Lensed-taper launching coupler for small-bore, infrared hollow fibers

A new type of launching coupler for small-bore, hollow fibers, consisting of a lens and a tapered hollow waveguide, is proposed to increase the alignment tolerance between an input laser beam and small bore fibers. First, we designed the structural dimensions of the coupler by using a ray-tracing method. Then, a series of experiments employing tapered hollow waveguides made of Pyrex glass was performed to investigate the effectiveness of the new coupler. It is shown that the coupler has a high efficiency with attenuation of around 0.5 dB, especially when the inside of the taper section is coated with a polymer and silver film. In addition, we also show that the coupler has great tolerance for the transverse displacement of a waveguide axis, which gives a 0.1-dB loss increase for a 300-mum displacement.     

Highly efficient coupling of photons from nanoemitters into single-mode optical fibers

Highly efficient coupling of photons from nanoemitters into single-mode optical fibers is demonstrated using tapered fibers. A percentage (7.4 ± 1.2%) of the total emitted photons from single CdSe/ZnS nanocrystals were coupled into a 300 nm diameter tapered fiber. The dependence of the coupling efficiency on the taper diameter was investigated and the coupling efficiency was found to increase exponentially with decreasing diameter. This method is very promising for nanoparticle sensing and single-photon sources.     

介质(Ag/AgI)镀层空芯玻璃光纤的制备及红外传输性能的研究

介质（Ａｇ／ＡｇＩ）镀层空芯玻璃光纤是一种较好的传输红外激光的柔性光纤材料．采用液相化学沉积法成功地制备了内径分别为１．０、０．５３、０．３２ｍｍ,长度为１．５ｍ的介质（Ａｇ／ＡｇＩ）镀层玻璃空芯光纤．利用傅里叶红外光谱仪和 ＬＪＬ－３５Ａ ＣＯ_２激光器分别测试了介质（Ａｇ／ＡｇＩ）镀层玻璃空芯光纤的传输损耗,测试结果表明：介质（Ａｇ／ＡｇＩ）镀层空芯玻璃光纤在２．５～２０μｍ波长范围内有较低的损耗值;随着光纤内径（α）的增大,空芯光纤的传输损耗（α）降低,这与Ｍｉｇａｇｉ理论（α　∝１／α^３）相符合．另外,由于光纤的注入端头发热致使介质（Ａｇ／ＡｇＩ）镀层空芯玻璃光纤的传输损耗随注入功率的增加而增大．     

Chalcogenide double index fibers: fabrication, design, and application as a chemical sensor

Double index chalcogenide fibers, based on tellurium, arsenic, and selenium, have been made by an original technique. This technique, based on the build-in-casting method, is achieved in a sealed silica ampoule. In view of the low attenuation obtained in the mid-infrared (IR), these fibers are used to implement Fiber Evanescent Wave Spectroscopy (FEWS). As the IR light is only propagated through the core of the waveguide, a chemical etching is applied in order to remove the glassy cladding of the sensing zone. IR spectra of ethanol and chloroform, recorded with such sensor, are presented showing the high sensitivity of the method.     

多根光纤衰减变化自动监测的实现

针对光纤衰减变化常用的后向散射监测法和传输功率监测法存在的不足,提出了一种自动监测多根光纤衰减变化的方法。首先将多根光纤串联焊接,再利用计算机所编制的软件,控制光时域反射仪(OTDR)对所焊接的光纤串上的每根光纤逐段进行测试,从而实现对多根光纤的衰减变化的自动测试。该方法成本低廉,测试精度和工作效率大为提高。     

Experimental evaluation of a hollow glass fiber

Very high interest in making a low-loss fiber for the infrared has been stimulated by important applications in optical communication, surgery, cutting, welding, and heat treatment. The leaky waveguide is one of the most promising types of future fiber in the infrared region where low-loss materials are not available or not suitable for making fibers (i.e., CO2 laser light lambda = 10.6 microm). In this paper a comparative model of a He-Ne laser beam and an oxide glass leaky hollow fiber for a CO2 laser light beam and a chalcogenide glass leaky hollow fiber are studied. Measurements of attenuation, dependence of output power on diameter and angle, and the angular dependence of output angle vs input angle were made. The experimental data were compared with theoretical calculations, and the critical value of the wall thickness for minimum attenuation is given.     

Attenuation Scale Calibration of an Optical Time Domain Reflectometer Using an External Laser Source

Optical time domain reflectometers (OTDRs) are widely used to measure the attenuation of optical fibers. Accurate measurement of the attenuation requires periodic calibration of OTDRs. In this paper, a system is proposed based on the external source method (ESM) to calibrate of the attenuation scale of an OTDR over a dynamic range of around 15 dB. The ESM method has several advantages over the widely-used standard reference fiber (SRF) since it is fast, can be automated and offers direct traceability to the SI units. In order to estimate the accuracy of the proposed setup, an OTDR has been calibrated using the SRF and the ESM methods. The calibration uncertainty of the ESM method is found to be 0.040 dB, which is similar to that of the SRF method which is found to be 0.038 dB.     

Simulation Guided Coaxial Electrospinning of Polyvinylidene Fluoride Hollow Fibers with Tailored Piezoelectric Performance

Electrospun polyvinylidene fluoride (PVDF) piezoelectric fibers have high potential applicability in mechanical energy harvesting and self-powered sensing owing to their high electromechanical coupling capabilities. Strategies for tailoring fiber morphology have been the primary focus for realizing enhanced piezoelectric output. However, the relationship between piezoelectric performance and fiber structure remains unclear. This study fabricates PVDF hollow fibers through coaxial electrospinning, whose wall thickness can be tuned by changing the internal solution concentration. Simulation analysis demonstrates an increased effective deformation of the hollow fiber as enlarging inner diameter, resulting in enhanced piezoelectric output, which is in excellent agreement with the experimental results. This study is the first to unravel the influence mechanism of morphology regulation of a PVDF hollow fiber on its piezoelectric performance from both simulation and experimental aspects. The optimal PVDF hollow fiber piezoelectric energy harvester (PEH) delivers a piezoelectric output voltage of 32.6 V, ≈3 times that of the solid PVDF fiber PEH. Furthermore, the electrical output of hollow fiber PEH can be stably stored in secondary energy storage systems to power microelectronics. This study highlights an efficient approach for reconciling the simulation and tailoring the fiber PEH morphology for enhanced performances for future self-powered systems.     

Analysis of an upside-down taper lens end from a single-mode step-index fiber

We introduce and analyze the upside-down taper lens end drawn from step-index fibers. Also, we model the refractive-index distribution and present the ABCD transformation matrix of this fiber end under paraxial approximation. The analysis can be useful for designing micro-optic image systems and laser diodes to single-mode fiber coupling optics.     

A Two Coupler Method for Measurement of Complex Permittivity of Dielectric Materials at Microwave Frequencies

This paper describes two coupler method for measurement of dielectric properties of materials, at microwave frequencies. Two waveguide sections, fed from a common source, are coupling power into a waveguide filled with dielectric. The phase and attenuation constants are computed from the values of phase and attenuation adjustment required for cancellation of the signal in the dielectric filled waveguide. The two coupler method is particularly applicable for measurements of dielectric properties of aerosols and gases.     

Al2O3‐Assisted Confinement Synthesis of Oxide/Carbon Hollow Composite Nanofibers and Application in Metal‐Ion Capacitors

Hollow micro‐/nanostructures are widely explored for energy applications due to their unique structural advantages. The synthesis of hollow structures generally involves a “top‐down” casting process based on hard or soft templates. Herein, a new and generic confinement strategy is developed to fabricate composite hollow fibers. A thin and homogeneous atomic‐layer‐deposition (ALD) Al₂O₃ layer is employed to confine the pyrolysis of precursor fibers, which transform into metal (or metal oxide)–carbon composite hollow fibers after removal of Al₂O₃. Because of the uniform coating by ALD, the resultant composite hollow fibers exhibit a hollow interior from heads to ends even if they are millimeter long. V, Fe, Co, and Ni‐based hollow nanofibers, demonstrating the versatility of this synthesis method, are successfully synthesized. Because of the carbon constituent, these composite fibers are particularly useful for energy applications. Herein, the as‐obtained hollow V₂O₃–C fiber membrane is employed as a freestanding and flexible electrode for lithium‐ion capacitor. The device shows an impressive energy density and a high power density.     

Modelling,design and optimization of compact taper and gratings for mode coupling to SOI waveguides at C-band

In this work, the design and optimization of compact taper is presented to enable coupling of infrared light in the C-band with the nano-photonic silicon-on-insulator (SOI) integrated optical waveguide. The proposed compact taper results in ～96% transmission efficiency for the taper length of ～5?µm and ～99.5% transmission efficiency for the taper length of 10?µm. The use of the proposed compact taper significantly reduces the foot print of optical coupler (grating and proposed compact taper) to (10?×?5)?µm² with ～96% transmittance and (10?×?10)?µm² with ～99.5% transmittance. The end-to-end coupling loss is less than 0.01?dB in the C-band. The compact taper along with grating presented in this work can be used as an efficient optical coupler for mode coupling from fibre to SOI single-mode optical waveguide in high density optical integrated circuits operating at 1550?nm.     

Development and optimization of a mid-infrared hollow waveguide gas sensor combined with a supported capillary membrane sampler

A gas sensor for application in water analysis was developed by combination of a mid-infrared (MIR) hollow waveguide with a Fourier transform infrared (FT-IR) spectrometer and coupling of the hollow waveguide gas sensor module to a supported capillary membrane sampler (SCMS) for continuous liquid-gas extraction. Different hollow waveguides have been characterized in this study for developing an optimized optical configuration. Analysis of industrially relevant compounds has been performed, investigating chlorinated hydrocarbons (CHCs), such as dichloromethane and chloroform, representing highly volatile analytes, and 1,4-dioxane as an example of target compounds with low volatility. The suitability of this spectroscopic IR sensing system for industrial applications is demonstrated under simulated real-world conditions with limits of detection in the ppb (v/v) and ppm (v/v) concentration range for CHCs and 1,4-dioxane, respectively.     

圆锥螺纹塞规测量方法综述

随着现代工业的发展,对圆锥螺纹塞规的加工精度提出了更高的要求,如何提高圆锥螺纹塞规的测量准确度成为必须解决的重要课题.本文以接触式测量和非接触式测量分类方法为例,对比分析了国、内外现有的多种圆锥螺纹塞规基面中径测量方法及研究现状,认为利用CCD作为螺纹几何要素探测器件的视觉检测技术将是未来的发展趋势,随着模式识别、图像处理等相关技术的进步,随着机器视觉技术自身的成熟和发展,视觉检测技术将得到更为广泛的应用.     

冲击混响法溶洞探测初步试验

提供一种区别于通常地矿应用的测声时差的新的溶洞声学测试方法一冲击混响法。通过有无溶洞两个模型的声学试验,对测量数据进行时域分析和时频分析,得到混响衰减系数和混响持续时间两个参数,结果表明：两个模型的混响衰减系数和混响持续时间都存在明显差异,空心模型的混响衰减系数较实心模型小．而混响持续时间则比实心模型大。因而为方便快捷地判断有无溶洞的冲击混响法提供了试验依据。     

丁腈橡胶中空纤维阻尼新材料的制备及性能

针对丁腈橡胶(NBR)黏度过大和相转化时间较长难于纺制中空纤维的问题, 采用先与聚氯乙烯(PVC)共混改性再用干-湿相转化的方法制备出轻质、低耗材的丁腈橡胶中空纤维阻尼新材料, 探讨了NBR与PVC质量比和共混聚合物质量分数对NBR中空纤维阻尼及力学性能的影响。结果表明: 中空纤维结构阻尼性能明显优于对应的平板膜结构; 调整NBR与PVC质量比和共混聚合物质量分数可优化NBR中空纤维的拉伸性能及阻尼性能; 可通过提高NBR与PVC质量比使NBR中空纤维阻尼材料的损耗因子峰值所对应的温度向低温方向偏移。共混聚合物质量分数为25%, NBR与PVC质量比为80∶20时, NBR中空纤维阻尼损耗因子最大, 达到0.78。      

再生聚酯中空纤维基吸声材料的制备与性能

随着环境污染问题的不断加剧,瓶片基再生聚酯纤维的开发和应用具有重要意义。本文以再生聚酯中空纤维和皮芯型热粘合纤维为原料,通过热风固结成型制备具有多尺度微孔的吸声材料,表征了聚酯中空纤维的结构与性能,此外采用驻波管法研究了中空纤维的线密度与吸声效果的关系,并提出了“多级”吸声理论。结果表明,线密度为10 D的中空纤维具有最大的中空度,最好的韧性,最优的吸声效果;吸声系数和降噪系数随厚度的增加线性增加,当厚度为2 cm时,降噪系数(NRC)大于0.5,有望成为理想的吸声材料。     

Hollow fibers for delivery of harmonic pulses of Q-switched Nd:YAG lasers

Flexible hollow fibers for delivery of the second, third, and fourth harmonic pulses of Q-switched Nd:YAG lasers are introduced. For the doubled (532-nm) wavelength, we fabricated a hollow fiber with an internal metal and polymer film by using a silver-mirror plating and a liquid-phase-coating method. For tripled (355-nm) and quadrupled (266-nm) Nd:YAG in the ultraviolet region, we fabricated aluminum hollow fibers with or without an internal polymer layer by using the metal-organic chemical-vapor deposition method. Both types of fiber show high stability for the transmission of high-peak power laser pulses with low transmission losses.     

Measurement method for profiling the residual stress of an optical fiber: detailed analysis of off-focusing and beam-deflection effects

The effects of off-focusing and beam deflection on polarimetric stress measurements of optical fibers are investigated. A simple method for reducing the distortion of the phase retardation caused by unwanted beam deflections in residual stress measurement is introduced. The method is examined numerically by ray-tracing techniques and experimentally by use of hollow silica fibers into which various index-matching liquids have been inserted. An autofocusing technique is introduced. The error in stress measurement reproducibility was determined to be less than 4%. We tested the absolute error in measured stress by applying incremental external tension and determined that it is less than 0.464 MPa.     

Determination of molecular orientation of uniaxially stretched polyamide fibers by polarized infrared spectroscopy: comparison of X-ray diffraction and birefringence methods

Polarized infrared (IR) spectroscopy has been used to determine the crystalline and amorphous orientation of polyamide fibers. The transition moment angle of the band at 936 cm-1 of PA66 was determined to be 48 degrees using IR spectroscopy and birefringence measurement. The crystalline orientation of PA66 fibers was estimated from the band at 936 cm-1 while the amorphous orientation of PA66 fibers was obtained by an indirect method. The alpha crystalline orientation of PA6 has been obtained using the band at 930 cm-1 and the amorphous orientation of PA6 has been determined using the band at 1124 cm-1. Crystalline orientation increased rapidly at low draw ratios (DR<3) and increased slowly at higher draw ratios (DR>3) for both PA66 and PA6 fibers, while the amorphous orientation increased slowly throughout the whole extension range for PA66 fibers. A good correlation was found between the crystalline orientation values obtained by infrared spectroscopy and other methods such as X-ray diffraction for PA66 and PA6 fibers. On the basis of this observation, it has been concluded that polarized infrared spectroscopy can be used reliably to measure the orientation of polyamide fibers without combining with other techniques.