids the limitation of wavelength continuity,increases the data bandwidth of on-chip interconnection,and improves the network efficiency.In order to improve the conversion efficiency of the silicon wavelength converter,we attempt from the following two aspects:enhancing the nonlinear coefficient and regulating the phase mismatch.For the former,we design a high nonlinear horizontal slot waveguide,whose nonlinear coefficient achieves 4100 W-1m-1,20 times that of the strip waveguide with the same size.For the latter,two kinds of quasi-phase matching schemes,phase-mismatch switching(PMS)and phase-mismatch compensation(PMC),are proposed to adjust the phase mismatch and improve the conversion efficiency at the target wavelength.The results show that the conversion efficiency is improved by 11.3 dB and 18.3 dB respectively in PMS scheme and PMC scheme.Subsequently,the conversion performances of PMS and PMC schemes under the condition of double pump are analyzed.In the situation of low pump power,it is more likely to obtain higher efficiency in the non-degenerate FWM process than in the degenerate FWM.In addition,we propose an enhanced quasi phase matching scheme(EPMC)to further enhance the energy transfer intensity and improve the conversion performance.The high conversion efficiency of-11.3 dB and 3-dB bandwidth of 516 nm have been achieved.Wavelength division multiplexer/demultiplexer is the core of on-chip interconnection.It plays a very important role in the enhancement of communication bandwidth by combining and dividing multi waves.The common optical design method set up barriers for the designers to obtain the planar optical devices with higher integration and better performance.The metamaterial structure nanoengineers the local permittivity at the subwavelength scale,providing a new way of efficient photon control.In order to eliminate the influence of lag effect on etching depth,we propose a lag-insensitive photonic-crystal-like metamaterial structure with the partial-filling pixels to ensure the distribution isolation and dimensional uniformity of the etching patterns.Then we utilize Direct-binary search algorithm,a reverse design method,to design and fabricate a compact wavelength demultiplexer suitable for CWDM system.The demultiplexer exhibits low loss,low crosstalk,broad bandwidth and large temperature tolerance.Compared with the demultiplexers reported,the channel density of our device is imporved by two orders of magnitude.