Optimized design of polarization-independent and temperature-insensitive broadband optical waveguide coupler by use of fluorinated polyimide

A statistically optimized design method suitable for a polariation-independent and temperature-insensitive broadband waveguide coupler is proposed. By use of this method, a fluorinated polyimide waveguide 3-dB waveguide coupler for 1490 to approximately 1610 nm application is designed by optimizing polarization and temperature fluctuation. The validity of the design is verified through simulation based on the three-dimensional beam propagation method (3D-BPM), which revealed a coupling ratio of 50 +/- 0.8% in a 120-nm bandwidth in the temperature range -10 to 40 degrees C for both orthogonal polarizations.     

TiO2 nano-particle-dispersed polyimide composite optical waveguide materials through reverse micelles

Optically transparent polyimide : titanium dioxide (TiO2) composite waveguide materials were prepared by the dispersion of nano-sized TiO2 particles into polyimide. The particles were produced through reverse micelles using the sol–gel method, and were dispersed into the fluorinated polyimide solution. The solution was coated on a glass substrate, and a polyimide : TiO2 composite waveguide (4 wt% TiO2 concentration) was successfully produced after the heat treatment. Because the particle size was very small, no noticeable scattering loss was observed in the resultant slab waveguide. The measured optical propagation loss at 633 nm was 1.4 dB cm-1. It is equivalent to that of the pure polyimide, and the refractive index was increased from 1.550 to 1.560 by the incorporation. This revised version was published online in November 2006 with corrections to the Cover Date.     

Channel-optical-waveguide fabrication based on electron-beam irradiation of polyimides

A new-channel-waveguide-fabrication process for use with polyimide is described. The new technique uses an electron-beam-induced effect to alter the refractive index of the polyimides directly. Channel waveguides with an 8-μm-wide, 8-μm-deep core have been fabricated on a polyimide film by the use of electron-beam irradiation. Only one kind of polyimide (6FDA/TFDB) was used in this waveguide. The difference in refractive index between the core and the cladding was approximately 0.30% for both TEand TM-polarized incident light when the dose was 1500 μC/cm(2), which was sufficient to produce waveguides. The optical properties of the waveguide are also demonstrated.     

Moisture-induced drift in thermo-optic phase shifters composed of deuterated and fluorinated methacrylate polymer waveguides

Using deuterated and fluorinated methacrylate polymer waveguides, we fabricated thermo-optic phase shifters that require a small electric power of 10 mW to cause a pi phase shift. The phase shifters had a phase drift that was greater at higher humidity and that was saturated in approximately 10 min. This phenomenon is ascribed to the moisture desorption-sorption of the waveguide polymers caused by heating-cooling on the basis of experimental results on the relationships among waveguide temperature increase, relative humidity, and moisture sorption of the waveguide polymers. This conclusion is supported by the calculation of temperature and moisture distribution in the waveguide when the thin-film heater is heated.     

Molecular design and synthesis of branched bichromophore-attached linear fluorinated polyimides for nonlinear optical applications

A branched structure bichromophore was developed to increase the nonlinearity of optical polymers. The branched bichromophore was incorporated into the polymer backbone to prepare a novel nonlinear optical (NLO) side-chain fluorinated polyimide with high optical nonlinearity and good thermal stability. The novel nonlinear optical side-chain fluorinated polyimide exhibits a large electro-optic (E-O) coefficient (γ₃₃) (34 pm/V at 1550 nm) which is larger than that of the conventional side-chain optical polyimide. This is mainly attributable to an increased chromophore concentration and high polarizing efficiency derived from the branched structure. The branched structure of the bichromophore is incorporated into a polymer backbone to result in a high chromophore concentration. Moreover, the three-dimensional (3D) architecture and large molecular size of the branched bichromophore can spatially shield from strong interchromophore electrostatic interactions to enhance the poling efficiency. The side-chain fluorinated polyimide exhibits excellent solubility in common organic solvents, good film-forming property, high glass-transition temperature (T _g) (190 °C) and thermal stability up to 235 °C.     

Photo-induced liquid crystal alignment of poly(vinyl cinnamate) and fluorinated polyimide blends

Liquid crystal(LC) alignment properties were mainly affected by surface properties of alignment layers. In our previous work, we prepared poly(vinyl cinnamate) (PVCi) and polyimide blend alignment layer for thermally stable LC alignment. In this work, we utilized fluorinated polyimide for blend alignment layers in order to modify surface properties of alignment layers. For this purpose, polyimides containing fluorine unit were synthesized and used for the blend alignment layers. Fluorine containing diamine, 4,4′-bis[2-(4-aminophenyl)hexafluoropropyl]-diphenyl ether(BDAF), is used for the polyimide synthesis. We prepared the fluorinated polyimide and PVCi blend alignment layers and investigated the effect of fluorine on the LC alignment properties and pretilt angle of LC.     

Optimized design of fluorinated polyimide based interleaver

Statistical optimization method for the design of a fluorinated polyimide wavelength division element for optical communication is proposed. The opitimized device is an interleaver element suitable for dividing over 40 wavelengths in the 1550 nm band. Optimization considers the inherent polarization dependence of fluorinated polyimide based on measurements of the dispersion characteristics and birefringence of fluorinated polyimide film. A 40-wavelength device is designed by use of the proposed technique for a working wavelength of 1550 nm and a wavelength interval of 0.8 nm. The device exhibited a 1-dB passband of 0.5 nm and a 3-dB passband of 0.8 nm, and output wavelength fluctuation due to polarization effects of less than 0.08 nm.     

Monolithic-integrated microlaser encoder

We have developed an extremely small integrated microencoder whose sides are less than 1 mm long. It is 1/100 the size of conventional encoders. This microencoder consists of a laser diode, monolithic photodiodes, and fluorinated polyimide waveguides with total internal reflection mirrors. The instrument can measure the relative displacement between a grating scale and the encoder with a resolution of the order of 0.01 mum; it can also determine the direction in which the scale is moving. By using the two beams that were emitted from the two etched mirrors of the laser diode, by monolithic integration of the waveguide and photodiodes, and by fabrication of a step at the edge of the waveguide, we were able to eliminate conventional bulky optical components such as the beam splitter, the quarter-wavelength plate, bulky mirrors, and bulky photodetectors.     

Surface modification of a flexible polyimide film using a reactive fluorinated polymer nanosheet

This paper describes an effective approach to surface modification of a flexible polyimide film using a reactive fluorinated polymer nanosheet. N-(1H,1H-pentadecafluorooctyl)methacrylamide copolymers containing carboxyl group as a reactive moiety form stable monolayer on the water surface and highly ordered reactive polymer nanosheets can be fabricated by the Langmuir-Blodgett technique. This reactive fluorinated polymer nanosheet was utilized to modify the surface properties of polyimide film through its immobilization using thermal treatment. The modification process was studied by X-ray photoelectron spectroscopy (XPS) and modified PI surface was characterized by contact angle measurements and atomic force microscopy (AFM).     

Widely tunable optical bandpass filter by use of polymer long-period waveguide gratings

We report the design and fabrication of a widely tunable optical bandpass filter based on using two identical long-period gratings formed along a polymer channel waveguide with a section of the waveguide core removed. The peak transmission of the passband of the fabricated filter is approximately 60% and the bandwidth of the passband is approximately 6 nm. The filter is thermally tunable over the C + L band (1520-1610 nm) for both TE and TM polarizations with a temperature control of approximately 30 degrees C.     

芳香族聚酰亚胺泡沫的隔热性能研究

利用DMTA和自制热导测试仪测试了4种自制芳香族聚酰亚胺泡沫的玻璃化转变温度(Tg )、静态温度下的热导率(λ)和动态温度作用下的隔热性能;分析了一定厚度的聚酰亚胺泡沫的密度和温度影响热导率的规律;考察了聚酰亚胺泡沫在动态温度下的隔热性能.结果表明:单体(尤其是二胺)刚性越大,聚酰亚胺泡沫的玻璃化转变温度越高;在密度为50～140kg/m3范围内,聚酰亚胺泡沫的密度对热导率的影响较小;在温度为50～350℃范围内,温度的升高使聚酰亚胺泡沫的热导率增加;在动态温度下,聚酰亚胺泡沫表现出明显的热滞后性.     

A polyimide-based flexible monopole antenna

Journal of Materials Science: Materials in Electronics - A polyimide (PI)-based flexible monopole antenna fed by coplanar waveguide (CPW) was fabricated by self-assembly technology. The measured...     

Fluorinated polyimide–silica films with low permittivity and low dielectric loss

A sol–gel process was used to prepare polyimide–silica hybrid films from the fluorinated polyimide precursors (6FDA-ODA) and tetraethylorthosilicate (TEOS) in N,N-dimethyl acetamide. The hybrid film was then treated with hydrofluoric acid to remove the dispersed silica particles, leaving inside the film pores with diameters ranged from 80 nm to 1 μm, which depended on the size of the silica particles. The chemical structures and morphology of the hybrid and porous films were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The synthesized porous fluorinated polyimide films show low relative dielectric permittivity of 1.9, rendering them promising for microelectronic packaging materials.     

Formation of channel waveguide with grating in polymer films based on simultaneous photobleaching and embossing

Channel waveguide with grating is fabricated in nonlinear optical (NLO) polymer thin films by means of simultaneous embossing and photobleaching. A combined structure of mask/master consisting of a photomask part and a grating die part which is made of polyimide is fabricated. Then the mask/master is set on the NLO polymer films and both embossing and photobleaching are performed simultaneously. Profiles of the replica grating and the channel waveguide are estimated.     

Ozonolysis of functionalized single-walled carbon nanotubes

Room temperature ozonolysis of fluorinated SWNT and phenyl-sulfonated SWNT have been studied in perfluoropolyether (PFPE) solvents. Etching at the end caps (approximately 70 nm/hour for fluorinated SWNT/PFPE suspension with 1 g/l concentration) has been demonstrated to be the dominating effect during the ozonolysis of fluorinated SWNT. Base on characterization by AFM analysis, X-ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy, fluorination along the SWNT sidewalls protects F-SWNT from extensive functionalization by ozonolysis. An ozone reaction with fluorinated SWNT has been found to improve its solubility in 96% sulfuric acid. This allows oxidative cutting by ammonium peroxydisulfate without defluorination. In comparison to fluorinated SWNT, phenyl-sulfonated SWNT was found to be effectively and homogeneous cut by ozonolysis in a water suspension.     

含戊二烯酮结构新型光敏聚酰亚胺的合成与表征

用4,4’-(六氟亚异丙基)-邻苯二甲酸酐(6FDA)与光敏性二胺1,5-二(氨基苯基)-1,4-戊二烯-3-酮(BAPO)合成新型的可溶性光敏聚酰亚胺(PSPI)。用FT-IR,1H-NMR,GPC对聚合物进行了表征,同时对聚合物的溶解性能、热性能和光敏性能进行了探讨。结果表明,所合成的聚合物在常见的有机溶剂DMF、NMP和DMSO中,显示了极好的溶解性能;具有优良的热稳定性能,其玻璃化温度为268℃,5%的热失重率的温度为467℃;聚合物的感光性通过UV-Vis光谱进行了研究。     

基于离子交换与激光打印技术在含氟聚酰亚胺薄膜表面制备银-铜金属线

以4,4’-六氟亚异丙基-邻苯二甲酸酐(6FDA)和4,4’-二胺基二苯醚(4,4’-ODA)为原料制备了含氟聚酰亚胺薄膜,然后通过水解、激光打印、离子交换、化学还原等技术得到银和铜双金属的图案化聚酰亚胺薄膜。通过X-射线衍射仪、四点探针测试仪、光学显微镜、扫描电子显微镜等仪器系统研究了薄膜表面金属的形成过程及水解时间与导电性的关系。实验结果表明,随着水解时间的增加,金属线条的导电性逐渐增加,电导率最大达到500s/cm。     

Design, fabrication, and performance of preferential-order volume grating waveguide couplers

Both a nonfocusing and a focusing preferential-order volume grating waveguide coupler were designed, fabricated, and tested. These volume grating couplers are designed to outcouple a 633-nm wave guided in an adjacent polyimide waveguide film. The slanted-fringe volume gratings are recorded holographically by the interference of two 364-nm waves. The dynamics of the holographic photopolymer HRF600X001 are investigated in relation to the interaction with the guided wave. The fabricated couplers exhibited a preferential coupling of 98%, a spatial coupling rate of 3.6 mm(-1), and a coupling efficiency of 95%. The focusing grating coupler focused the outcoupled beam to a focal line with a full width at half-maximum of 10.49 mum located 25 mm above the grating.     

Preparation, morphology and properties of acylchloride-grafted multiwall carbon nanotubes/fluorinated polyimide composites

A fluorinated polyimide (PI) was synthesized by a two-step reaction from 4,4′-(hexafluoroisopropylidene) diphthalic anhydride and 2,2′-bis(trifluoromethyl)-4,4′diaminobiphenyl. A series of PI composites with various mass fractions of multi-walled carbon nanotubes (MWNTs) were prepared by either an in situ polymerization or blending process. To increase the chemical compatibility of carbon nanotubes with the PI matrix, MWNTs were treated with an acid mixture and sulfoxide chloride by turns. Results show that the dispersion of the MWNTs is highly improved in the PI by modification. The modified MWNTs are dispersed homogeneously in the matrix, while the structures of the PI and MWNTs are stable in the preparation process. The thermal stability of the nanocomposites is slightly lower than that of the pure PI. With incorporating MWNTs, the storage modulus and glass transition temperature of the composite films enhanced comparing to that of PI matrix. The dielectric constants of the composites increase sharply, which is favorable to their practical use in anti-static materials and embedded capacitors.     

Fabrication of CuO and Cu2O nanoparticles in a thick polyimide film by post heat treatment in a controlled-atmosphere

We investigated the formation of CuO or Cu2O nanoparticles in the thick polyimide films by oxidizing Cu nanoparticles at various temperatures during the post heat-treatment. Cu nanoparticles of 4-5 nm in diameter were initially formed in the polyimide film by the reaction between a Cu film and a polyimide precursor, polyamic acid, and a following thermal curing in a reducing atmosphere. After the subsequent post heat-treatments in oxidizing atmospheres, X-ray diffraction patterns revealed that initial metallic Cu nanoparticles were transformed to Cu2O or CuO nanoparticles depending on the temperature during the post heat-treatment. Cu nanoparticles were oxidized to Cu2O during the post heat-treatment at low temperature while Cu nanoparticles were oxidized to CuO during the post heat-treatment at high temperature. Cross-sectional TEM studies showed that about 4.7 nm sized Cu2O nanoparticles or 4.7-5.2 nm sized CuO nanoparticles were fabricated in a thick polyimide film depending on the post heat-treatment condition. In the optical absorption measurements, the absorption peak from surface plasmon resonance of Cu nanoparticles disappeared during the post heat-treatment in an oxidizing atmosphere.