缺陷态对氮化硅薄膜非线性光学性质的影响

Silicon nitride (SiN) is an important complementary metal–oxide–semiconductor (CMOS)-compatible material. The research on the optical nonlinearity in SiN has great importance for photonic chip-scale integration. Currently, the mechanism of optical nonlinearity due to the defect in SiN film is not clear. The project will systemically study the effects of various defects on second- and third-harmonic generation, and third-order nonlinear refraction in SiN film. we will conduct the research by (1) experimentally modulating and characterizing the type and concentration of the defects in SiN film, measuring the nonlinear response, and finally building the relation between the parameters of defect and the nonlinear optical susceptibility; (2) theoretically simulating the atomic bonding structure of SiN film based on the experimental characterization using molecular dynamics, and calculating the second- and third-order optical susceptibility by time-dependent density-function theory. The aim of the project is to demonstrate the contributions from various defects and the interaction between them to nonlinear response, and to fully understand the mechanism of defects-dependent optical nonlinearity in SiN film. The research will theoretically and technically pave the way for the fabrication of SiN film with optimum optical nonlinearity.

氮化硅是一种重要的CMOS工艺兼容材料，其非线性光学性质研究对于芯片级集成的光子器件应用具有重要意义。目前，对于氮化硅薄膜中与缺陷态相关的非线性光学响应的机理尚不明确。本项目将系统研究氮化硅薄膜中不同缺陷态对二次、三次谐波产生及三阶非线性折射的影响。拟进行（1）实验上，调控并表征氮化硅薄膜中缺陷态的存在形式及含量，测量非线性光学响应，建立不同缺陷态参量与非线性光学极化率的关联；（2）理论上，以实验表征参数为基础，采用分子动力学方法模拟薄膜中的原子成键结构，并利用含时密度泛函理论计算薄膜二阶、三阶非线性光学极化率。本项目旨在阐明氮化硅薄膜中缺陷态对非线性响应的贡献及相互影响，全面揭示氮化硅薄膜中与缺陷态相关的非线性光学响应机制，为制备具有最优非线性光学性质的氮化硅薄膜打下理论和技术基础。

氮化硅薄膜做为CMOS工艺兼容材料，由于其在芯片上可集成光电子学器件的潜在应用，其非线性光学性质研究是近几年来的研究热点。研究非原子配比及结晶结构等缺陷态对氮化硅薄膜非线性光学性质的影响具有重要学术价值和应用意义。实验上，制备了不同组分和结构的氮化硅薄膜，并测量了SiN薄膜的二次谐波产生、三次谐波产生以及三阶非线性折射率和吸收等非线性光学性质。确定了氮化硅薄膜二次谐波产生的最优原子比及对应的二阶非线性极化率。确定了三次谐波产生响应与硅原子含量的正相关性，得到最大三阶非线性极化率。测量了不同氛围下退火的氮化硅薄膜的三阶非线性折射率与吸收系数，获得了了氧气及氩气对氮化硅成分和结构改变对三阶非线性折射率和吸收的影响数据。理论上，尝试了从原子键合角度对非线性光学性质的影响。利用时域有限差分方法计算了硅团簇或颗粒周围局域光场分布，得到了电场增强效应，分析了其对非线性光学性质的影响。本项目所取得的成果，对于理解SiN薄膜非线性响应的机理，并探索制备具有最优成份结构的SiN薄膜用于未来非线性光子学器件具有重要的科学意义。