Study On Reconfigurable Mode Processing Devices For On-chip Optical Interconnect

The strong demand for high-speed and large-capacity information processing technology has prompted rapid development of on-chip multiplexing technologies.Among many multiplexing technologies,mode division multiplexing technology attracts many researchers'attention because it can integrate various mode processing devices into optical networks at a relatively low cost and large-scale to multiply increase communication capacity.In order to further adapt to the multi-functional,flexible and intelligent high-speed large-capacity optical network applications,it is particularly important to develop new reconfigurable mode processing devices.Based on this significant requirement,this dissertation proposes and demonstrates several key reconfigurable mode processing devices from the perspectives of mode generation,mode multiplexing and mode exchanging,which includes reconfigurable mode converter,reconfigurable mode multiplexer and reconfigurable mode exchange device.As the basic structural unit,optical waveguide is the basis of all integrated optical devices.Therefore,the related theories of optical waveguide are introduced in this dissertation.Then the coupled mode theory as well as phase matching condition are discussed.After that,the theoretical models of micro-ring resonators and multi-mode interference couplers used in optical devices are also studied.In the perspective of mode generation,to solve the problem that most of the proposed mode converters can only achieve fixed mode conversion at present,two kinds of reconfigurable mode converter with selective output of specific modes are proposed and demonstrated in this dissertation.The first one is a reconfigurable device based on cascaded multimode interference couplers to selectively output one or two modes between the fundamental mode and the first-order mode.Simulations was made on this device and the results show that insertion loss of the three working states at output ports is very low,including TE₀ mode output,TE₁ mode output and TE₀+TE₁mode output.The second one is a reconfigurable mode converter based on cascaded micro-ring resonators?MRRs?,which can convert the input TE₀ mode to an arbitrary mode by modulating the MRRs'resonance states.To verify the function of the proposed device,a basic prototype device was fabricated using CMOS process.Static response spectra,dynamic response and high-speed signal eye-diagrams of the fabricated device are measured.The results show that the mode crosstalk is less than-16.9 dB and the wavelength crosstalk is less than-15.2 dB in all working states.The fabricated device can realize the reconfigurable mode conversion of 10 Gbps high-speed signals well.In the perspective of mode multiplexing,a reconfigurable mode multiplexing device with large bandwidth is proposed based on cascaded three-waveguide coupling structure?TWCS?.The simulation results show that the device can realize flexible multiplexing of even symmetric and odd symmetric modes under different phase modulation states.After testing a fabricated basic device,it is found that the crosstalk in the entire C-band is less than-13.7 dB in mode multiplexing.In addition,the fabricated device can achieve a total data throughput of 80 Gbps.In the perspective of mode exchanging,a reconfigurable mode exchange device with compact size is proposed based on MRR to satisfy the demand of multi-mode information processing and network utilization optimizing,which can realize the data exchange function between fundamental mode and any higher-order modes.In order to verify the function,a fundamental mode and a first-order mode exchange device was fabricated.The measured results show that the fabricated device has resonance peaks with extinction ratios larger than 23 dB and mode crosstalk less than-16 dB during mode exchanging process.In addition,the eye diagram measurement yielded clear and open eye diagrams with speed rate of 10 Gbps.At the last of this dissertation,by further extending the three structures of reconfigurable mode converter based on MRRs,reconfigurable mode multiplexer based on TWCS and reconfigurable mode exchange device based on MRRs,three reconfigurable mode multiplexers with advanced functions and one reconfigurable mode exchange device compatible with wavelength division multiplexing network are proposed.The working principle of these devices are also described.