稀土离子掺杂铌酸锂晶体薄膜波导的研究

Rare earth ion-doped materials are one of the bases for fabrication of optical active devices. Rare earth ion-doped waveguide would be used as active components, such as optical amplifiers and lasers. Near stoichiometric lithium niobate crystal (NSLN) film has many unique advantages, such as, the steep refractive index interface and large refractive index difference between the substrate and the film, the film can be conveniently selective doped. Therefore, lithium niobate film optical waveguide become active multi-function devices. The project aims to employ sputtering technology to grow rare earth ion-doped NSLN crystal films on different low refractive index substrates by using lithium-richer rare earth ion-doped lithium niobate ceramic as target. Moreover, the film surface morphology, film structure, film thickness and fluorescence spectroscopy would be studied. The impact of preparation parameters (such as the gas, the gas pressure and substrate temperature, etc.) on film quality will be studied and the fabrication conditions of fine crystal film waveguides will be found out. Ridge waveguides will be realized by using ultrafast laser micromachining technique. The near-field optical intensity distribution, propagation losses, and fluorescence spectra in ridge waveguides would be tested. This is the foundation for the realization of waveguide amplifier and waveguide laser, and is conducive to integrated waveguide devices.

稀土元素离子掺杂材料是研制光有源器件的基础之一。稀土离子掺杂波导结构可用作光放大器和激光有源元件。近化学计量比铌酸锂晶体（NSLN）薄膜具有许多独特的优点，它可以实现衬底与薄膜间陡峭的折射率界面和大的折射率差, 方便地对薄膜进行选择性的掺杂，使铌酸锂薄膜波导成为光有源多功能器件。本项目旨在研究在不同低折射率衬底材料上，探索用溅射，以富锂稀土元素掺杂的铌酸锂陶瓷为靶材，制备稀土元素离子（如铒）掺杂NSLN晶体薄膜，研究薄膜的表面形貌、薄膜结构，测试薄膜厚度，荧光光谱。研究制备参数（如溅射过程中充入的气体、气体气氛压强及衬底温度等）对成膜质量的影响，找出制备优良晶体薄膜波导的条件。并结合超快激光微加工术制备脊型波导，测试近场光强分布，损耗，荧光光谱等。为实现波导放大器、波导激光奠定基础，有利于波导器件的集成化。

稀土离子掺杂光波导结构是制备光有源器件的基础。飞秒激光微加工可制备通道光波导和易于实现三维结构，是最有前途的技术之一。本项目以铌酸锂陶瓷为靶材，通过改变溅射条件，生长出了LiNbO3晶体薄膜，并形成了薄膜光波导；溅射制备了Er/Yb掺杂ZnO薄膜，研究了衬底材料、衬底温度和溅射时间等参数对成膜的影响，并测试了薄膜的成份、波导性能及荧光特性，结果表明生长出了沿着c轴取向的薄膜，而且室温下测得了1.54μm附近的荧光光谱；搭建了飞秒激光微加工平台，研究了脉冲能量、扫描速度及扫描次数对飞秒激光微加工通道光波导的影响；并进行了稀土铒离子注入掺杂的研究，将铒离子注入到一些材料中，在室温和低温下都测得了1.54μm附近的荧光光谱且退火后的样品荧光强度增大；为探讨薄膜光波导更多的应用，在理论研究上研究了基于薄膜波导的光子晶体平板，得到在铌酸锂薄膜上制备晶格常数为500nm的六角晶格，可获得 250nm的禁带宽度。