干涉成象光谱技术

介绍典型的干涉成象光谱仪，包括基于Ｍｉｃｈｅｌｓｏｎ干涉仪的动镜扫描型，基于横切分束器的无动镜型和基于Ｆａｂｒｙ－Ｐｅｒｏｔ干涉仪的多光束干涉型等，给出基基本公式并分析其主要特点。     

In‐Situ‐Charakterisierung optischer Mehrschichtsysteme in Großflächen‐ Produktionsanlagen

The paper discusses approaches to the insitu analysis of optical multi‐layer coating stacks such as mirror coatings, AR coatings or lowE layer stacks on large‐area substrates in production environments. The stable production of complex layer systems requires in‐situ analysis systems that are able to provide spectral information and optical performance data, but also yield thickness information for individual layers and thus aide the operating staff in detailed analyzing deviations from the production target stack. Solutions incorporating in‐situ optical reflectance, transmittance and ellipsometry measurements wi^th optical data being collected not only for the completed layer stack, but also at intermediate coating stages, are discussed and the accuracy, robustness and stability of different measurement systems and computation strategies are compared.     

Ge2Sb2Te5‐Based Tunable Perfect Absorber Cavity with Phase Singularity at Visible Frequencies

The metal‐dielectric stacks‐based asymmetric Fabry–Perot (F–P) cavity systems have recently attracted much interest from the scientific community for realizing perfect absorption over the spectral bands from visible to infrared since they possess a lithography‐free design that is cost‐effective and scalable. This study experimentally demonstrates an asymmetric F–P cavity system for achieving tunable wide angle perfect absorption and phase singularity. The proposed system shows tunable multiband perfect absorption in the visible spectral region by incorporating an ultrathin layer of phase change material such as Ge₂Sb₂Te₅ (GST) in the stack. The system shows multi‐narrowband perfect absorption with a maximum of 99.8% at a specific incident angle and polarization state when the GST is in amorphous phase; however, the absorption bands blueshift and broaden after switching to the crystalline phase. More importantly, the proposed scheme shows tunable phase singularity at the reflection‐less point. The obtained tunable perfect absorption and abrupt phase change are solely due to the presence of a highly absorbing ultrathin layer of GST in the stack. Experimental results are validated using an analytical simulation model based on a transfer matrix method. The proposed scheme could find potential applications in active photonic devices such as phase‐sensitive biosensors and absorption filters.     

Triple‐Mode Emissions with Invisible Near‐Infrared After‐Glow from Cr3+‐Doped Zinc Aluminum Germanium Nanoparticles for Advanced Anti‐Counterfeiting Applications

Materials exhibiting persistent luminescence (PersL) have great prospect in optoelectronic and biomedical applications such as optical information storage, bio‐imaging, and so on. Unfortunately, PersL materials with multimode emission properties have been rarely reported, although they are expected to be very desirable in multilevel anti‐counterfeiting and encryption applications. Herein, Cr³⁺‐doped zinc aluminum germanium (ZAG:Cr) nanoparticles exhibiting triple‐mode emissions are designed and demonstrated. Upon exposure to steady 254 nm UV light, the ZAG:Cr nanoparticles yield steady bluish‐white emission. After turning off the UV light, the emission disappears quickly and the mode switches to transient near‐infrared (NIR) PersL emission at predominantly 690 nm. The transient NIR PersL emission which arises from Cr³⁺ is induced by non‐equivalent substitution of Ge⁴⁺. After persisting for 50 min, it can be retriggered by 980 nm photons due to the continuous trap depth distribution of ZAG:Cr between 0.65 and 1.07 eV. Inspired by the triple‐mode emissions from ZAG:Cr, multifunctional luminescent inks composed of ZAG:Cr nanoparticles are prepared, and high‐security labeling and encoding encryption properties are demonstrated. The results indicate that ZAG:Cr nanoparticles have great potential in anti‐counterfeiting and encryption applications, and the strategy and concept described here provide insights into the design of advanced anti‐counterfeiting materials.     

Solid‐State Electrolyte‐Gated Graphene in Optical Modulators

The gate‐tunable wide‐band absorption of graphene makes it suitable for light modulation from terahertz to visible light. The realization of graphene‐based modulators, however, faces challenges connected with graphene's low absorption and the high electric fields necessary to change graphene's optical conductivity. Here, a solid‐state supercapacitor effect with the high‐k dielectric hafnium oxide is demonstrated that allows modulation from the near‐infrared to shorter wavelengths close to the visible spectrum with remarkably low voltages (≈3 V). The electroabsorption modulators are based on a Fabry–Perot‐resonator geometry that allows modulation depths over 30% for free‐space beams.     

Lanthanide‐Doped Core@Multishell Nanoarchitectures: Multimodal Excitable Upconverting/Downshifting Luminescence and High‐Level Anti‐Counterfeiting

The development of luminescent materials with concurrent multimodal emissions is a great challenge to improve security and data storage density. Lanthanide‐doped nanocrystals are particularly appropriate for such applications for their abundant intermediate energy states and distinguishable spectroscopic profiles. However, traditional lanthanide luminescent nanoparticles have a limited capacity for information storage or complexity to shield against counterfeiting. Herein, it is demonstrated that the combination of upconverting and downshifting emissions in a particulate designed lanthanide‐doped core@multishell nanoarchitecture allows the generation of multicolor dual‐modal luminescence over a wide spectral range for complex information storage. Precise control of lanthanide dopants distribution in the core and distinct shells enables simultaneous excitation of 980/808 nm focusing/defocusing laser and 254 nm light and produces complex upconverting emissions from Er, Tm, Eu, and Tb via multiphoton energy transfer processes and downshifting emissions from Eu and Tb via efficient energy transfer from Ce to Eu/Tb in Gd‐assisted lattices. It is experimentally proven that multiple visualized anti‐counterfeit and information encryption with facile decryption and authentication using screen‐printing inks containing the present core@multishell nanocrystals are practically applicable by selecting different excitation modes.     

Broadband,Spectrally Flat,Graphene‐based Terahertz Modulators

Advances in the efficient manipulation of terahertz waves are crucial for the further development of terahertz technology, promising applications in many diverse areas, such as biotechnology and spectroscopy, to name just a few. Due to its exceptional electronic and optical properties, graphene is a good candidate for terahertz electro‐absorption modulators. However, graphene‐based modulators demonstrated to date are limited in bandwidth due to Fabry–Perot oscillations in the modulators’ substrate. Here, a novel method is demonstrated to design electrically controlled graphene‐based modulators that can achieve broadband and spectrally flat modulation of terahertz beams. In our design, a graphene layer is sandwiched between a dielectric and a slightly doped substrate on a metal reflector. It is shown that the spectral dependence of the electric field intensity at the graphene layer can be dramatically modified by optimizing the structural parameters of the device. In this way, the electric field intensity can be spectrally flat and even compensate for the dispersion of the graphene conductivity, resulting in almost invariant absorption in a wide frequency range. Modulation depths up to 76% can be achieved within a fractional operational bandwidth of over 55%. It is expected that our modulator designs will enable the use of terahertz technology in applications requiring broadband operation.     

A Supramolecular Nanocomposite as a Near‐Infrared‐Transmitting Optical Filter for Security and Forensic Applications

Visibly opaque but near‐infrared (NIR)‐transparent materials are an essential component for night‐vision photography, security imaging, and forensic applications. Herein, the development of a novel supramolecular black dye from a diketopyrrolopyrrole (DPP)‐based low‐molecular‐weight organogelator is described. In the solution state, the monomer of DPP–Amide exhibits a deep green color with a broad absorption in the visible region due to firm intramolecular charge transfer from the donor to the acceptor unit. Interestingly, due to the synergistic effect of H‐bonding and π‐stacking, DPP–Amide can form a black organogel in toluene with complete spectral coverage from 300 to 800 nm, and transmits beyond 850 nm. In the gel state, complete visible‐spectrum coverage is achieved due to the simultaneous formation of both H‐ and J‐type aggregates, which is confirmed via absorption studies. To create a free‐standing NIR‐transmitting elastomeric black filter, nanoscopic molecular aggregates of DPP–Amide (0.15 wt%) are embedded into a poly(dimethylsiloxane) matrix. This nanocomposite possesses high NIR transparency with good thermal and photostability for practical applications. Finally, the use of the developed material for NIR photography, security, and forensic‐related applications is demonstrated.     

Large‐Field‐of‐View Wide‐Spectrum Artificial Reflecting Superposition Compound Eyes

In nature, reflecting superposition compound eyes (RSCEs) found in shrimps, lobsters and some other decapods are extraordinary imaging systems with numerous optical features such as minimum chromatic aberration, wide‐angle field of view (FOV), high sensitivity to light and superb acuity to motion. Here, we present life‐sized, large‐FOV, wide‐spectrum artificial RSCEs as optical imaging devices inspired by the unique designs of their natural counterparts. Our devices can form real, clear images based on reflection rather than refraction, hence avoiding chromatic aberration due to dispersion by the optical materials. Compared to imaging at visible wavelengths using conventional refractive lenses of comparable size, our artificial RSCEs demonstrate minimum chromatic aberration, exceptional FOV up to 165° without distortion, modest aberrations and comparable imaging quality without any post‐image processing. Together with an augmenting cruciform pattern surrounding each focused image, our large‐FOV, wide‐spectrum artificial RSCEs possess enhanced motion‐tracking capability ideal for diverse applications in military, security, medical imaging and astronomy.     

A Strategic Approach to Design Multi-Functional RGB Luminescent Security Pigment Based Golden Ink with Myriad Security Features to Curb Counterfeiting of Passport

Authentication and verification of the most important government issued identity proof, i.e. passport has become more complex and challenging in the last few decades due to various innovations in ways of counterfeiting by fraudsters. Here, the aim is to provide more secured ink without altering its golden appearance in visible light. In this panorama, a novel advanced multi-functional luminescent security pigment (MLSP) based golden ink (MLSI) is developed that provides an optical authentication and information encryption features to protect the legitimacy of the passport. The advanced MLSP is derived from the ratiometric combination of different luminescent materials to form a single pigment which emits red (620 nm), green (523 nm) and blue (474 nm), when irradiated via 254, 365 and 980 nm NIR wavelengths, respectively. It also includes magnetic nanoparticles to generate magnetic character recognition feature. The MLSI has been fabricated to examine its printing feasibility and stability over different substrates using the conventional screen-printing technique against harsh chemicals and under different atmospheric conditions. Hence, these advantageous multi-level security features with golden appearance in visible light is a new breakthrough toward curbing the counterfeiting of passport as well as bank cheques, government documents, pharmaceuticals, military equipment, and many more.     

Layer‐by‐Layer Fabrication of Covalently Crosslinked and Reactive Polymer Multilayers Using Azlactone‐Functionalized Copolymers: A Platform for the Design of Functional Biointerfaces

We report a method for modulating the physicochemical properties of surfaces that is based on the reactive layer‐by‐layer fabrication of covalently crosslinked thin films using azlactone‐functionalized copolymers. We demonstrate that copolymers containing different molar ratios of methyl methacrylate (MMA) and 2‐vinyl‐4,4‐dimethylazlactone (VDMA) can be alternately deposited with poly(ethyleneimine) to assemble covalently crosslinked thin films. Characterization using ellipsometry demonstrates that, in general, film growth and thickness decrease as the content of reactive, azlactone functionality in the copolymer used to assemble the film decreases. Reflective infrared spectroscopy experiments demonstrate that films fabricated from MMA:VDMA copolymers contain residual azlactone functionality and that these reactive groups can be exploited to modify film‐coated surfaces. Fabricating films from MMA:VDMA copolymers containing different compositions permitted modulation of the density of reactive groups within the films and, thus, the extent to which the films are functionalized by exposure to small molecule amines. For example, functionalization of MMA:VDMA copolymer films with the small molecule D ‐glucamine resulted in films with water contact angles that varied with the composition of the copolymer used to fabricate the film (e.g., as the azlactone content in the film increased, glucamine‐modified films became more hydrophilic). We demonstrate further that treatment of copolymer‐containing films with glucamine resulted in changes in the numbers of mammalian cells that grow on the surfaces of the films. Our results suggest the basis of methods that could be used to modulate or tune the density of chemical and biological functionality presented on surfaces of interest in a variety of fundamental and applied contexts.     

Random Organic Nanolaser Arrays for Cryptographic Primitives

Next‐generation high‐security cryptography and communication call for nondeterministic generation and efficient authentication of unclonable bit sequences. Physical unclonable functions using inherent randomness in material and device fabrication process have emerged as promising candidates for realizing one‐way cryptographic systems that avoid duplication and attacks. However, previous approaches suffer from the tradeoffs between low‐efficiency fabrication and complicated authentication. Here, all‐photonic cryptographic primitives by solution printing of organic nanolaser arrays with size‐dependent dual lasing emission are reported. The stochastic distribution of organic solution into discrete capillary bridges, triggered by high‐rate solvent evaporation, on a periodic topographical template yields organic single crystals with regulated position, alignment, and random size, which ensures high entropy. Stimulated emission from different vibrational sublevels and the intrinsic self‐absorption effect permit size‐dependent dual‐wavelength lasing emission at wavelengths of 660 and/or 720 nm, which can be efficiently encoded into quaternary cryptographic keys with high reliability. High entropy, solution‐processed programming and all‐photonic authentication of random organic nanolaser arrays facilitate their cryptographic implementation in secure communication with high throughput, efficiency, and low cost.     

Towards Infrared Electronic Eyes: Flexible Colloidal Quantum Dot Photovoltaic Detectors Enhanced by Resonant Cavity

Electronic eye cameras are receiving increasing interest due to their unique advantages such as wide field of view, low aberrations, and simple imaging optics compared to conventional planar focal plane arrays. However, the spectral sensing ranges of most electronic eyes are confined to the visible, which is limited by the energy gaps of the sensing materials and by fabrication obstacles. Here, a potential route leading to infrared electronic eyes is demonstrated by exploring flexible colloidal quantum dot (CQD) photovoltaic detectors. Benefitting from their tunable optical response and the ease of fabrication as solution processable materials, mercury telluride (HgTe) CQD detectors with mechanical flexibility, wide spectral sensing range, fast response, and high detectivity are demonstrated. A strategy is provided to further enhance the light absorption in flexible detectors by integrating a Fabry–Perot resonant cavity. Integrated short‐wave IR detectors on flexible substrates have peak D^* of 7.5 × 10¹⁰ Jones at 2.2 µm at room temperature and promise the development of infrared electronic eyes with high‐resolution imaging capability. Finally, infrared images are captured with the flexible CQD detectors at varying bending conditions, showing a practical approach to sensitive infrared electronic eyes beyond the visible range.     

In‐situ Messung dünner Schichten auf Architekturglas

For the deposition of modern coatings on architectural glass (energy‐saving, solar control, anti‐reflective), reactive magnetron sputtering plays an outstanding role. The production of these coatings by reactive sputtering requires a manufactoring equipment, that ensures high quality as well as efficient deposition of the coatings. Thin film measurement by in‐situ ellipsometry can very impressively used for monitoring and controlling the film properties, in particular in the case of more complex coatings. With regard to long‐term stability the in‐situ film measurement is of special importance with respect to the use of the novel mid‐frequency magnetron sputter technique. This technique allows the deposition rate to be increased up to 500 %, however, a dynamical plasma stabilization in the so called »transition mode« is necessary. Within the framework of a project supported by the BMBF, the spectroscopic ellipsometry was implemented on a large scale glass deposition plant (Semco Glasbeschichtung, Neubrandenburg) and was tested during the production. The investigations show that ellipsometry is outstandingly suitable for an accurate determination of the optical layer properties of coatings on architecture glass, even for complex layer systems. Therefore, the basis for an improvement of the efficiency of the plant is given.     

A Novel Multi‐hidden Semi‐Markov Model for Degradation State Identification and Remaining Useful Life Estimation

With the increase of product reliability, collecting time‐to‐failure data is becoming difficult, and degradation‐based method has gained popularity. In this paper, a novel multi‐hidden semi‐Markov model is proposed to identify degradation and estimate remaining useful life of a system. Multiple fused features are used to describe the degradation process so as to improve the effectiveness and accuracy. The similarities of the features are depicted by a new variable combined with forward and backward variables to reduce computational effort. The degradation state is identified using modified Viterbi algorithm, in which linear function is adopted to describe the contribution of each feature to the state recognition. Subsequently, the remaining useful life can be forecasted by backward recursive equations. A case study is presented, and the results demonstrate the validity and effectiveness of the proposed method. Copyright © 2012 John Wiley & Sons, Ltd.     

Cholesteric Liquid Crystal Shells as Enabling Material for Information‐Rich Design and Architecture

The responsive and dynamic character of liquid crystals (LCs), arising from their ability to self‐organize into long‐range ordered structures while maintaining fluidity, has given them a role as key enabling materials in the information technology that surrounds us today. Ongoing research hints at future LC‐based technologies of entirely different types, for instance by taking advantage of the peculiar behavior of cholesteric liquid crystals (CLCs) subject to curvature. Spherical shells of CLC reflect light omnidirectionally with specific polarization and wavelength, tunable from the UV to the infrared (IR) range, with complex patterns arising when many of them are brought together. Here, these properties are analyzed and explained, and future application opportunities from an interdisciplinary standpoint are discussed. By incorporating arrangements of CLC shells in smart facades or vehicle coatings, or in objects of high value subject to counterfeiting, game‐changing future uses might arise in fields spanning information security, design, and architecture. The focus here is on the challenges of a digitized and information‐rich future society where humans increasingly rely on technology and share their space with autonomous vehicles, drones, and robots.     

Tunable Resonator‐Upconverted Emission (TRUE) Color Printing and Applications in Optical Security

Lanthanide‐doped nanophosphors are promising in anti‐counterfeiting and security printing applications. These nanophosphors can be incorporated as transparent inks that fluoresce by upconverting near‐infrared illumination into visible light to allow easy verification of documents. However, these inks typically exhibit a single luminescent color, low emission efficiency, and low print resolutions. Tunable resonator‐upconverted emission (TRUE) is achieved by placing upconversion nanoparticles (UCNPs) within plasmonic nanoresonators. A range of TRUE colors are obtained from a single‐UCNP species self‐assembled within size‐tuned gap‐plasmon resonances in Al nanodisk arrays. The luminescence intensities are enhanced by two orders of magnitude through emission and absorption enhancements. The enhanced emissive and plasmonic colors are simultaneously employed to generate TRUE color prints that exhibit one appearance under ambient white light, and a multicolored luminescence appearance that is revealed under near‐infrared excitation. The printed color and luminescent images are of ultrahigh resolutions (≈50 000 dpi), and enable multiple colors from a single excitation source for increased level of security.     

Verschleißreduzierung an Matrizen für das Präzisionsschmieden von Zahnrädern durch Mehrlagenhartstoffbeschichtung (TiN‐TiCN‐TiC)

Wear reduction on dies for precision forging of gear wheels by means of multi‐layer coating (TiN‐TiCN‐TiC) Due to high thermal, mechanical and tribological loads the tool life quantity of hot forging dies compared to other manufacturing processes is relatively low. Depending on the number of forged parts the mentioned loads lead to different failure causes of the dies. In this connection wear is the main failure cause of hot forging dies. Especially in the precision forging process of gear wheels with its exacting tolerances the tool life quantity is low, which leads to often interruptions of the production process. Because wear concentrates on the near‐surface die areas, these problems can be reduced by increasing the wear resistance of these areas by the Duplex PACVD‐Method, which means nitriding and multi‐layer coating (TiN‐TiCN‐TiC).     

Mixed‐mode delamination in 2D layered beam finite elements

In this work, a 2D finite element (FE) formulation for a multi‐layer beam with arbitrary number of layers with interconnection that allows for mixed‐mode delamination is presented. The layers are modelled as linear beams, while interface elements with embedded cohesive‐zone model are used for the interconnection. Because the interface elements are sandwiched between beam FEs and attached to their nodes, the only basic unknown functions of the system are two components of the displacement vector and a cross‐sectional rotation per layer. Damage in the interface is modelled via a bi‐linear constitutive law for a single delamination mode and a mixed‐mode damage evolution law. Because in a numerical integration procedure, the damage occurs only in discrete integration points (i.e. not continuously), the solution procedure experiences sharp snap backs in the force‐displacements diagram. A modified arc‐length method is used to solve this problem. The present model is verified against commonly used models, which use 2D plane‐strain FEs for the bulk material. Various numerical examples show that the multi‐layer beam model presented gives accurate results using significantly less degrees of freedom in comparison with standard models from the literature. Copyright © 2015 John Wiley & Sons, Ltd.