Research On Mode Multiplexer Using Novel Mode Matching Scheme And Its Application

In recent years,mode division multiplexing(MDM)technology has gradually become a hot research direction in silicon-based photonics.Using mode multiplexers to introduce higher-order modes into bus waveguides can greatly improve on-chip communication capacity.For mode-division multiplexing,the channel can be extended to higher-order modes by simply changing the width of the waveguide,and it can be well combined with wavelength-division multiplexing(WDM).This advantage makes the on-chip mode processing device more scalable and flexible.Mode processing devices of various functions such as mode multiplexers,mode switches,mode converters,multimode waveguide bending,and multimode waveguide crossings have been extensively studied.Among them,the micro-ring resonator and the mode multiplexer are the key components of the on-chip wavelength-mode hybrid multiplexing.For wavelength-mode hybrid multiplexing network,a common solution for higher-order modes is introducing cascaded asymmetric directional couplers and utilizing the wavelength selectivity of micro-ring resonators(MRRs)to realize the combination with wavelength division multiplexing.Traditional mode and wavelength division interconnection networks typically use single-mode MRR coupled with asymmetric directional couplers to access wavelength and mode carrier.In such a network structure,it is very inconvenient to directly access the low-order modes in the bus waveguide.Cascaded asymmetric directional couplers are interconnected by adiabatic tapers,thus higher-order modes must be stripped from the bus waveguide before accessing lower-order modes.For building multi-wavelength,multi-mode on-chip networks,a large number of redundant structures will bring additional losses.Therefore,it is critical to find an arbitrary access to mode and wavelength carriers in bus waveguides with a simple and efficient scheme.First,a scheme combining multi-mode MRR and multi-mode waveguide is proposed.By adopting a new mode matching scheme,a bus waveguide of the same width is designed to avoid the introduction of adiabatic tapers and greatly simplify the complexity of the wavelength-mode hybrid network.By controlling the resonance state of each MRR,arbitrary access to the mode and wavelength carriers in the multimode bus waveguide can be achieved.Devices that can access any wavelength in the first three-order modes(TE₀,TE₁,and TE₂)in the bus waveguide are designed and fabricated,The extinction ratios of the devices are all larger than 21.0 dB.Mode crosstalk and wavelength crosstalk are less than-12.8 dB and-19.0 dB,respectively.The device has excellent performance,novel structure and good scalability.In addition,based on the novel mode multiplexing structure,a four-port multi-mode optical router for on-chip optical interconnection network is proposed.The router consists of four multi-mode micro-ring resonators.Any wavelength and mode carrier can be routed from the corresponding input and output ports.Compared with the traditional routing network introduced with MDM,the scheme of"multi-mode waveguide?demultiplexing?multiple single-mode waveguide interconnection?multiplexing?multi-mode waveguide"is avoided.The routing network is completely constructed with multi-mode waveguides,and the discrete structure of the device is studied by means of simulation.A cross-waveguide micro-ring resonator suitable for multimode routing network is constructed by using the modified Euler curve.The multimode waveguide cross is optimized by the reverse design method,and good simulation results are obtained.