Design And Simulation Of On-chip Communication Devices Structure Based On Integrated Optics

The concept of integrated optics has received much attention since it was proposed,because it is expected to solve the problems of quantum tunneling and heat loss in integrated circuits.Lithium niobate(LN),as a popular common integrated optical material,has many excellent properties,such as large non-linear coefficient,strong electro-optical effect,and wide range of light transmission.With the appearance of the lithium-niobate-on-insulator(LNOI)platform,lithium niobate materials have developed rapidly in integrated optics.At present,there are many integrated photonic devices based on lithium niobate,such as non-linear frequency converter,electro-optical modulator,wavelength division multiplexer and so on.Polarization information is often used as information carrier in optical networks.Polarization Beam Splitter(PBS)is an important component in the polarization diversity system.In this paper,a microring resonator with high quality factor and a PBS with high extinction ratio based on the LNOI platform is proposed from the perspective of integrated optics.The contents are as follows:(1)A near-infrared broadband PBS is designed and numerically Simulated on silicon-on-insulator platform.The PBS is realized by a directional coupler assisted with an Au nanocube array.Its coupling region length is only 1μm.The fundamental transverse electric(TE)mode can be coupled to the output of the upper waveguide by exciting the surface plasmon polariton(SPP),while the fundamental transverse magnetic(TM)mode is output directly from the lower waveguide.The operating bandwidth of the device is 210 nm,and the wavelength range is 1420～1630 nm,covering S band,C band and L band.The simulation shows that the extinction ratio of TE and TM mode is20.31 dB and 14.15 dB,respectively.The result lays a foundation for our device design on the LNOI platform.(2)A microring resonator with high quality factor is designed on the LNOI platform.The anisotropy of lithium niobate material is studied firstly,and some key parameters of thin film lithium niobate waveguide are simulated and discussed.Because lithium niobate is an anisotropic material,its waveguide is also different from the traditional isotropic material.In order to make full use of the characteristics of lithium niobate materials,a series of key parameters such as waveguide bending angle,waveguide thickness,tilt angle,etching depth are compared and analyzed.This ensures that the polarization coupling is effectively reduced and stable mode transmission is guaranteed when the device structure is designed.Then a microring resonator with high quality factor is designed on the LNOI platform,and the structure is simulated and analyzed.(3)A broadband PBS using silicon nanowire assisted waveguide is designed on the LNOI platform.By properly designing the size of the silicon nano-assistant line and the width of the two waveguides,the TE mode satisfies the phase matching condition and is coupled to the downward waveguide.While the TM mode does not produce cross coupling and output directly in the upper waveguide.In the wavelength range of 1500～1600 nm,the polarization splitter has broadband performance of ER>10 dB,and the two modes have ultra-low insertion loss of IL<0.4 dB.