Erbium‐doped integrated waveguide amplifiers and lasers

Erbium‐doped fiber devices have been extraordinarily successful due to their broad optical gain around 1.5–1.6 µm. Er‐doped fiber amplifiers enable efficient, stable amplification of high‐speed, wavelength‐division‐multiplexed signals, thus continue to dominate as part of the backbone of longhaul telecommunications networks. At the same time, Er‐doped fiber lasers see many applications in telecommunications as well as in biomedical and sensing environments. Over the last 20 years significant efforts have been made to bring these advantages to the chip level. Device integration decreases the overall size and cost and potentially allows for the combination of many functions on a single tiny chip. Besides technological issues connected to the shorter device lengths and correspondingly higher Er concentrations required for high gain, the choice of appropriate host material as well as many design issues come into play in such devices. In this contribution the important developments in the field of Er‐doped integrated waveguide amplifiers and lasers are reviewed and current and future potential applications are explored. The vision of integrating such Er‐doped gain devices with other, passive materials platforms, such as silicon photonics, is discussed.     

光纤传感阵列用于智能复合材料状态监测的研究

以光纤智能材料与结构中的损伤估计为目的,提出了一种新颖的、利用多模光纤缠绕尼龙筋式的传感器,由这种传感器组成的传感阵列可以对智能材料与结构的受力、应变等参量进行检测,并采用ＯＴＤＲ 技术实时处理其输出的并行分布式传感信号,给出了测试数据、识别结果。在复合材料构件上的初步实验表明此系统能够对结构的状态进行在线监测和估计,在航空航天、船舶工业和土木建筑等领域有着潜在的实用价值。     

利用光纤光栅实现力学量二维实时感测的研究

将一根光纤上写入两个不同波长的布位格光栅，沿矩形悬臂梁的中性而与表面的交线粘贴于靠近固定端两个相邻侧面，利用不纤光栅波长绝对编码的特性，实现了应力（或应变）与位移的二维实时传感测量。理论分析和实验结果证明，通过监测粘贴梁上的两个光纤光栅波长变化的大小和指向，能够实时感测应力、位移等力学量的大小和方向。在与梁轴垂直的方向上，获得应力实验灵敏度分别为5．32nm/N和3．21nm/N，位移实验灵敏度分别为0．30nm/mm和0．48nm/mm。     

基于LP21模式的光纤弯曲传感器

设计并研制了一种基于LP21模式的新型光纤弯曲传感器。该传感器通过检测敷设于弹性基片上的光纤所传输的LP21模式光斑图像的旋转,实现对弯曲值的高精度测量。运用光纤耦合模理论和弹光效应求解LP21的模方程,证明该模式具有弯曲无关和扭转线性的特性,并检验了光纤弯曲传感器对不同结构参数和环境温度下的性能。实验结果与理论分析相吻合,证实该传感器具有较大的线性动态范围,温度稳定性高,且能辨识弯曲方向。     

原子尺度金属纳米线的结构和性质

当物质尺度减少到几层原子时，形成超细的纳米结、纳米线、或者纳米团簇，原有凝聚态物质的结构和物理性质将不再保持，而呈现出许多令人惊奇的奇异特性。本文重点讨论直径大约3nm以下，具有足够长度的、原子结构往往不同于体材料的准一维金属纳米结构，我们称之为原子尺度金属纳米线或超细金属纳米线（也称为金属原子线）。近年来实验上已经制备和表征出在超高真空中悬挂在两个顶针尖端的Au、Pt、Cu等金属纳米线和纳米管，金属线直径达到1nm以下而长度为6nm以上。通过高分辩电子显微镜观察，它们是同轴圆管（或壳）组成的、类似纳米碳管的单壳或多壳结构，管由绕着线轴的螺旋原子绳构成。理论工作围绕这种新奇结构形态的形成机制、奇异的物理性质和可能的应用前景而同时展开。这是一个崭新的纳米世界，无论是对基础的低维物理还是未来分子电子设备的应用，都将产生深远的影响，有许多奇妙的现象正等待人们去发现。本文将对最近几年原子尺度金属纳米线研究工作的主要进展和发展趋势作一个概述，并重点介绍本组有关的具有螺旋结构的纳米线的各类新奇结构和物理性质。     

原子尺度金属纳米线的结构和性质

当物质尺度减少到几层原子时,形成超细的纳米结、纳米线、或者纳米团簇,原有凝聚态物质的结构和物理性质将不再保持,而呈现出许多令人惊奇的奇异特性。本文重点讨论直径大约3 nm以下,具有足够长度的、原子结构往往不同于体材料的准一维金属纳米结构,我们称之为原子尺度金属纳米线或超细金属纳米线(也称为金属原子线)。近年来实验上已经制备和表征出在超高真空中悬挂在两个顶针尖端的Au、Pt、Cu等金属纳米线和纳米管,金属线直径达到1 nm以下而长度为6 nm以上。通过高分辩电子显微镜观察,它们是同轴圆管(或壳)组成的、类似纳米碳管的单壳或多壳结构,管由绕着线轴的螺旋原子绳构成。理论工作围绕这种新奇结构形态的形成机制、奇异的物理性质和可能的应用前景而同时展开。这是一个崭新的纳米世界,无论是对基础的低维物理还是未来分子电子设备的应用,都将产生深远的影响,有许多奇妙的现象正等待人们去发现。本文将对最近几年原子尺度金属纳米线研究工作的主要进展和发展趋势作一个概述,并重点介绍本组有关的具有螺旋结构的纳米线的各类新奇结构和物理性质。     

增益导引-折射率反导引大模场光纤激光器抽运技术研究进展

介绍了一种新型增益导引-折射率反导引大模场光纤的结构、基本理论以及其在光纤激光器领域的重要应用. 在综合分析了不同抽运条件下的激光输出特性以及光纤的热效应特征后, 得出侧面抽运是增益导引-折射率反导引大模场光纤的最佳抽运方案的结论; 重点介绍了增益导引-折射率反导引大模场光纤侧面抽运的理论模拟以及基于V形槽技术的侧面抽运实验研究过程, 为相关领域的实验研究提供了参考; 最后分析了实验结果与理论差距较大的原因, 并提出了改进的方向.     

Influence of mode competition on beam quality of fiber amplifier

Theoretical and experimental studies of the influence of the mode competition on the output beam quality of fiber amplifiers are presented. Rate equations and modal decomposition method are used in the theoretical model. In the experiment, the output beam-quality factor of a fiber amplifier, which is based on a Yb-doped double-clad large mode area fiber as a function of the seed beam quality and the pump power of the amplifier, is measured. The experimental results are consistent with the theoretical analysis.     

光纤光栅传感器的应用

在光纤传感领域，光纤光栅传感技术是十多年来发展最为迅速的技术之一，传感系统本身和应用领域均有了很大发展．文章介绍了光纤光栅的结构、性能以及传感的原理，回顾了光纤光栅传感器在地球动力学、航天器及船舶航运、民用工程结构、电力工业、医学、和化学传感中的应用．     

光纤激光器自混合干涉效应研究

针对光纤激光器自混合干涉传感应用,研究了光纤激光器自混合干涉特性,运用四镜法布里-珀罗腔模型对掺铒线形腔光纤激光器自混合干涉效应进行了理论分析,对不同反馈水平下的自混合干涉信号进行了数值模拟,获得了光反馈条件下光纤激光器输出特性.外腔长度的改变会调制激光器的输出强度,外腔长度变化半个波长,对应一个干涉条纹,弱反馈条件下,由反馈引起的激光器的频率变化可以忽略.设计了基于光纤激光器的自混合干涉实验,实验结果和理论分析相符合.此研究结果为进一步开展光纤激光器的自混合干涉传感应用研究奠定了理论与实验基础.     

A study of multi-trapping of tapered-tip single fiber optical tweezers

We develop a pair of tapered-tip single fiber optical tweezers, and study its multi-trapping characteristic. The finite difference time domain method is employed to simulate the trapping force characteristic of this pair of single fiber optical tweezers, and the results show that the number of trapped particles depends on the refractive index and the size of the particles. The trapping force of this pair of tapered-tip single fiber optical tweezers is calibrated by the experimental method, and the experimental results are consistent with the theoretical calculation results. The multi-trapping capability realized by the tapered-tip single fiber optical tweezers will be practical and useful for applications in biomedical research fields.     

Lessons from nature: biomimetic subwavelength structures for high‐performance optics

In nature, optical structures in the subwavelength range have been evolved over millions of years. For example, in the form of ‘moth‐eye’ structures they show a strong anti‐reflective effect on the compound eyes of night‐active insects and therefore offer a successful protection over predators. In this contribution the advantages and challenges to transfer this natural concept of subwavelength structured optical interfaces to high‐end optical systems are discussed. Here, in comparison to alternative conventional multilayer systems, the bioinspired anti‐reflective structures offer a wide wavelength range and a broad angle dependency. Additionally, adhesion problems are reduced drastically. Simultaneously to the theoretical consideration of the best profile form of the subwavelength structures, appropriate realization technologies have been developed in recent years, where both top‐down and bottom‐up approaches have been investigated. Depending on the choice of the structuring technique, anti‐reflective subwavelength structures are applicable to a wide spectrum of optical elements ranging from micro‐optical components to aspheres for applications in imaging and also illumination setups of high‐end optical instruments.     

MEMS electrodynamic loudspeakers for mobile phones

This paper presents a MEMS structure of electrodynamic loudspeakers dedicated to mobile phone applications. The major goals are to obtain a high electroacoustic conversion efficiency and a high fidelity acoustic quality. The originalities lie in a rigid silicon membrane and in its suspension by a set of silicon beams. The moving coil is a planar copper microcoil electroplated on the silicon membrane whose microstructure was optimized for providing both rigidity and lightness of the mobile part.This paper presents different magnetic structures of the motor for this MEMS loudspeaker. These structures are ironless, only made out of permanent magnets which are bonded on the substrate. They are studied and optimized thanks to analytical formulations of the magnetic field created by the permanent magnets. Results are presented for a deep RIE etched 7.5 mm radius silicon membrane structured with 40 stiffening ribs and on a 30 μm thick microcoil with 35 turns.     

伽马辐照对掺铒光纤性能影响的研究

为了推进掺铒光纤抗辐射性能的研究,全面掌握掺铒光纤性能在辐照条件下的变化规律。基于色心模型对掺铒光纤的辐照作用机理进行了分析,并据此对掺铒光纤在辐照中的性能变化趋势进行了预测推断。然后根据掺铒光纤的工作原理和应用特性,在伽马辐照条件下对两种不同型号(EDF-L-980和MP980)掺铒光纤的980 nm波段损耗谱、1 530 nm波段损耗谱以及发射光谱的特性进行了在线实时监测,并在辐照停止后进行了恢复测量。研究表明,在辐照中两种掺铒光纤的性能变化趋势一致。在损耗谱方面,980 nm波段和1 530 nm波段的损耗随辐照单调增加,980 nm吸收峰与1 530 nm吸收峰处的损耗与辐照剂量呈近似线性关系;在发射光谱方面,发射光谱强度随辐照单调降低,光谱能量向长波方向转移,平均波长和光谱带宽大幅增加,1 530 nm发射峰处的发光强度与辐照剂量也呈近似线性关系。辐照停止后,掺铒光纤体现出了一定的恢复能力,但是各项参数的恢复均不到40%。各项实验结果与理论模型和分析预测匹配良好,证明了辐照对掺铒光纤性能影响理论解释的合理性。     

High‐power random distributed feedback fiber laser: From science to application

A fiber laser based on random distributed feedback has attracted increasing attention in recent years, as it has become an important photonic device and has found wide applications in fiber communications or sensing. In this article, recent advances in high‐power random distributed feedback fiber laser are reviewed, including the theoretical analyses, experimental approaches, discussion on the practical applications and outlook. It is found that a random distributed feedback fiber laser can not only act as an information photonics device, but also has the feasibility for high‐efficiency/high‐power generation, which makes it competitive with conventional high‐power laser sources. In addition, high‐power random distributed feedback fiber laser has been successfully applied for midinfrared lasing, frequency doubling to the visible and high‐quality imaging. It is believed that the high‐power random distributed feedback fiber laser could become a promising light source with simple and economic configurations.

     

激光全息光刻技术在微纳光子结构制备中的应用进展

微纳光子结构研究随着光子学、半导体物理学及微加工技术的发展而逐渐蓬勃开展,并在其结构、理论、制备技术等方面取得了系列进展。受限于目前的微加工技术水平,要成功制备大尺度、高质量的光子材料仍然存在着一定挑战。激光全息光刻技术作为一种简便快捷的微结构制作技术已经发展成为一种经济快速制作大面积微纳超材料及光子晶体模板的重要手段。介绍了激光全息光刻技术的原理,详细阐述了该技术在制作三维面心立方、木堆积结构、金刚石结构光子晶体以及光学周期类准晶、手性超材料、周期性缺陷结构等微纳光子结构中的应用研究进展。激光全息光刻技术成功制作微纳光子结构为光子材料在更多领域的广泛应用提供了基础和方法。     

Tilted fiber Bragg grating sensors

Optical fiber gratings have developed into a mature technology with a wide range of applications in various areas, including physical sensing for temperature, strain, acoustic waves and pressure. All of these applications rely on the perturbation of the period or refractive index of a grating inscribed in the fiber core as a transducing mechanism between a quantity to be measured and the optical spectral response of the fiber grating. This paper presents a relatively recent variant of the fiber grating concept, whereby a small tilt of the grating fringes causes coupling of the optical power from the core mode into a multitude of cladding modes, each with its own wavevector and mode field shape. The main consequence of doing so is that the differential response of the modes can then be used to multiply the sensing modalities available for a single fiber grating and also to increase the sensor resolution by taking advantage of the large amount of data available. In particular, the temperature cross‐sensitivity and power source fluctuation noise inherent in all fiber grating designs can be completely eliminated by referencing all the spectral measurements to the wavelength and power level of the core mode back‐reflection. The mode resonances have a quality factor of 10⁵, and they can be observed in reflection or transmission. A thorough review of experimental and theoretical results will show that tilted fiber Bragg gratings can be used for high resolution refractometry, surface plasmon resonance applications, and multiparameter physical sensing (strain, vibration, curvature, and temperature).     

Optical sensing with photonic crystal fibers

A review of optical fiber sensing demonstrations based on photonic crystal fibers is presented. The text is organized in five main sections: the first three deal with sensing approaches relying on fiber Bragg gratings, long‐period gratings and interferometric structures; the fourth one reports applications of these fibers for gas and liquid sensing; finally, the last section focuses on the exploitation of nonlinear effects in photonic crystal fibers for sensing.     

Fabrication methods of 3D periodic metallic nano/microstructures for photonics applications

Periodic metallic nano/microstructures have received a great a deal of attention in the photonics research community over the last few decades due to their intriguing optical properties. Three‐dimensional metallic nano/microstructures such as metallic photonic crystals, metamaterials, and plasmonic devices possess unique characteristics of tailored thermal radiation, negative refraction and deep subwavelength confinement of light. In this article, the recent progress on the experimental methods for the realisation of three‐dimensional periodic metallic and thin metal film coated dielectric nano/microstructures operating from optical to mid‐infrared frequencies has been reviewed. Advancement of the state‐of‐the‐art nanofabrication methods over the last few decades have led to the development of metallic nano/microstructures of diverse geometries, high resolution features and large scale production. The recent progress in the novel fabrication methods have inspired the development of functional and exciting photonic devices based on periodic metallic nano/microstructures with various applications in photonics including communications, photovoltaics, and biophotonics.