Research Of Silicon Wavelength Division Multiplexer Based On Asymmetric Couplers

With the rise of next-generation information technologies such as the internet of things and cloud computing,the information age is enriching people's lives,and the demand for communication capacity and communication bandwidth is increasing.As a key component of on-chip multiplexing systems,wavelength division multiplexer plays an important role in improving communication capacity.In this thesis,mode conversion is applied to the siliconbased wavelength division multiplexer using asymmetric couplers,and theoretical analysis,simulation optimization and experimental verification of the designed devices are carried out.Research and innovation have been made to achieve the three goals of a compact structure,excellent performance and large manufacturing tolerance.The main contents are as follows:(1)Silicon-based wavelength division multiplexers based on asymmetric couplers are proposed.Our scheme combines the two dimensions of wavelength and mode.On the one hand,the wavelength signals multiplexed in the bus waveguide are converted into orthogonal modes by asymmetric couplers,which reduces the crosstalk between channels.On the other hand,because mode conversion and wavelength multiplexing occur in the same plane,it is advantageous to integrate with other devices.Theoretically,as long as the asymmetric coupler is added to support the higher order mode conversion,the wavelength division multiplexer can be extended to more channels,realizing the flexibility and scalability of device.(2)Two types of wavelength division multiplexers based on conventional asymmetric directional couplers and tapered asymmetric directional couplers are designed and manufactured.With the advantages of simple structure of the directional coupler,the overall size of the device is less than 7?m ? 120?m.Simulation results show that compared with the conventional asymmetric directional coupler,the tapered asymmetric directional coupler can improve the manufacturing tolerance of the wavelength division multiplexer by introducing the tapered waveguide structure.At the same time,the experimental results show that the wavelength division multiplexer based on tapered asymmetric directional couplers has lower insertion loss(less than 1dB)and smaller crosstalk(less than-23dB).(3)A kind of wavelength division multiplexer based on asymmetric grating-assisted couplers is proposed.The bandwidth can be flexibly adjusted by changing the corrugation width of the grating.The simulation results show that,compared with the asymmetric uniform grating-assisted coupler,the asymmetric unilateral amplitude apodization and bilateral amplitude apodization grating-assisted coupler can suppress the side lobes below-20 dB and-23 dB,respectively.Since the coupling efficiency of the grating-assisted coupler varies monotonously with the coupling length,it reduces the requirement of the coupling length during the manufacturing process and makes the device easier to manufacture and makes the device easier to manufacture.(4)Three types of wavelength division multiplexers based on asymmetric uniform gratingassisted couplers,asymmetric unilateral amplitude apodization and bilateral amplitude apodization grating-assisted couplers are designed and fabricated.The experimental results show that the insertion loss of each wavelength channel is between 0.23 dB and 0.58 dB,and the sidelobe suppress ratio of both unilateral amplitude apodization and bilateral amplitude apodization grating-assisted couplers is larger than 10 dB,which reduces channel crosstalk(about-15dB)and proves the feasibility of wavelength division multiplexer.