【作者】 马峥；

【导师】 张德龙； 姜城；

【作者基本信息】 天津大学 ， 工程（专业学位）， 2022， 硕士

【摘要】 条形光波导是集成光学器件和系统的基本单元,被用于研发各种性能优异的电光调制器、光滤波器等光子器件。然而,光波导材料的光折变效应严重影响导波器件的性能。因此,为实现性能更为优异的导波器件,开展条形光波导光折变性质测量的研究工作具有十分重要的意义。本文制备了钛扩散铁掺杂铌酸锂平面和条形光折变光波导,并对其导波特性进行了实验表征,搭建了光折变波导光栅写入和读出实验系统,并成功实现了所制作的条形光波导光折变性质的准确测量。所完成的测量系统为开展条形光波导光折变效应的研究工作奠定了基础。本论文的主要研究内容和结果包括:1.采用磁控溅射技术和高温钛扩散方法在X切0.05 wt%铁掺杂铌酸锂晶体表面制作出了平面波导,并对其进行了光学表征。测量了在波长为1311和1553nm晶体表面寻常光、异常光折射率以及632.8 nm波长下平面波导中传输的TE、TM导模的有效折射率。基于铌酸锂晶体的Sellmeier方程确定了晶体中氧化锂含量为47.9±0.1 mol%,采用IWKB方法获得了平面波导的高斯型折射率深度分布。2.采用光刻和钛扩散相结合方法制作出了初始钛条宽度为8μm的X切Y传钛扩散铁掺杂铌酸锂条形光波导,并对其导波特性进行了实验表征。结果表明,在1.5μm波长,所制作的条形波导在TE和TM偏振下支持单模传输,其传输损耗分别为3.2±0.1 d B/cm和1.4±0.1 d B/cm。所测得的近场模式显示:TE和TM模场在波导的宽度方向遵从高斯分布,在深度方向遵从厄米-高斯分布,1/e模场尺寸分别为35.90±0.01μm²和47.02±0.01μm²。3.设计、搭建了基于双光束干涉的光折变波导光栅写入以及基于光纤-光波导端面耦合技术的光栅衍射效率测量的实验系统。利用该系统在所制作的条形波导内成功写入了6 mm长的布拉格光折变光栅。测量了1.5μm波段所写入波导光栅的透射谱,发现在1546、1551、1556 nm处可以实现有效光栅衍射滤波,衍射效率达77.8%。根据测得的衍射效率进一步计算得到了波导光栅的折射率变化幅度为（1.14±0.01）×10^-4,与理论值一致,表明利用本实验系统可以实现对条形波导光折变效应的准确测量。此外,还尝试对所写入的光折变波导光栅进行了热固定处理,衍射效率测量结果显示:热固定光栅的滤波效率可达68.6%。更多还原

【Abstract】 Strip optical waveguide is the basic unit of integrated optical devices and systems.It is used to develop various photonic devices with excellent performance,such as electro-optic modulator,optical filter and so on.However,the photorefractive effect of optical waveguide materials seriously affects the performance of guided wave devices.Therefore,in order to achieve better guided wave devices,it is of great significance to carry out the research on the measurement of photorefractive properties of strip optical waveguide.In this paper,titanium diffused iron doped lithium niobate planar and strip photorefractive optical waveguides are prepared,and their guided wave characteristics are experimentally characterized.The photorefractive waveguide grating writing and reading experimental system is established,and the accurate measurement of the photorefractive properties of the fabricated strip optical waveguides is successfully realized.The completed measurement system lays a foundation for the research of photorefractive effect of strip optical waveguide.The main research contents and results of this paper include:Firstly,planar waveguides were fabricated on the surface of X-cut 0.05wt%iron doped lithium niobate crystal by magnetron sputtering and high temperature titanium diffusion method.The refractive indices of ordinary light and extraordinary light on the crystal surface with wavelengths of 1311 and 1553 nm and the effective refractive indices of TE and TM guided modes transmitted in planar waveguides at 632.8 nm were measured.Based on the Sellmeier equation of lithium niobate crystal,the content of lithium oxide in the crystal is determined to be 47.9±0.1 mol%.The Gaussian refractive index depth distribution of planar waveguide is obtained by IWKB method.Secondly,the X-cut Y-transfer Ti diffused iron doped lithium niobate strip optical waveguide with an initial width of 8μm was fabricated by the combination of lithography and titanium diffusion,and its guided wave characteristics were characterized experimentally.The results show that at 1.5μm wavelength,the fabricated strip waveguide supports single-mode transmission under TE and TM polarization,and its transmission loss is 3.2±0.1 d B/cm and 1.4±0.1 d B/cm respectively.The measured near-field modes show that TE and TM mode fields follow Gaussian distribution in the width direction of the waveguide and Hermite Gaussian distribution in the depth direction.The dimensions of 1/e mode fields are35.90±0.01μm²and 47.02±0.01μm²respectively.Thirdly,the experimental system of photorefractive waveguide grating writing based on double beam interference and grating diffraction efficiency measurement based on fiber optical waveguide end coupling technology are designed and built.Using this system,a 6 mm long Bragg photorefractive grating is successfully written in the fabricated strip waveguide.The transmission spectrum of the waveguide grating written in 1.5μm band is measured.It is found that effective grating diffraction filtering can be realized at 1546,1551 and 1556 nm,and the diffraction efficiency is77.8%.According to the measured diffraction efficiency,the variation amplitude of the refractive index of the waveguide grating is（1.14±0.01）×10^-4,which is consistent with the theoretical value,shows that the experimental system can accurately measure the photorefractive effect of strip waveguide.In addition,the photorefractive waveguide grating is also tried to be thermally fixed.The diffraction efficiency measurement results show that the filtering efficiency of the thermally fixed grating can reach 68.6%.更多还原