套管辅助法测量异型预制棒折射率分布

基于光束扫描法的光纤预制棒折射率测试仪主要适用于直径和长度在一定范围内的圆柱形样品折射率分布的测试。提出一种套管辅助法可实现更短长度、更细直径和变直径样品的折射率测试。该方法将待测样品居中放置于一个尺寸符合测试要求的圆柱形套管内,并在套管内注入折射率匹配油,使其没过待测样品后按常规步骤进行测试。对比实验结果表明,套管辅助法与直接测量法的偏差与仪器的测量误差相当。采用套管法,获得了预制棒拉丝终止后变径区不同位置折射率的径向分布,可为拉丝过程的研究提供参考。     

用光纤测量液体的折射率

本文提出了用光纤测量液体折射率的方法。测量值的范围不受限制，弥补了阿贝折射仪的不足之处。并可使学生对光纤有所了解。     

含负折射率缺陷的光量子阱的透射特性及理论模拟

利用转移矩阵方法对含负折射率缺陷的一维光子晶体量子阱结构的透射特性进行了研究。结果表明,当缺陷为偶数个时,结构透射谱中有两个透射峰;当缺陷为奇数个时,透射谱中只有中心处一个透射峰,且随着缺陷层数的增加,该处峰的品质因子逐渐提高。因电磁波在缺陷处的强烈局域,所以阱中局域态的透射率对缺陷的折射率有很强的依赖作用。通过控制入射光的强度可使缺陷的折射率发生微小的改变,进而使局域态的透射率发生明显改变,这样就可制作高效光开关。     

用光纤杨氏干涉测量液体的折射率

介绍一种用光纤扬氏干涉测量液体折射率方法。测量值的范围不受限制,弥补了阿贝折射仪的不足。方法简单、直观,测量量少,并可使学生对光纤有所了解。     

Dosimetry techniques

The formation and annealing of defects in ion implanted silicon dioxide layers and in connection with them the refractive index change are of high interest for the production of electronic and integrated optical devices.

Several studies have shown that the ion implantation in fused silica leads to a compaction of the material and in consequence to an increasing of the refractive index.^1–6 On the other hand the defect formation in crystalline quartz is connected with a decreasing of the refractive index up to nearly the same value for ion implanted quartz and fused silica layers in the high dose region.^1,5 On the base of this effects optical waveguides had been produced by ion implantation in both material.^2,7–12 However, the nature of the mechanisms responsible for the defect formation and for the changes of the optical properties are not well understood.

This paper reports on the ion dose and annealing temperature dependence of several defects in connection with the refractive index change.     

Optical refractometer based on an asymmetrical twin-core fiber Michelson interferometer

We report and demonstrate an optical refractometer based on a compact fiber Michelson interferometer. The Michelson interferometer is composed of an asymmetrical twin-core fiber containing a central core and a side core. By chemically etching a segment of the twin-core fiber until the side core is exposed, the effective index of the side core in the etched region is sensitive to the environmental refractive index, which leads to a shift of the transmission spectrum of the Michelson interferometer. The experimental results show that such a device has a refractive index resolution of more than 800 nm/refractive index unit in the range of 1.34-1.37.     

高精度V棱镜折射仪光机结构设计

针对传统V棱镜折射仪采用光学度盘,目视对准方式无法满足现代光学玻璃生产线以及高精度折射率测量的需求。提出一种新型的高精度基于CCD 机器视觉对准的V棱镜折射仪的总体设计方案,并对准直光管、传动机构、锁紧和微调机构以及轴角编码测角机构等主要组成部分进行了光机结构设计。在考虑空气折射率影响因素的修正公式的基础上,分析了仪器的检测误差。实验结果表明:其折射率检测精度可达 310-6,满足了高精度V棱镜折射仪的技术指标要求。     

Monitoring some liquid cladding layer properties using LED beam transmittance coefficients through the fiber itself

We report work on the adaptation of a conventional optical fiber assembly to monitor the properties of liquid. An LED¹ was used in conjunction with a home-made fiber cell fitted with glass fiber rods to monitor some of the physical properties of liquid samples. The technique discriminates between different liquids using their light transmittance ability as cladding layer to the glass fiber. Discrimination between liquids according to their transmission coefficients is partly dependant on refractive index of liquids; therefore, samples were also tested with a refractometer for comparison. Results show that the technique is superior to the refractometer in distinguishing between liquids of different indexes.     

All-fiber multimode-interference-based refractometer sensor: proposal and design

A novel all-fiber refractometer sensor is proposed, which is based on multimode interference in the multimode fiber core section sandwiched between two single-mode fibers. A wide-angle beam propagation method in the cylindrical coordinate is employed as the modeling tool for simulation and design of the proposed refractometer sensor. The design for a refractometer is presented that shows that the refractometer would have an estimated resolution of 5.4 x 10(-5) for refractive indices from 1.33 to 1.45 and of 3.3 x 10(-5) for refractive indices from 1.38 to 1.45 through the choice of an appropriate length of the multimode fiber core section.     

A true fiber optic refractometer

The best instrument to measure the refractive index of liquids is the Abbe refractometer which can only provide accuracies of the order of 10⁻⁵ at visible wavelengths and 10⁻⁴ in the near infrared. Here we present a technique by which the exact wavelength positions in the near infrared frequency comb of a tilted grating inscribed in the core of an optical fiber can be used to measure the absolute value of the refractive index of a liquid in which the fiber is inserted, with an accuracy of ±5×10⁻⁵. This is in contrast to typical fiber optic‐based “refractometry” where only refractive index variations can be measured accurately, hence the appellation of “true” fiber optic refractometer here. In addition to the increased accuracy, the fiber refractometer proposed here offers the additional advantages associated with in situ measurements. The performance of this refractometer is demonstrated by measurements in water from room temperature down to near freezing at wavelengths in the 1550 nm window.

     

Optical fiber refractometers based on indium tin oxide coatings fabricated by sputtering

This Letter presents the fabrication of optical fiber refractometers based on indium tin oxide (ITO) coatings deposited by sputtering with response in the visible region. ITO thin films have been sputtered by means of a rotating mechanism that enables the fabrication of smooth and homogeneous coatings onto the optical fiber core. The ITO coating acts as a resonance supporting layer. This permits us to couple light from the waveguide to the ITO-coating/external medium region at specific wavelength ranges. The device is sensitive to external medium refractive index, which allows its utilization as a refractometer. The sensitivity is dependent on the coating thickness, ranging from 523.21 to 1221 nm/refractive index unit in the explored sensors. The sensor development process is time effective compared to other techniques such as dip coating or layer-by-layer self-assembly, which is interesting in terms of mass production.     

Modal coupling in fiber tapers decorated with metallic surface gratings

An interference-based scheme for fabricating periodic metal gratings on one side of the uniform waist of optical fiber tapers has been developed. Optical characterization of a 5 mm long, 511 nm period gold grating fiber taper with a 10 microm diameter reveals backward coupling to both guided and radiation modes that is explained by using an analytical mode-coupling analysis. A refractometer based on this grating taper has a high and constant sensitivity over a large refractive index operating range of 1 to 1.41.     

Optical characterization and composition of abdominal wall muscle from rat

Complete optical characterization of biological tissue is desirable to develop clinical methods using optical technologies. Particularly, to develop optical clearing methods in biological tissues, it is necessary to know the composition of the tissue, the percentage of each constituent and corresponding refractive indexes. To obtain such information for rat muscle, we used a simple method to characterize tissue constituents for both content percentage and refractive index. The study consisted on measuring mass with a precision weighting scale and the refractive index with an Abbe refractometer during tissue dehydration. With the collected data, we used a theoretical model to calculate the refractive index and percentage for both interstitial fluid and solid part of the rat muscle. The results obtained are in good agreement with data published by other authors, and were considered of vital information for the optical clearing studies that we planned to perform.     

Temperature-calibrated fiber-optic refractometer based on acompact FBG-SMS structure

A novel all-fiber temperature-calibrated refractometer based on a compact fiber Bragg grating(FBG) single-multi-single(SMS)structure is proposed and experimentally demonstrated.The sensor head is composed of a FBG combined with a SMS structure,in which the middle multimode fiber(MMF)section is etched by a time-controlled hydrofluoric.The transmission dip of SMS is extremely sensitive to ambient refractive index(RI)variation,whereas the upstream FBG provides the necessary temperature information for RI calibration.All aforementioned functions are performed via a compact FBG-SMS structure not longer than 25 mm.The proposed sensing device provides a linear RI sensitivity over water or waterbased solutions(RI values near 1.33 at optical wavelengths for most biological and many environmental applications),and has temperature-calibration capability.Hence,the said refractometer is a good candidate for sensing in chemical and biological applications.     

刚性光纤元器件芯,皮玻璃的相互散

通过扫描电子显微镜观察到刚性光纤元器件芯、皮玻璃之间有扩散层,用干涉仪测量了扩散层的折射率范围。本文从玻璃网络结构观点解释了这一扩散机理,并就刚性光纤元器件芯、皮玻璃配方设计中如何使离子扩散减到最小程度提出了可行性措施。     

Chromatic dispersion behavior of Si-NC-Er doped optical fiber

The chromatic dispersion for conventional and Er-doped fibers using the refractive index approximation is examined. A first, analytical method for investigation of dispersion in step index triple clad optical fiber is used. To design of zero-dispersion shifted fiber for optical communication purpose manipulation of the refractive index and radius of the core are considered. We show that in presence of the Si-NC-Er ions, zero-dispersion wavelength is displaced and the dispersion quantity is increased. In this work, we try to optimize system parameters to obtain minimum dispersion and dispersion shifted fiber with control of the doping levels of Er ions and Si-NC as well as doping profiles. For especial case, we assumed the Gaussian inhomogeneous core refractive index for zero-dispersion wavelength and dispersion managements.     

含双负缺陷的一维光子晶体耦合腔的杂质带特性

利用转移矩阵方法研究了含双负缺陷的一维光子晶体耦合腔的透射谱.计算结果表明，如果改变缺陷的折射率，缺陷模之间的耦合作用将发生改变，使得能隙中的杂质带也随之改变.若这个折射率取适当值，则可以在禁带中同时出现几个尖锐的透射峰和较宽的通带，这种结构可同时用于多通道窄带滤波和宽带滤波. 关键词： 光子晶体 缺陷模 杂质带 滤波     

锗在吸收边附近的压力—折射率系数

目前半导体锗在吸收边附近(1550 nm)的压力-折射率系数在实验和理论上并未研究清楚.本文通过测量在不同压力下镀在光纤端面的高结晶度锗薄膜的反射率,来计算得到锗在吸收边附近的压力-折射率系数.本文的实验结果显示,锗在吸收边附近出现反常色散现象,即折射率随能量变化呈正相关,并且其压力-折射率系数出现反常,为正值,这是由于多晶结构中的激子吸收所引起.通过引入描述激子色散的临界点模型,得到锗在吸收边附近的反常色散范围和压力-折射率系数呈正值的范围.本文的结果将有助于基于锗薄膜的通信C波段光学器件的研究.     

Photosensitivity and photoluminescence of Sn/Yb codoped silica optical fiber preform

Sn/Yb codoped silica optical fiber preform is prepared by the modified chemical vapor deposition （MCVD） followed by the solution-doping method. Ultraviolet （UV） optical absorption, photoluminescence （PL） spectra under 978-nm laser diode （LD） pumping, and refractive index change after exposure to 266-nm laser pulses are obtained. There is only a little change in the PL spectra while a positive refractive index change up to 2×10^-4 is observed after 30-min exposure to 266-nm laser pulses. The results show that both of the peculiar photosensitivity of Smdoped silica and the gain property of Yb-doped silica fiber are preserved in the Sn/Yb codoped silica optical fiber preform. The experimental data suggest that the photosensitivity of the fiber preform under high energy density laser irradiation should be mainly due to the bond-breaking of oxygen deficient defects, while under relatively low energy density laser irradiation, the refractive index change probably originates from the photoconversion of optically active defects.     

一维光子晶体掺杂缺陷模研究

用特征矩阵法计算了光波在包含多种掺杂缺陷的一维光子晶体中的传播规律,与不包含缺陷的结构相比较,在禁带中形成缺陷模。缺陷模的位置、数目和强度不仅和缺陷的产生方式有关,还和缺陷位置处的光学厚度及折射率的变化有关。当掺杂缺陷的位置呈等间距时,相应缺陷模也呈等间距排列。随着掺杂缺陷光学厚度的变化,缺陷模的位置、数目也随之变化。保持掺杂缺陷光学厚度不变,掺杂缺陷折射率的变化将会引起缺陷模强度的变化,并存在一个最大值。缺陷模的出现一般使带隙加宽,尤其是掺杂介质的折射率与周期介质的折射率差别较大时更加明显。掺杂空气介质时可使缺陷模的透射率近似为1。