Flexible Graphene‐, Graphene‐Oxide‐, and Carbon‐Nanotube‐Based Supercapacitors and Batteries

Flexible energy‐storage devices increasingly attract attention owing to their advantages of providing lightweight, portable, wearable, or implantable capabilities. Many efforts are made to explore the structures and fabrication processes of flexible energy‐storage devices for commercialization. Here, the most recent advances in flexible energy‐storage devices based on graphene, graphene oxide (GO), and carbon nanotubes (CNTs), are described, including flexible supercapacitors and batteries. First, properties, synthesis methods, and possible applications of those carbon‐based materials are described. Then, the development of carbon‐nanotube‐based flexible supercapacitors, graphene/graphene‐oxide‐based flexible supercapacitors, and graphene‐ and carbon‐nanotube‐based flexible battery electrodes are discussed. Finally, the future trends and perspectives in the development of flexible energy‐storage devices are highlighted.     

Potassium‐Sodium‐Niobate‐Based Thin Films: Lead Free for Micro‐Piezoelectrics

Extensive research and great progress of (K,Na)NbO₃ (KNN)‐based lead‐free piezoelectric films have been driven by the current legislation and the requirement for sustainable development of society and environment in the applications of microelectromechanical systems. A comprehensive discussion of the recent achievement in KNN‐based films is presented herein. First, the available synthetic techniques, chemical modification, the ferroelectric and piezoelectric properties of KNN‐based films are reviewed, followed by an introduction of the crystal structures and electrical properties of KNN‐based epitaxial films in comparison with the bulk ceramics. Finally, the applications of KNN‐based films for the sensors, the energy harvesters, and energy storage devices are addressed, and current challenges and prospects for future work are discussed.     

Metal Nanoclusters–Based Ratiometric Fluorescent Probes from Design to Sensing Applications

Ratiometric fluorescent probes have many advantages including improved sensitivity, high reliability and accuracy, visualization sensing, etc. Herein, the development of metal nanoclusters (NCs)‐based ratiometric fluorescent probes in the recent years is summarized. NCs, an emerging new class of fluorescent nanomaterials, have demonstrated excellent optical properties, good biocompatibility, great aqueous solubility, low cost, and simple synthesis, and NCs‐based ratiometric fluorescent probes have attracted much attention. In this progress report, the preparation and properties of NCs and the design of ratiometric fluorescent probes are summarized. Sensing of a broad range of analytes including cations, gas, small molecules, macromolecules, temperature, and pH is discussed. In addition, the challenges and future directions for NCs‐based ratiometric fluorescent probes are also presented.     

Three‐dimensional optical laser lithography beyond the diffraction limit

Direct laser writing has become a versatile and routine tool for the mask‐free fabrication of polymer structures with lateral linewidths down to less than 100 nm. In contrast to its planar counterpart, electron‐beam lithography, direct laser writing also allows for the making of three‐dimensional structures. However, its spatial resolution has been restricted by diffraction. Clearly, linewidths and resolutions on the scale of few tens of nanometers and below are highly desirable for various applications in nanotechnology. In visible‐light far‐field fluorescence microscopy, the concept of stimulated emission depletion (STED) introduced in 1994 has led to spectacular record resolutions down to 5.6 nm in 2009. This review addresses approaches aiming at translating this success in optical microscopy to optical lithography. After explaining basic principles and limitations, possible depletion mechanisms and recent lithography experiments by various groups are summarized. Today, Abbe's diffraction barrier as well as the generalized two‐photon Sparrow criterion have been broken in far‐field optical lithography. For further future progress in resolution, the development of novel tailored photoresists in combination with attractive laser sources is of utmost importance.     

Second harmonic generation microscopy: principles and applications to disease diagnosis

In this review, the authors discuss the underlying principles of SHG and specific factors that affect the generation properties and describe the essential components of a SHG instrument. In addition, results on the recent progress and impact SHG microscopy has made in different areas of biology and medicine are presented. In particular, the authors focus on disease diagnosis and basic research associated with connected tissues, musculo‐skeletal disorders, and epithelial cancers. The presentation is concluded by offering a perspective on the future technical development of SHG microscopy and additional forefronts to be addressed.     

Coherent anti‐Stokes Raman scattering in Raman lasers and Raman wavelength converters

In this paper recent research progress on the use of Coherent Anti‐Stokes Raman Scattering (CARS) in Raman lasers and Raman wavelength converters is reviewed. The latest insights in the physical nature and behavior of CARS are addressed, and the recent performance breakthroughs in CARS‐based Raman wavelength conversion are discussed. Based on the new findings regarding the behavior of CARS, a physical explanation for apparent inconsistencies in various experimental observations of Raman wavelength conversion is provided. To conclude it is shown that these recent insights also pave the way to the development of a novel CARS‐based mechanism for reducing the heat dissipation in Raman lasers.     

Laser applications and system considerations in ocular imaging

We review laser applications for primarily in‐vivo ocular imaging techniques, describing their constraints based on biological tissue properties, safety, and the performance of the imaging system. We discuss the need for cost‐effective sources with practical wavelength‐tuning capabilities for spectral studies. Techniques to probe the pathological changes of layers beneath the highly scattering retina and diagnose the onset of various eye diseases are described. The recent development of several optical‐coherence‐tomography‐based systems for functional ocular imaging is reviewed, as well as linear and nonlinear ocular‐imaging techniques performed with ultrafast lasers, emphasizing recent source developments and methods to enhance imaging contrast.     

Growth and properties of InGaAs nanowires on silicon

Free‐standing ternary InGaAs nanowires (NW) are at the core of intense investigations due to their integration capabilities on silicon (Si) for next‐generation photovoltaics, integrated photonics, tunneling devices, and high‐performance gate all‐round III–V/Si NW transistors. In this review, recent progress on the growth, structural, optical and electrical properties of InGaAs NWs on Si substrate is highlighted. Particular focus is on a comparison between conventional catalyst‐assisted and catalyst‐free growth methods as well as self‐assembled versus site‐selectively grown NW arrays. It will be shown that catalyst‐free, high‐periodicity NW arrays with extremely high compositional uniformity are mandatory to allow un‐ambiguous structure–property correlation measurements. Here, interesting insights into the electronic/optical properties of wurtzite, zincblende and mixed crystal phases of InGaAs will be highlighted based on recent photoluminescence spectroscopy data. Finally, the InGaAs NW‐on‐Si system is also discussed in the realms of heterojunction properties, providing a promising system for steep‐slope tunneling field effect transistors in future low‐power post‐CMOS intergrated microelectronics and broad‐band photoabsorption and detec‐tion devices. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

High Average Power Near‐Infrared Few‐Cycle Lasers

Ultra‐short laser pulses with only a few optical cycles duration have gained increasing importance during the recent decade and are currently employed in many laboratories worldwide. In addition, modern laser technology nowadays can provide few‐cycle pulses at very high average power which advances established studies and opens exciting novel research opportunities. In this paper, the two complementary approaches for providing few‐cycle pulses at high average power, namely optical parametric amplification and nonlinear pulse compression, are reviewed and compared. In addition, their limitations and future scaling potential are discussed. Furthermore, selected applications particularly taking advantage of the high average power and high repetition rate are presented.     

Nonlinear optical fiber based high resolution all‐optical waveform sampling

When there is a need to accurately characterize optical waveforms and, it is not surprising that some of the best, albeit only recently established, techniques to do this rely on all‐optical phenomena. Some basic reasons why all‐optical sampling holds great promise as a very useful tool well into the foreseeable future are that there are no ringing phenomena with associated waveform distortion as in electronic sampling due to impedance mismatch, and that the time resolution can be made extremely high (⩽ 1 ps) while yet also offering high sensitivity for e.g. eye diagram (a superposition of all ‘1’ and ‘0’ in a data sequence that is widely used in telecommunications testing) and statistical analysis. In this paper, we review recent developments in optical fiber‐based sampling of optical waveforms. In particular, we describe the state‐of‐the‐art in terms of the various performance measures as well as their trade‐offs.     

纳米结构中的量子问题

文章讨论了纳米器件发展方向和近期的研究成果，指出是子效应和纳米结构是将来的纳米器件的两大基础，以碳纳米管和各种电极组成的纳米结构为代表，论述了不同的量子效应及其在纳米器件中的可能应用。     

电磁超表面在微波和太赫兹波段雷达散射截面缩减中的应用研究进展

电磁超表面由于其独特的电磁特性为调控电磁波提供了有力工具,合适地设计成编码、随机、相位不连续、完美吸收器等超表面,就能够控制电磁波的散射以及反射特性,实现雷达散射截面的缩减。本文综述了不同的电磁超表面利用漫反射或者吸收等特性实现在微波和太赫兹波段雷达散射截面缩减中的应用。分析表明,编码超表面由不同的数字单元组成,其反射相位差在很宽的频段范围内满足恒定的关系,设计特殊的单元序列使入射的电磁波产生非定向散射,更高bit编码超表面更容易灵活调控电磁波;随机超表面通过调节阵元的尺寸实现宽带移相从而将金属目标特征性强的反射峰打散成一个无规律、杂乱的波,产生漫反射;不连续超表面由于相位不连续可使电磁波发生漫反射或者异常反射;吸收器通过合理设计结构尺寸实现吸收电磁波能量来减小反射。因此电磁超表面在雷达隐身、宽带通讯、成像等方面具有重要的应用前景。最后对电磁超表面在雷达散射截面缩减中应用的发展趋势进行了初步探讨,未来将向着宽带、柔性、大角度等方面发展。     

全光非线性光孤子通信系统技术

近年来光孤子通信技术发展很快,各种新方案不断提出,各种系统设计与试验系统技术取得了重大突破,使光孤子通信向衫化迈进一大步,文章综述了光孤子通信技术的最新进展,分析了光孤子通信技术的发展趋势。     

All‐optical virtual private network in passive optical networks

We review recent progress on all‐optical virtual‐private‐network (VPN) schemes in passive optical networks (PONs). PON is a promising candidate in future access areas to provide broadband services with low cost. With all‐optical virtual private network (VPN) function, PON can support efficient internetworking among end users with dedicated optical channels, thus enabling guaranteed bandwidth and enhanced security at the physical layer. Here, we discuss and compare existing schemes of all‐optical VPNs in time‐division‐multiplexed (TDM) PONs, and also recently proposed schemes for deployment in wavelength‐division‐multiplexed (WDM) PONs and two‐stage TDM/WDM PONs.     

Janus Particles: Metallic Janus and Patchy Particles (Part. Part. Syst. Charact. 1/2013)

The concepts of Janus and patchy particles are relatively new in nanoscience. Much effort has been made during recent years to devise and fabricate asymmetric particles with multiple compositions and functionalities due to their interesting properties and potential applications in a variety of fields such as catalysis, optical imaging, or drug delivery. Here, recent advances in the field of Janus particles are highlighted, focusing on nanoparticles comprising (at least) one metallic component, which is responsible for the most interesting properties of the particles. First, the main synthetic approaches are summarized, i.e., phase separation, masking, and self‐assembly techniques, and then the special properties, applications, and future prospects of metallic Janus particles are described.     

The role of virtual photons in nanoscale photonics

The fundamental theory of processes and properties associated with nanoscale photonics should properly account for the quantum nature of both the matter and the radiation field. A familiar example is the Casimir force, whose significant role in nanoelectromechanical systems is widely recognised; the correct representation invokes the creation of short‐lived virtual photons from the vacuum. In fact, there is an extensive range of nanophotonic interactions in which virtual photon exchange plays a vital role, mediating the coupling between particles. This review surveys recent theory and applications, also exhibiting novel insights into key electrodynamic mechanisms. Examples are numerous and include: laser‐induced inter‐particle forces known as optical binding; non‐parametric frequency‐conversion processes especially in rare‐earth doped materials; light‐harvesting polymer materials that involve electronic energy transfer between their constituent chromophores. An assessment of these and the latest prospective applications concludes with a view on future directions of research.     

Cross‐Linked Proteins with Gold Nanoclusters: A Dual‐Purpose pH‐Responsive Material for Controllable Cell Imaging and Antibiotic Delivery

This report describes the development of a facile method for the synthesis of cross‐linked proteins with gold nanoclusters (CP‐GNC). The synthesis reaction is completed within 15 min at 97 °C. The synthesized CP‐GNC are characterized by using UV–vis absorption, fluorescence, X‐ray photoelectron spectroscopy, and transmission electron microscopy. CP‐GNC are approximately 100 nm in diameter and 700 nm in length, whereas AuNCs within the nanorods are approximately 6 nm in size. These materials are highly fluorescent with quantum yield of 7.2% and can be absorbed onto and release from bacterial cells in a pH‐dependent and reversible manner. The recent data show that CP‐GNC can be a useful, new tool with potential applications in fluorescent cell imaging and antibiotic targeting.