【作者】 宋强；

【导师】 卢霏；

【作者基本信息】 山东大学 ， 光学工程， 2008， 硕士

【摘要】 集成光学的概念是1969年由美国贝尔实验室提出，它的提出大大促进了的光通信的发展，同时也是今后全光网络传输以及全光计算的基础。集成光学是以光波导现象为基础的光子和电子系统，系统的连接通过光波导和光纤，系统的基本元件是光波导器件。利用光在折射率不同的两种物质的界面上会发生全反射的原理，光波导将光波限制在微米量级的薄膜内传输。集成光学的研究内容异常丰富，但其根本的基础是在薄膜中的传输，对光讯号的所有处理，都必须以光在薄膜中能够传导为前提，因此光波导在集成光学中起着重要作用。离子注入法作为制作光波导的一种重要方法，相对于其他制作波导的方法有以下优点：可以改变材料的折射率，而基本不改变材料的光电特性，对晶体波导层结构影响小，可以在较低温度进行，对注入剂量和深度可以精确控制等。其中离子注入分轻离子注入以及新兴的低剂量重离子注入两种。重离子注入的优点有：离子剂量相对较低，比轻离子注入低2到3个数量级。这就使注入时间大大缩短，从而降低制作成本。重离子注入形成的损伤层在晶体表面下1um到1．5um之间，比较容易形成单模波导。铌酸锂（LiNbO₃）晶体具有大的电光、声光及非线性光学系数，材料的化学性能稳定，晶体生长成本低且易生长出大尺寸的单晶等优点而广泛用于制备各种光波导器件，成为集成光学最常用的晶体材料，在单模光纤通信系统、信号处理、传感器等领域有重要的应用，同单晶硅一样是一种不可多得的人工晶体。铌酸锂晶体之所以有如此丰富多彩的性质和应用前景，还与其众多的掺杂元素密不可分。纯铌酸锂晶体给我提供了一个良好的平台，各种各样的掺杂才使得晶体变得如此重要。其中高掺镁（莫尔分数超过4．6％时）的铌酸锂（MgO：LiNbO₃）晶体的抗光折变能力可以提高两个数量级以上。掺镁铌酸锂的高抗光损伤能力适应了波导器件在调制器、倍频器、波导激光振荡等高功率密度的应用要求，因此制作MgO：LiNbO₃离子注入光波导和进一步研究其光学及结构特征对于拓宽波导器件的应用领域具有重要意义。我们主要选择5％mol掺镁铌酸锂（MgO：LiNbO₃）作为试验材料。传统的铌酸锂波导制作工艺Ti扩散法和质子交换法用来制作掺镁铌酸锂光波导有一定的局限性。如使用Ti扩散法制作掺镁铌酸锂光波导，扩散系数减小，扩散区的抗光折变性能有所下降；使用质子交换法，扩散速度减慢。并且Ti扩散法和质子交换法制作的波导损耗较大，对实际应用有一定的影响。由于离子注入的自身优点，离子注入法有望成为制作低损耗掺镁铌酸锂光波导的有效方法。我们对低剂量O²⁺注入Z切的MgO：LiNbO₃晶片的性质做了一些研究。首先制作了平面MgO：LiNbO₃光波导，注入离子能量从1．5MeV到4．5MeV，注入剂量从4×10¹⁴到12×10¹⁴ions／cm²。分别在633nm和1539nm波长TM偏振下形成了异常光折射率增加型的单模波导。观察并测量了波导损耗和折射率分布随退火条件的变化，并得到了寻常光折射率和异常光折射率随退火温度升高而变化的规律。经过230℃，30分钟退火，波导的传输损耗下降到0．9dB-2．0dB。介绍了制作MgO：LiNbO₃条形波导的研究，分别使用单能量和多能量注入氧离子注入有条形图案金属掩膜的样品，形成条形波导。单能量注入条件为注入能量1．5MeV和3．5MeV注入剂量为6×10¹⁴ions／cm²；多能量注入的注入能量为3．0MeV+3．6MeV+4．5MeV，总注入剂量为8．8×10¹⁴ions／cm²；。其中多能量注入和单能量3．5MeV注入形成的条形波导在光纤通讯波段1550nm波长TM偏振下形成了低损耗的单模波导，其中多能量注入形成的条形波导测得的损耗范围主要在0．38-0．45dB／cm之间，符合实际应用对光波导损耗的要求（小于1dB／cm）。本文系统的研究了氧离子注入MgO：LiNbO₃晶体制备平面波导和条形波导。研究了不同注入条件下的晶体光学性质的变化，以及不同退火条件处理对波导折射率、导波模式和波导损耗的影响，为制备低损耗MgO：LiNbO₃波导器件提供了丰富的试验依据。更多还原

【Abstract】 Since the notion of integrated optics has been proposed by Bell Lab in 1960s, it greatly promote the development of optical communication, it is also the basic of full optical communication and calculation. Integrated optics is a combined system of photon and electron which based on the waveguide phenomena, connected by optical fiber and waveguide. The elemental components are waveguide devices. Using the theory that light will totally reflect in the interface of material with different refractive index, light wave propagation is confined in micron dimension film. The contents of integrated optics are extremely abundant, but the very foundation is light transmission in films. All the processing of light signals must depend on light wave propagate in films. Thus, waveguide play a crucial role in integrated optics. Therefore, people apply various technologies to fabricate waveguide.Ion implantation has following merits comparing to other methods such as diffusion and exchange: it can change the refractive index of materials without changing the materials’ optoelectronic properties and has little damage on crystal structure of waveguide layer; it can process in relatively low temperature; and we can precisely control the dose and depth of implantation.Ion implantation includes two methods, one is light ion implantation and the other one is a new method called low dose heavy ion implantation. Heavy ion implantation has following advantages: the dose of ions is very low and two or three magnitude orders lower than light ion implantation which can reduce implantation time considerably and lower the fabrication cost consequently; the damage layer of heavy ion implantation is beneath the crystal surface about 1um to 1.5um which can easily form single mode waveguide.Lithium Niobate （LN） is widely and most frequently used for preparation of variety of waveguide devices due to its large optoelectronic, opt acoustic and nonlinear coefficients and stable chemical capacities as well as low cost to grow big single crystals. It has important applications in the fields of single mode fiber communication systems, signal processing and sensors etc. This artificial crystal is as valuable as silicon crystal.Lithium Niobate has such versatile properties and promising applications also closely relate to its numerous doping elements. Pure lithium Niobate provide us a good platform, various dopant make this crystal so important. Of which high doped magnesium （over 4.6%mol）, photorefractive resistance ability improve in two magnitude orders. MgO: LiNbO₃’s high resistance to optical damage meets to the application requirement of high power density devices such as modulator, frequent doublers and waveguide laser resonator. To fabricate and further investigate the optical and structure characters of MgO: LiNbO₃ ion implantation waveguide has an important value in broaden the application areas of waveguide devices. Therefore, we mainly use magnesium doped lithium niobate （MgO: LiNbO₃） as experiment materials.Conventional waveguide preparation methods for LN such as Ti diffusion and proton exchange meet several difficulties when apply to MgO: LiNbO₃. Using Ti diffusion method, both the diffusion coefficient and photorefractive resistant ability will decrease. Using proton exchange method, the diffusion speed will slow down. Moreover, waveguide made by these two methods has a comparably large propagation loss. Due to the advantage of ion implantation method, it might become an effective approach to make low loss MgO: LiNbO₃ waveguide.We did research on Z-cut MgO: LiNbO₃ samples implanted by low dose O²⁺ ions. Firstly, we made MgO: LiNbO₃ planar waveguide with implantation energy from 1.5MeV to 4.5MeV and implantation dose from 4×10¹⁴ to 12×10¹⁴ions/cm². Single mode waveguide was formed by increased extraordinary refractive index at TM polarization of wavelength of 633nm and 1539nm respectively. The change of waveguide loss and refractive index profile followed by different annealing treatments were observed and measured. After annealing at 230℃and 30miniutes, the propagation loss of the waveguide was down to 0.9dB-2.0dB.Research on fabrication of MgO: LiNbO₃ channel waveguide was introduced. Both single energy and multiple energy ions were implanted into samples with stripe patterned metal mask to make channel waveguide. The implantation parameter of single energy is 1.5MeV and 3.5MeV with same implantation energy 6×10¹⁴ions/cm², while 3.0MeV+3.6MeV+4.5MeV and totally implantation dose of 8.8×10¹⁴ions/cm² The samples of multiply energy implantation and 3.5MeV implantation formed low loss single mode waveguide with TM polarization at wavelength of 1550nm which is the fiber communication wave band. For multiple energy implantations, the measured propagations lie mainly between 0.38-0.45dB/cm, the value matches the requirement for practical application （smaller than 1dB/cm）.This thesis systematically researched on fabrication of MgO: LiNbO₃ channel and planar waveguide using oxygen ion implantation. The change of sample’s optical properties formed by different implantation parameters was analyzed. The effects of different annealing parameters for refractive index and waveguide loss were discussed. All the data and analysis provide rich experimental basis for fabricating low loss MgO: LiNbO₃ waveguide devices.更多还原