Z切LiNbO3晶体中退火质子交换光波导特性的研究

系统地研究Ｚ切ＬｉＮｂＯ３晶体中质子交换波导和退火质子交换波导的特性,得到了质子交换过程中的扩散常数和激活能。发现了质子交换波导的折射率呈线性阶跃型的折射率分布。通过连续退火,波导的折射率分布由线性阶跃型向高斯型过渡。退火可分为两个阶段,波导深度的增加在第一阶段随退火时间成指数关系,第二阶段与退火时间的平方根成线性关系。     

气相质子交换LiTaO3光波导及其特性

本文利用苯甲酸气相质子交换技术制备了LiTaO3光波导，测量了Z-切LiTaO3光波导的参数（交换深度d和表面折射率增量△nc）和X-切LiTaO3光波导的红外吸收谱，给出了光波导层的折射率分布，并与液相质子交换热退火光波导的结果进行了比较。实验结果表明：非寻常折射率分布与热退火液相质子交换方法制备的LiTaO3光波导基本相近，但表面非寻常折射率增量（△nc）更大，其折射率分布更接近于高斯型。     

质子交换和热退火LiTaO3光波导特性

本文报道了质子交换ＬｉＴａＯ３光波导层的晶格常数变化、质子浓度分布和折射率分布以及红外吸收谱等的测量方法和结果，并与热退火后的测量结果进行了比较。实验结果表明：热退火处理的光波导其非寻常折射率的增高不依赖于质子浓度。     

掺镁铌酸锂质子交换光波导光学性能的研究

本文用质子交换反应在5mol％MgO:LiNbO_3晶体中引起了e光折射率的增加,晶体中MgO的存在并不影响LiNbO_3质子交换光波导阶跃型折射率分布的特点。用常规的质子交换法制备的MgO:LiNb·O_3波导存在着损耗大和有效折射率不稳定的缺点,经过退火处理后,这些缺点可明显地得到改善。     

MgO:LiNbO_3与LiNbO_3质子交换光波导光学及结构特征的比较

利用退火的质子交换法在MgO :LiNbO3和LiNbO3两种材料上制作了光波导 ,得到了质子交换的扩散特性以及光波导折射率分布的退火规律 .通过x射线衍射和OH- 红外吸收谱方法研究了MgO :LiNbO3和LiNbO3质子交换光波导的结构特征及其与退火参数的关系 ,对MgO :LiNbO3和LiNbO3光波导光学和结构特征的结果进行了分析和比较     

MgO:LiNb0.3与LiNb0.3质子交换光波导光学及结构特征的比较

利用退火的质子交换法在MgO:LiNbO.3和LiNbO.3两种材料上制作了光波导，得到了质子交换的扩散特性以及光波导折射率分布的退火规律．通过x射线衍射和OH-红外吸收谱方法研究了 MgO:LiNbO.3和LiNbO.3质子交换光波导的结构特征及其与退火参数的关系，对MgO :LiNbO.3和LiNbO.3光波导光学和结构特征的结果进行了分析和比较． 关键词： 退火质子交换光波导 晶格结构 x射线衍射 红外吸收     

X切H:LiNbO3光波导的工艺仿真研究

对于X切H:LiNbO₃光波导,在532 nm和1310 nm波长下,用棱镜耦合器进行了工艺仿真研究.对于在150℃,180℃和200℃用苯甲酸质子交换的光波导,分别求得交换厚度与交换时间的关系曲线,在此基础上给出质子交换的扩散系数与交换温度的关系曲线.对于在180℃质子交换并在350℃退火的光波导,给出以交换时间(交换厚度）为参变量的表面折射率增量、有效厚度与退火时间的关系曲线.研究结果可供低损耗α相单模波导的设计和制备做参考.     

统计优化迭代法测量质子交换波导折射率分布

提出了一种用于拟合测量渐变波导的折射率分布的新的理论处理。该方法把统计优化手段导入循环迭代法 ,可适用于费米函数这一类曲线变化范围大、且有多个自变量的函数。实验上用焦磷酸质子交换制备了LiNbO3波导样品 ,用该方法对退火后的折射率分布作了测量拟合 ,折射率拟合值与实验值的均方差为± 8.2× 10 - 4。     

X切H∶LiNbO_3光波导的工艺仿真研究

对于X切H∶LiNbO3光波导,在532nm和1310nm波长下,用棱镜耦合器进行了工艺仿真研究.对于在150℃,180℃和200℃用苯甲酸质子交换的光波导,分别求得交换厚度与交换时间的关系曲线,在此基础上给出质子交换的扩散系数与交换温度的关系曲线.对于在180℃质子交换并在350℃退火的光波导,给出以交换时间(交换厚度)为参变量的表面折射率增量、有效厚度与退火时间的关系曲线.研究结果可供低损耗α相单模波导的设计和制备做参考.     

质子交换铌酸锂多模干涉光功分器的研制

采用退火质子交换工艺在铌酸锂衬底上实现了渐变边界MMI光功分器。测量表明该器件有较好的光均分功能。利用红外光谱技术分析了利用纯苯甲酸质子交换源的退火质子交换波导的红外吸收光谱特性证明通过当地选择质子交换温度、时间和退火的温度与时间，可以实现低损耗质子交换光波导的制作。     

Styrene acrylonitrile (SAN) based polymeric waveguides

In the present study styrene acrylonitrile based polymeric waveguides have been optimized with the help of aging (variation of baking time keeping the temperature constant), annealing (variation of baking temperature keeping the time constant), concentration and thickness (physical). Propagation losses are lowest at an annealing temperature of 100°C and aging time of 8 h. The values of effective refractive index of the waveguides change inconsistently between 1.566 and 1.569 and between 1.5660 and 1.5667 for aging and annealing effect, respectively. However, by increasing the physical thickness of the film, the value of refractive index was decreased. By increasing the concentration of the solution, the refractive index of the waveguides was increased. The birefringence in the present observation is of the order of 10⁻⁴. Polarization selective properties were also observed in the present study for certain range of concentration.     

Cu2+离子注入的石英光波导的特性研究

利用Cu2+离子注入的方式在熔融石英和石英晶体上分别制备了平面光波导结构.通过棱镜耦合实验测试了两种光波导的导模特性,结果表明:在同样的注入条件下熔融石英上形成了增加型的光波导结构,而石英晶体上形成了位垒型的光波导结构.研究了退火温度对两种光波导导模折射率的影响,熔融石英光波导中导模的折射率随着退火温度的升高而降低,而石英晶体光波导中导模的折射率随着退火温度的升高先增加后降低.为了进一步分析离子注入两种材料形成光波导的微观机理,利用SRIM模拟了Cu2+离子注入两种材料的电子能量损失和核能量损失,并且模拟了两种光波导结构的折射率分布.模拟结果表明:熔融石英光波导的主要形成原因是离子注入表面的折射率大于其体材料的折射率,而石英晶体光波导的主要形成原因是离子射程末端的折射率小于其体材料的折射率.因此,在熔融石英光波导的形成中电子能量损失起主要作用,而在石英晶体光波导的形成中核能量损失起主要作用.     

掩埋型离子交换玻璃光波导的变分分析

用变分法对离子交换法制备的掺铒光波导的传播特性进行了分析,推导出了适用于掩埋型离子交换玻璃沟道光波导中场分布传播常量的变分表达式,构建了场分布的厄米-高斯型试探解,在两种不同实验条件下,采用变分法确定了试探解中的待定参量,获得光波导中的场分布,利用传播常量的变分公式和已确定的场分布计算得到了传播常量和有效折射率。计算数据表明:导波区域的有效折射率稍稍地大于限制层的折射率,说明离子交换法制备的波导器件是弱波导;高的辅助退火电场强度和适当的退火时间下,所制备的光波导可以支持更多光模式的传输。该方法计算过程简洁、快速,计算结果与实验结果吻合。     

Reduction of insertion loss after annealing of silicon oxynitride optical waveguides

The insertion losses of silicon oxynitride (SiON) waveguides have been measured in the 1550 nm wavelength region. The waveguide structure consisted of a 2.0μm SiON waveguide core with a refractive index of 1.50, a 0.5μm SiO₂ upper cladding and a 5.0μm SiO₂ lower cladding with a refractive index of 1.45. It was found that the wavelength-dependent insertion losses of the waveguide were greatly reduced by annealing, and the loss was decreased more than 5.7 dB/cm at 1550 nm after annealing at optimum conditions. The former was attributed to the reduction of the absorption caused by N-H and Si-H vibration modes, and the latter was due to the improvement of the interface roughness and homogeneity in the waveguides after annealing.     

Dependences of the refractive indices on the proton concentration in H:LiNbO3 waveguides

Proton-exchanged optical waveguides in lithium niobate crystals exhibit a rich variety of structures and phases. It is established that seven H_xLi_1−x NbO₃ crystalline phases with a lithium niobate structure may form under various conditions of proton exchange and post-exchange annealing. A method is proposed to determine the proton concentration in the various phases identified. Relationships are established between the structural parameters, the proton concentration, and the ordinary and extraordinary refractive indices of various H_xLi_1−x NbO₃ crystalline phases. The results can explain various optical phenomena observed in proton-exchanged waveguides and permit prediction of the characteristics of light-guide structures. Zh. Tekh. Fiz. 69, 47–57 (March 1999)     

Optical property modification of PMMA by ion-beam implantation

Polymeric waveguides were fabricated by proton implantation on poly(methyl methacrylate) (PMMA). Depth profiles of the refractive indices of modified regions were obtained and were found to be in good agreement with the stopping power curve of protons in PMMA. It means that the waveguides are formed at the depths where the stopping power is the maximum value. Light losses for 635 nm wavelength were measured using planar waveguides to verify if the transmittance is enough for the application of the technique to optical devices.     

Photoconductivity and photovoltaic behaviour of LiNbO3 and LiNbO3 waveguides at high optical intensities

The photoconductivity and photovoltaic currents of pure LiNbO₃ and proton exchanged waveguides in LiNbO₃ have been measured as a function of the optical intensity up to about several kW/cm² by the use of surface electrodes. For pure LiNbO₃ the observed dependences are a simple extrapolation of the well known low intensity behaviour. The photoconductivity of proton exchanged waveguides is considerably increased compared with pure LiNbO₃ and the curves are strongly nonlinear in the high intensity region. These results can explain, at least qualitatively, the previously observed characteristic time and intensity dependence of light-induced refractive index changes in this type of waveguides. Both the time and temperature behaviour of the dark conductivity of all proton exchanged waveguides give strong evidence of ionic charge transport in the proton exchanged region.