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.     

Efficient coupling into polymer waveguides by gratings

Investigations of highly efficient grating couplers for polymer slab and strip waveguides fabricated by electron-beam lithography are reported. A maximum input efficiency of 67% is achieved. The electron-beam direct-writing technique allows one to replicate the original gratings into polymer substrates by embossing. An all-polymeric optical chip with efficient grating couplers is demonstrated. Waveguide grating couplers with blazed profile and variable grating depth are investigated. Thus, the intensity distribution of the outcoupled light is matched to a Gaussian-like profile. A focusing blazed grating that couples the light with an efficiency of 42% into a polymer strip waveguide is reported. A curvature correction of the grating lines allows one to improve the focusing properties.     

In vitro evaluation of borate-based bioactive glass scaffolds prepared by a polymer foam replication method

Borate-based bioactive glass scaffolds with a microstructure similar to that of human trabecular bone were prepared using a polymer foam replication method, and evaluated in vitro for potential bone repair applications. The scaffolds (porosity = 72 ± 3%; pore size = 250–500 μm) had a compressive strength of 6.4 ± 1.0 MPa. The bioactivity of the scaffolds was confirmed by the formation of a hydroxyapatite (HA) layer on the surface of the glass within 7 days in 0.02 M K₂HPO₄ solution at 37 °C. The biocompatibility of the scaffolds was assessed from the response of cells to extracts of the dissolution products of the scaffolds, using assays of MTT hydrolysis, cell viability, and alkaline phosphatase activity. For boron concentrations below a threshold value (0.65 mM), extracts of the glass dissolution products supported the proliferation of bone marrow stromal cells, as well as the proliferation and function of murine MLO-A5 cells, an osteogenic cell line. Scanning electron microscopy showed attachment and continuous increase in the density of MLO-A5 cells cultured on the surface of the glass scaffolds. The results indicate that borate-based bioactive glass could be a potential scaffold material for bone tissue engineering provided that the boron released from the glass could be controlled below a threshold value.     

电纺丝法制聚合物纳米纤维

主要介绍电纺丝法制聚合物纳米纤维的研究 ,以及所使用电喷雾沉积法 (ESD)装置和工艺及纳米纤维的应用。     

Fabrication of ridge waveguides: a new solgel route

Passive ridge waveguides can be deposited on silicon by a solvent-assisted lithographic process incorporating simple mask technology and photosensitive solgel-derived glasses. Thick films (~4 mum) are dip coated in one step, and channel waveguides and power splitters are imprinted in them by UV light through appropriate masks. Unexposed regions of the glass are removed by soaking of the films in n-propanol. The remaining ridges are then treated at 200 degrees C and planarized with a solgel cladding layer. Circular mode profiles are observed from ridge guides covered with the cladding. The waveguides are characterized with scanning electron microscopy, atomic force microscopy, surface profilometry, ellipsometry, and fiber end coupling. Overall, the procedure is simple and reproducible and leads to waveguides with low loss, of the order of 0.13 dB/cm.     

有机-无机复合材料光波导的制备

有机-无机复合光波导在光通信领域具有重要的应用价值,是目前的研究热点之一.采用溶胶-凝胶法分别制备了膜厚达13μm的光滑平整的PMMA膜和具有紫外感光性的膜厚为1.76μm的SiO2/ZrO2凝胶膜,研究了SiO2/ZrO2凝胶膜的感光性及紫外光照对两种薄膜折射率的影响.在此基础上,以PMMA膜为包层膜,SiO2/ZrO2凝胶膜为芯层膜,实现了光波导的包芯层复合.利用SiO2/ZrO2凝胶膜的感光性,结合紫外掩模技术,制备了条形的有机-无机复合光波导,理论分析表明该复合条形光波导能够实现入射波长为1.31μm,模数为0,1的传输.     

Thermal-structural modeling of polymer Bragg grating waveguides illuminated by a light emitting diode

This study reports both analytical and numerical thermal-structural models of polymer Bragg grating (PBG) waveguides illuminated by a light emitting diode (LED). A polymethyl methacrylate (PMMA) Bragg grating (BG) waveguide is chosen as an analysis vehicle to explore parametric effects of incident optical powers and substrate materials on the thermal-structural behavior of the BG. Analytical models are verified by comparing analytically predicted average excess temperatures, and thermally induced axial strains and stresses with numerical predictions. A parametric study demonstrates that the PMMA substrate induces more adverse effects, such as higher excess temperatures, complex axial temperature profiles, and greater and more complicated thermally induced strains in the BG compared with the Si substrate.     

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.     

Fabrication of polymer thin films with in-depth dye-dispersed structures by the vacuum spray method

We report the fabrication of polymer thin films with “in-depth” dye-dispersed structures using a vacuum spray method. Copper (II) 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine [(t-Bu)₄CuPc] and polycarbonate in chloroform solution were sprayed onto the substrate. The (t-Bu)₄CuPc distribution was controlled precisely during thin film growth by varying its concentration in the solution. Uniform, bilayer, and gradient structures of (t-Bu)₄CuPc dispersed in thin films were confirmed by high-angle annular dark field imaging on scanning transmission electron microscopy. The vacuum spray method has several advantages compared to the casting method, such as smaller dispersed dye-aggregates and lack of cavities due to air bubbles.     

Fabrication of nanosized alumina powders by a simple polymer solution route

Nanosized alumina (Al2O3) powders had been successfully fabricated by a simple polymer solution route employing polyvinyl alcohol (PVA) as an organic carrier. The fabricated alumina powders had an average particle size of 6.1 nm with a high specific surface area of 99.5 m2/g. As well, the alumina powders were fully crystallized to alpha phase at a relatively low temperature of 1000 degrees C. The PVA polymer contributed to a soft and porous microstructure of the calcined alumina powders, and ball-milling process with the porous powders was effective in making nanosized alumina powders. In addition, the content and degree of polymerization of the PVA affected the development of crystallization and powder properties. In this study, the simple polymer technique and milling process for the fabrication of nanosized alumina powders are introduced, and the effects of PVA on the property of the synthesized alumina powders are observed. For the study, the characterizations of the synthesized powders are conducted by using XRD, TEM, particle size analyzer, and nitrogen gas adsorption.     

Fabrication of a NicalonTM fiber/Si3N4-based ceramic-matrix composite by the polymer pyrolysis method

A processing route for ceramic matrix composites is developed based uponpolymer pyrolysis. Three types of Nicalon^TM fiber woven fabrics,—i.e., uncoated, carbon-coated, and carbon/SiC-coated—are impregnated with apolysilazane solution. Thus-formed prepregs are then cut, laminated,pressed and fired to 1000 °C in a nitrogen atmosphere. Upon pyrolysis,polysilazane converts to a Si₃N₄-based ceramic matrix with 60 wt% yield. The composites made with uncoated Nicalon^TM fibers have poor flexural andtensile strength (103 and 19 MPa, respectively) and show brittle fracturebehavior. That is due not only to the poor fiber-matrix interface but alsoto processing-induced fiber damage. For carbon and carbon/SiC-coatedNicalon^TM fiber composites, the coating layers on the fiber surfacemanipulate the appropriate fiber-matrix interface and also protect thefibers from damage during polymer pyrolysis, so these composites exhibithigher flexural (250 and 274 MPa, respectively) and tensile (138 and 196 MPa, respectively) strength. Also, the load stress-deflection behavior ofcomposites with two types of coated fibers cause noncatastrophic fracture.     

Fabrication of conjugated polymer nanowires by edge lithography

This paper describes the fabrication of conjugated polymer nanowires by a three stage process: (i) spin-coating a composite film comprising alternating layers of a conjugated polymer and a sacrificial material, (ii) embedding the film in an epoxy matrix and sectioning it with an ultramicrotome (nanoskiving), and (iii) etching the sacrificial material to reveal nanowires of the conjugated polymer. A free-standing, 100-layer film of two conjugated polymers was spin-coated from orthogonal solvents: poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) from chloroform and poly(benzimidazobenzophenanthroline ladder) (BBL) from methanesulfonic acid. After sectioning the multilayer film, dissolution of the BBL with methanesulfonic acid yielded uniaxially aligned MEH-PPV nanowires with rectangular cross sections, and etching MEH-PPV with an oxygen plasma yielded BBL nanowires. The conductivity of MEH-PPV nanowires changed rapidly and reversibly by >10 (3) upon exposure to I 2 vapor. The result suggests that this technique could be used to fabricate high-surface-area structures of conducting organic nanowires for possible applications in sensing and in other fields where a high surface area in a small volume is desirable.     

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 hollow waveguides for CO2 lasers

Germanium-coated metal (silver, gold, and copper) hollow waveguides for CO(2) laser energy delivery have been fabricated by electron-beam evaporation and plating techniques in which an acid-soluble glass mandrel with small surface roughness was used. The transmission characteristics of Ge-coated metal hollow waveguides were studied. Ge-coated Ag hollow waveguides showed smaller loss, 0.2 dBm, for CO(2) laser light than Ge-coated Au and Cu waveguides. The transmission characteristics of Ge-coated Ag hollow waveguides were measured in relation to a core diameter and a bending radius.     

Fabrication of a novel organic polymer thin film

Fabrication of organic polymer thin films and organic semiconductors are critical for the development of sophisticated organic thin film based devices. Radio Frequency plasma polymerisation is a well developed and widely used fabrication technique for polymer thin films. This paper describes the fabrication of an organic polymer thin film from a monomer based on Lavandula angustifolia. Several polymer thin films were manufactured with thicknesses ranging from 200 nm to 2400 nm. The energy gap of the polymer thin film was measured to be 2.93 eV. The refractive index and extinction coefficient was determined to be 1.565 (at 500 nm) and 0.01 (at 500 nm) respectively. The organic polymer thin film demonstrates the possibility of an environmentally friendly, cost effective organic semiconductor.     

Structure-based color of natural petals discriminated by polymer replication

The optical appearance of many flowers in nature relies on their inherent pigments ("chemical color") as well as on the surface structure of the epidermis ("structural color"). The structural color is created by a combination of regular and irregular micro- and nanosized features. With a red rose petal as a biological template, we have separated the structural coloration from the chemical coloration by reproducing the petal's intricate surface structure in a pigment-free polymer. UV-vis reflectance measurements of the templates showed that the pigment-induced chemical coloration of the red-rose petal results in intense absorption and reflection in the green (～550 nm) and red (～700 nm) spectral region, respectively. The micro- and nanosized structural hierarchy on the petal surface, on the other hand, induced a modulation of the optical reflectivity and a filtering effect in specific wavelength ranges. More notably, we observed that a variation in the size of the micro/nanostructures on the petal surface leads to an effective modulation of the reflectance. These results could provide useful tips for the design of bioinspired optical devices, emulating natural petal structures.     

紫外光刻法制备图案化聚合物纳米管/线阵列的研究

探讨了紫外光刻技术制备图案化聚合物纳米管/线阵列的方法,研究制备过程中的各种影响因素,并找到了最佳的实验条件。采用溶液浸润法,成功制备了不同图案的聚合物纳米结构阵列。溶液浓度为6%(质量分数),得到的是聚合物纳米管阵列;溶液浓度为10.0%(质量分数),得到的是聚合物纳米线阵列。     

Fabrication of CuTAPc polymer nanowires and nanotubes by electropolymerization

Poly-copper tetraaminophthalocyanine (CuTAPc) nanowires and nanotubes were successfully fabricated on porous alumina templates by electropolymerization and characterized using field-emission scanning electron microscopy (FE-SEM), energy-dispersive x-ray spectroscopy (EDX), transmission electron microscopy (TEM) and Raman microscopy. The lengths of these nanostructures could be controlled by the number of cycles applied and the monomer concentrations, while their diameters are confined by the pore size of the template. The product of electropolymerization (whether as nanowires or nanotubes) is a function of the monomer concentrations. The morphology of electropolymerized nanowires was found to be sensitive to the changes in scan rates and monomer concentrations. These organometallic nanostructures may have applications in micro-electronics, chemical sensing, and catalysis.