Integrated Device Of Multi-channel Electro-optic Modulating And Mode-division Multiplexing Based On Photonic Crystal

With the rapid rise of artificial intelligence,virtual reality,Internet of Things and other applications,mobile Internet,big data,cloud computing and other technologies have developed rapidly,and data usage has skyrocketed.And it is the most urgent to further improve the information transmission capacity and speed.At present,the research on unit devices has become mature,and the use of silicon-based optoelectronic integration technology to integrate multiple functional devices on the same chip to achieve miniaturization and multi-functionality of optoelectronic devices has become a promising research direction.The electro-optic modulator and the mode division multiplexer are the key components of the optical communication system.The integration of the two can reduce the overall device size,reduce the transmission loss,and improve the reliability of the communication system.Therefore,the research of integrated devices for electro-optic modulation and modulus division multiplexing is of great significance to the performance improvement and high integration of optical communication systems.An on-chip integrated device of multi-channel electro-optic modulating and mode-division multiplexing based on photonic crystal is proposed in this paper.The electro-optic modulation module is based on triangular lattice air hole photonic crystal,and adopts the structure of L3 composite cavity coupled with the photonic crystal line defect waveguide side.The mode-division multiplexing module is based on nanowire silicon waveguide and adopts the structure of single mode waveguide and multi mode waveguide coupling.The tapered waveguide structure is introduced into the input and output ports of the photonic crystal plate to reduce the optical transmission loss caused by mode mismatch when the linear defect waveguide is cascaded with the silicon waveguide.Based on the plasma dispersion effect,the L3 composite cavity and PN doped structure are used to modulate two wavelength TE₀ modes.Based on the time-domain coupled mode theory and the transverse coupled mode theory,the TE₀ mode of two wavelengths is converted into TE₁ mode and TE₂ mode by asymmetric directional coupling structure.The Lumerical software based on 3D-Finite Difference Time Domain（3D-FDTD）is used for simulation analysis of the designed device.The results show that when the modulation voltage is 1.05 V,the integrated device can realize on-off modulation,two-mode multiplexing and three-mode multiplexing of TE₀ mode,TE₁ mode and TE₂ mode with the central wavelength of 1552.1 nm and 1556.1 nm.The extinction ratio of the device is up to 24.67 d B,the modulation depth is 0.99,the maximum insertion loss is 0.57 d B,the maximum channel crosstalk value is-34.68 d B,and the minimum modulation rate is 17.54 GHz.The integrated device has excellent performance,small size and easy integration,which has important application value to improve the performance and integration of optical communication system.