Study On Microring Resonator Of Single Crystal Lithium Niobite Films

With the advent of the global information age,optical communication network technology is developing rapidly in the direction of high integration,high rate,and large capacity.In recent years,in order to improve the adaptability and flexibility of optical network,integrated optical devices with different structures have emerged endlessly.Due to the advantages of modularization,miniaturization,and integration,integrated optical devices have become the focus of future development of optical communication technology.The microring resonator is a particularly important basic optical component.Due to its small size,compact structure,high integration,stable performance,and good wavelength selectivity,it can be used to form complex devices with various performances,such as lasers,optical filters,optical modulators,optical switches,sensors,optical delay lines.This thesis takes single crystal lithium niobate thin film microring resonator as the research object,and conducts systematic research on basic theory,simulation modeling,preparation process and so on.In this paper,lithium niobate?LiNbO₃,LN?is used as the core material of the optical waveguide.Its comprehensive performance is excellent,with wide light transmission range,large nonlinear coefficient,strong piezoelectric effect and pyroelectric effect.Lithium niobite on insulator?LNOI?as the basic structure,the microring resonator was designed,fabricated and tested.The main research contents and research results of this article are as follows:1.Research on simulation modeling of microring resonatorAccording to the theory of optical waveguide and the working principle of the microring resonator,COMSOL finite element simulation software was used to model and simulate the straight waveguide and microring waveguide successively,and the parameters such as the waveguide end face size,coupling spacing,coupling length and curvature radius were designed and optimized.Finally,the mask layout was completed.2.Research on etching process of microring resonatorLNOI was selected as the basic structure,and the waveguides were etched on the lithium niobate films.In the preparation of optical waveguide,a metal chromium?Cr?film was prepared as a mask by magnetron sputtering,and the two types of etching,argon ion?Ar⁺?etching and reactive ion etching?RIE?,were mainly studied technology.Through comparative analysis,it is found that although the Ar⁺physical etching rate can reach the maximum etching rate of 95 nm/min under the adjustment of equipment parameters,it is difficult to obtain smooth and steep waveguide side walls,and the etching selectivity ratio with Cr as mask is 1:1,poor selectivity means that it is difficult to achieve deep etching of lithium niobite.The etching rate obtained by RIE is relatively flat,which is 7 nm/min.The etching selectivity ratio with hard mask of Cr can reach more than 6:1,and the smooth and straight side wall morphology can be obtained.Finally,a ridge waveguide with a width of 4?m and a height of 350 nm on the lithium niobate thin film of 400 nm was fabricated by RIE,and its transmission loss was about5.3 dB/cm through optical testing.The feasibility of passing light is verified,which lays the foundation for the subsequent preparation of microring resonators.In the end,combined with the layout of the design,a microring resonator was successfully fabricated on a single crystal lithium niobate thin film with a thickness of 400 nm using the same RIE process as the optical waveguide.3.Research on optical testing of microring resonatorsSequential optical waveguides and microring resonators were tested optically.According to the test data,the transmission loss of the straight waveguide is about 2.6dB/cm,the coupling loss is about 29 dB,the transmission loss of the straight waveguide is low;the Q value of the microring resonator is 12517.58,the modulation depth is23.36 dB.The Q value of the microring resonator is high,the modulation depth is large,and the performance is excellent.Finally,by comparing and analyzing the test data with the simulation results,it is judged that the simulation design basically conforms to the actual situation of the device.