Design And Application Of Lithium Niobate Film Ridge Optical Waveguide

With the increasing speed of Central Processing Unit(CPU),bottlenecks such as large Resistor-Capacitor(RC)delay,small bandwidth and high interconnection power consumption in traditional electrical interconnection technologies have become increasingly prominent.In recent years,integrated optical devices are considered to be a viable alternative due to their advantages of high bandwidth,low transmission power consumption and antielectromagnetic interference.As the core device in the electro-optical interaction process,the electro-optical modulator has its position self-evident.Lithium niobate crystal plays an important role in the fields of optical information processing,electro-optical control,and quantum communication due to its excellent physical and chemical properties and high second-order nonlinear coefficient.In recent years,the emergence of on-chip lithium niobate on insulator(LNOI)technology has brought new changes to lithium niobate-based integrated optics.Lithium niobate thin-film devices have further surpassed the performance limits of traditional bulk crystals,providing more solutions for integrated electro-optic devices.Therefore,research on electro-optical devices based on LNOI is crucial to construct the era of information interconnection.The LNOI ridge optical waveguide is the core device studied in this paper.Thanks to the ridge structure of the device,the light field can be localized in a small size with a high intensity density,thus greatly enhancing the electro-optical interaction capability.With this device,electro-optic control with low half-wave voltage and high response speed can be realized,and the operation is simple.It provides ideas for the subsequent research of lithium niobate optoelectronic integrated devices.Based on the great electro-optical characteristics of LNOI,we have carried out the following work:(1)Tunable single photon linear polarization controller based on LNOI.In the fields of classical and quantum regimes,it is very important to control the polarization state of light quickly and accurately.After detailed analysis of the polarization control mechanism of the periodically poled lithium niobate on insulator(PPLNOI)ridge optical waveguide using the theory of polarization coupled mode,experimentally,the polarization control function of the device for single photons meeting the quasi-phase matching condition(QPM)is demonstrated.According to the electro-optic(EO)effect theory,the linear polarization state of single-photon can be rotated when a transverse electric field is applied to the waveguide.Thanks to the structure of the micron-level ridge waveguide,strong light confinement and large EO coefficient can be realized,thereby significantly reducing the driving voltagelength product(7 V ? cm)while achieving fast-speed modulation(100 MHz).Moreover,quantum entanglement is well maintained during the control of the polarization state,as demonstrated in the time-energy entanglement measurement.In other words,the single-photon after polarization control can be used for subsequent research such as quantum communication and quantum computing.(2)High-speed electro-optical modulator based on LNOI coplanar waveguide(CPW)traveling wave electrode system.In the era of prosperous development of high-speed information technology,the modulation speed of electro-optical modulators has become an important indicator to measure its performance.In order to achieve a higher modulation rate,we have conducted a detailed analysis and exploration of the CPW traveling wave electrode system based on the LNOI ridge waveguide.The modeling and analysis of the optical waveguide and traveling wave electrode structure are realized by COMSOL and HFSS according to the transmission line theory,and the critical parameters of the electro-optic modulation,transition and interface areas are optimized under the guidance of various optoelectronic indicators.Finally,an integrated electro-optical modulation system based on a nano-scale LNOI ridge waveguide with a large 3 d B bandwidth(40GHz)and a low half-wave voltage-length product(4.7 V ? cm)is exhibited.