溶胶-凝胶法制备有机-无机杂化光波导材料研究进展

有机-无机杂化材料因同时具有有机功能基团和无机功能基团的结构特点而易于有机光活性物质和无机活性物质的掺杂已被人们广泛关注和大力研究.溶胶-凝胶法是制备有机-无机杂化光波导材料的主要方法.阐述了溶胶-凝胶法制备杂化材料的原理,比较了几种目前研究得较多的有机-无机杂化光波导材料体系,指出了各自的优缺点,介绍了杂化材料制备光波导器件的工艺流程,最后归纳了溶胶-凝胶法制备有机-无机杂化光波导材料过程中存在的问题.     

原位聚合制备有机-无机复合材料的研究进展

综述了原位聚合有机-无机纳米材料的制备方法,其中包括聚合物与纳米SiO2的复合,聚合物与层状硅酸盐纳米材料的复合,聚合物与纳米TiO2复合以及聚合物与其它纳米粒子的复合等方面的研究进展;较详细介绍了其发展现况和存在的问题,并对制备方法进行了展望.     

无机/有机PMMA复合材料最新研究进展

无机/有机PMMA复合材料以其优异的性能越来越受到人们的关注。综述了SiO2/PMMA复合材料、TiO2/PMMA复合材料、Fe3O4/PMMA复合材料、ZrO2/PMMA复合材料及水滑石/PMMA等复合材料的制备方法及性能,并对无机/有机PMMA复合材料的发展进行了展望。     

有机波导制备工艺对乐甫波传感器性能的影响

研究了基于PMMA波导的乐甫波传感器,研究了器件的插损以及质量灵敏度随波导层厚度变化的关系.采用低浓度、低粘度的前驱溶液,多步旋涂工艺制备了PMMA波导薄膜,降低了器件的插损,实现了2.18/μm的"有效厚度",器件的质量灵敏度达705cm2/g,与前人相比提高了1倍.     

平面光波导膜的ECR—PECVD制备及特性研究

采用微波电子回旋共振等离子体增强化学气相沉积技术，在单晶硅衬底上制备了用于平面光波导的ＳｉＯ２薄膜研究了沉积速率与工艺参数之间的，并对身频偏置对成膜特性的影响作了初步实验研究。通过Ｘ射线光电子能谱、傅立叶变换红外光谱、扫描电镜、原子力显微镜、以及扫措隧道显微镜三维形貌和椭偏仪等测量手段，分析了样品的薄膜结构和光学特性等。结果表明，在较低温度下沉积出均匀致密、性能优良的ＳｉＯ２薄膜。此外，还成功制备     

溶胶-凝胶法制备SiO2/ZrO2无机复合膜的研究

以硅酸乙酯和氧氯化锆为先驱体,用乙醇为溶剂,采用溶胶--凝胶法于室温下在Al2O3基体上制备了ZrO2/SiO2无机复合膜.重点考察了涂膜温度、ZrOCl2摩尔百分含量、溶胶浓度及添加剂对膜性能的影响.结果表明:在较高的温度下涂膜可以提高膜的性能;ZrOCl2的存在对渗透比的影响不大,但能够提高溶胶的交联度,从而提高制膜效率,同时也有利于渗透通量的提高;采用浓溶胶和稀溶胶结合的方式涂膜不但可以提高制膜效率,还可以提高膜的性能.添加剂TEABr能够均化膜孔径,提高膜的性能.     

低损耗离子交换玻璃基光波导制备与分析

考虑到离子交换和离子扩散工艺的特殊要求, 设计并熔制了适合于离子交换工艺的硅酸盐玻璃材料SiO₂-B₂O₃-Al₂O₃-R’O-R₂O（R’=Ca, Mg; R=Na, K）. 采用Ag⁺/Na⁺熔盐离子交换和电场辅助离子扩散工艺在这种玻璃材料基片上获得了掩埋式条形光波导. 光学显微镜和电子探针分析表明高折射率的Ag⁺扩散区位于玻璃基片表面以下约10μm处, 形成光波导的芯部. 光波导芯部尺寸约为8μm×8μm, 与单模光纤芯径尺寸相当, 保证了较低的光纤耦合损耗. 对光波导的测量结果得出：在波长为1.5μm处条形光波导的传输损耗约为0.1dB/cm, 与单模光纤的耦合损耗约为0.2~0.3dB. 条形光波导的传输损耗与材料本身的损耗接近, 表现出掩埋式光波导的低损耗特征. 分析表明, 经过进一步优化, 这种光波导制备技术可用于低损耗光波导器件的制作.     

PMMA/纳米SiO2纳米复合材料的制备和界面研究

用硅烷偶联剂KH570对纳米SiO2进行修饰改性,采用原位分散聚合法制备了PMMA/纳米SiO2纳米复合材料,用溶解实验、力学性能、SEM和DMA等方法对纳米SiO2粒子和PMMA基体之间的界面相容性进行了表征和研究,由拉伸强度计算出来界面相互作用参数B.结果表明:SiO2在基体中可能起到了交联点的作用;改性后的氧化硅与聚合物基体形成强的界面结合;随着纳米粒子含量的增加,粒子和聚合物基体之间有效的界面相互作用越强.     

UV/Vis visible optical waveguides fabricated using organic-inorganic nanocomposite layers

Nanocomposite layers based on silica nanoparticles and a methacrylate matrix are synthesized by a solvent-free process and characterized in order to realize UV/Vis transparent optical waveguides. Chemical functionalization of the silica nanoparticles permits to interface the polymers and the silica. The refractive index, roughness and wettability and the machinability of the layers can be tuned changing the silica nanoparticle concentration and chemical modification of the surface of the nanoparticles. The optical transparency of the layers is affected by the nanoparticles organization between the organic chains, while it increased proportionally with respect to silica concentration. Nanocomposite layers with a concentration of 40 wt% in silica reached UV transparency for a wavelength of 250 nm. UV/Vis transparent waveguides were micromilled through nanocomposite layers and characterized. Propagation losses were measured to be around 1 dB cm(-1) at a wavelength of 350 nm.     

Fabrication of chirped gratings on GaAs optical waveguides

After a brief review of the applications and fabrication techniques of gratings in integrated and guided wave optics, a new method of fabricating chirped gratings is presented. The method is based on the interference of two spherical laser beams after spatial filtering by pinholes. The experimental conditions required for fabricating antisymmetric linearly chirped gratings, symmetric quadratically chirped gratings and uniform gratings are presented by way of example. By this method chirped gratings with small variations in the period can be fabricated on GaAs thin film optical waveguides. Profiles and patterns of chemically etched corrugations are quite uniform, mainly because of the direct interference of beams immediately after spatial filtering.     

Fabrication of photo-cross-linked stable organic-inorganic hybrid second-order nonlinear optical films

A photo-cross-linked stable organic-inorganic hybrid second-order nonlinear optical (NLO) film was fabricated by sol-gel process with silicon sol linking aromatic diazonium group (SOD) and Chromophore molecule 2-({4-[4-(2-carboxy-2-cyano-vinyl)-phenylazo]-phenyl}-methyl-amino)-ethyl acid (DRCB). The films were poled under 50 DC voltage electric field at room temperature at the existence of solvents. After the solvents volatilized completely and upon UV irradiation under the electric field, the ionic bonds converted to stable covalent bonds in the system, the orientations of the chromophores were fixed by the photo-cross-linked structures. The order parameter of the fabricated film can retain 99% after 17 days at room temperature. The stable organic-inorganic hybrid photo-cross-linked NLO films fabricated in this paper had large potential to be applied in electric-optic devices.     

Fabrication of polymer waveguides between two optical fibers using spatially controlled light-induced polymerization

A new method for the fabrication of polymer waveguides between two optical fibers using a spatially controlled photopolymerization is reported. By taking advantage of the self-guiding effect of light through a photopolymerizable medium, polymer waveguides perfectly aligned with the fiber cores and strongly anchored to their surfaces are fabricated. The process is characterized by following in situ the coupling efficiency of a nonactinic laser source. Examples of waveguides exhibiting good coupling efficiency and high flexibility are given. By selecting the suitable monomers and adjusting the photonic parameters, the optical and mechanical waveguide properties (diameter, length, refractive index, rigidity, and flexibility) can be controlled in view of optical sensor applications.     

Fabrication of channel waveguides from sol-gel-processed polyvinylpyrrolidone/ SiO(2) composite materials

Sol-gel-processed composite materials of polyvinylpyrrolidone (PVP) and SiO(2) were studied for optical waveguide applications. PVP is a polymer that can be crosslinked, so it is expected to have high thermal stability after crosslinking. However, thermal crosslinking and thermal decomposition of pure PVP take place around the same temperature, 200 °C, therefore pure PVP had a high optical propagation loss as a result of the absorption of the decomposed molecules after crosslinking. The incorporation of sol-gel-processed SiO(2) prevented the thermal decomposition of PVP and provided remarkably low optical propagation losses. The PVP/SiO(2)composite material also produced thick (>2-μm) crack-free films when the PVP concentration was 50% or higher. An optical propagation loss of 0.2 dB/cm was achieved at 633 nm in the 50% PVP/SiO(2) composite planar waveguide. Several aspects of the thermal stability of the waveguides were evaluated. The slab waveguide was then used for fabrication of channel waveguides with a selective laser-densification technique. This technique used metal lines fabricated with photolithography on the slab waveguide as a light absorbent, and these metal lines were heated by an Ar laser. The resultant channel waveguide had an optical propagation loss of 0.9 dB/ cm at 633 nm. This technique provides lower absorption loss and scattering loss compared with the direct laser-densification technique, which uses UV lasers, and produces narrow waveguides that are difficult to fabricate with a CO(2) laser.     

Dip-coated thin-film polycarbonate optical waveguides

We report on our systematic and detailed study of fabrication and characterization of polycarbonate thin-film optical waveguides. Various waveguide properties, such as refractive index, optical loss, waveguide thickness, dispersion as a function of temperature of waveguides and substrates, and the effect of thickness gradient on optical guiding losses, have been reported. A comparative study of the properties of waveguides fabricated with dioxane and tetrahydrofuran as solvents is also presented.     

Polymer-based waveguides and optical switching

The fabrication and linear optical characterization of a Bragg reflector in a planar polymeric waveguide, suitable for an all-optical switching device, is reported. Surface corrugation gratings with a grating constant of 349 nm were produced in different polymeric films of poly(phenylene-vinylene), polydiacetylene and polystyrene by excimer laser photoablation. Furthermore, the gap in the linear transmission spectrum of the modulated waveguide was measured and compared with the result of numerical simulations. A good agreement can only be found if a non-uniform grating with a small chirp is assumed. This small deviation from the uniform grating cannot be resolved with a scanning electron microscope. However, this linear optical investigation helps to further improve the fabrication process and opens the possibility to yield a well-defined grating with a prescribed modulation strength, which is a vital requirement for the proper operation of a nonlinear all-optical switch.     

Modeling photobleached optical polymer waveguides

One of the most efficient ways to prepare nonlinear optical polymer channel waveguides is by photobleaching. To control the index profile precisely and to design and improve the performance of active electro-optical devices, modeling of the photobleaching process is important. We report our phenomenological bleaching model, which uses a stretched exponential time dependency technique that predicts the index profile for polymer channel waveguides and present design rules for active optical switches and modulators. One way to verify the bleaching model is to calculate the effective index and compare this with our measured effective index obtained with prism-coupling techniques. The bleaching model shows good agreement with experiments.