Multilayer Reflectors Research Articles

Microwave power penetration enhancement inside an inhomogeneous human head

The penetration of microwave power inside a human head model is improved by employing a dielectric loaded rectangular waveguide as the transmission source. A multi-layer reflection model is investigated to evaluate the combined material characteristics of different lossy human head tissues at 2.45 GHz. A waveguide loaded with a calculated permittivity of 3.62 is shown to maximise the microwave power penetration at the desired frequency. A Quartz (SiO2) loaded rectangular waveguide fed by a microstrip antenna is designed to validate the power penetration improvement inside an inhomogeneous human head phantom. A measured 1.33 dB power penetration increment is observed for the dielectric loaded waveguide over a standard rectangular waveguide at 50 mm inside the head, with an 81.9% reduction in the size of the transmission source.

Visualization of the gas flows that formed above the thin-film coatings under VUV radiation influence

The plasma focus of a magnetoplasma compressor is a unique source of high-brightness broadband VUV (with photon energy of 5 to 100 electron volt) radiation. When such radiation affects on the surfaces of materials, it is possible to generate rather complex gas-dynamic structures due to the evaporation of the material and ionization of its vapors. A separate task is to study the processes of a gas-dynamic response to the exposure of the specified radiation fluxes on the surface of interference antireflection and reflective multilayers, which are used in modern laser technology, high-power optoelectronics, etc. In this report, we used schlieren photography for studying the features of gas-dynamic structures that arise at irradiation of coatings. Radiation resistant (in the visible and near IR ranges) HfO2/SiO2 and ZrO2/SiO2 multilayer structures (with a total thickness of 140–3700 nanometers and a number of layers of from 2 to 24) were used as prototypes for testing their stability under the VUV exposure.

Multilayer Reflective Coatings for BEUV Lithography: A Review.

The development of microelectronics is always driven by reducing transistor size and increasing integration, from the initial micron-scale to the current few nanometers. The photolithography technique for manufacturing the transistor needs to reduce the wavelength of the optical wave, from ultraviolet to the extreme ultraviolet radiation. One approach toward decreasing the working wavelength is using lithography based on beyond extreme ultraviolet radiation (BEUV) with a wavelength around 7 nm. The BEUV lithography relies on advanced reflective optics such as periodic multilayer film X-ray mirrors (PMMs). PMMs are artificial Bragg crystals having alternate layers of “light” and “heavy” materials. The periodicity of such a structure is relatively half of the working wavelength. Because a BEUV lithographical system contains at least 10 mirrors, the optics’ reflectivity becomes a crucial point. The increasing of a single mirror’s reflectivity by 10% will increase the system’s overall throughput six-fold. In this work, the properties and development status of PMMs, particularly for BEUV lithography, were reviewed to gain a better understanding of their advantages and limitations. Emphasis was given to materials, design concepts, structure, deposition method, and optical characteristics of these coatings.

Collimating/focusing optical system designed for hard X-ray communication

A collimating/focusing (C/F) optical system could greatly reduce the power requirements and improve the communication performance in space communication. Based on the known X-ray source, this paper proposed a hard X-ray multilayer collimating/focusing optical system for X-ray communication (XCOM) in 10–30 keV region. The C/F optical system helps effectively realize XCOM with high gain and high signal to noise ratio (SNR) hundreds of kilometers away. This paper discusses the reflectivity of multilayers, the optimization of supermirrors, the design of C/F optical system for hard X-ray, and the ray tracing process. Results shows that the collection efficiency of hard X-ray is greatly improved, and still remains 0.0196% 1000 km away from the X-ray source. When the transmitting power of X-ray is 100 W, the SNR reaches 71.8 dB at 100 km and 50.1 dB at 1000 km, respectively. This work provides some theoretical and actual values for improving the practical application of X-ray communication in entry blackout and space exploration.

Picometer sensitivity metrology for EUV absorber phase

With growing interest in EUV attenuated phase-shift masks due to their superior image quality for applications such as dense contact and pillar arrays, it is becoming critical to model, measure, and monitor the intensity and relative phase of multilayer and absorber reflections. We present a solution based on physical modeling of reflectometry data, which can achieve single picometer phase precision and sensitivity to changes in average film thickness below one atomic monolayer. We measure absorber and multilayer reflectivity to determine thin-film parameters with a multidimensional optimization and then acquire a new measurement of either multilayer or absorber to determine perturbations in surface contamination thickness. While it is difficult to assess the accuracy of the first step, the simplicity of the second step allows us to characterize our sensitivity to changes in contamination thickness. We apply this analysis using an initial set of measurements and repeated measurements after a period of storage. For the multilayer, the total contamination growth was 1068 pm, which occurred almost exclusively during storage (1085 pm) and decreased very slightly during repeated measurements (−17 pm). For the absorber, the behavior was quite different, with a total growth of 126 pm, which occurred much less during storage (28 pm) and primarily during repeated measurements (98 pm). Ultimately, the change in relative phase (absorber minus multilayer) was −0.86 deg for the multilayer and −1.12 deg for the absorber. We estimate the precision of the surface contamination measurement to be 3σ < 6 pm for measuring thickness and 3σ < 0.2 deg for measuring phase.

“Somos contra la ‘queer-ificacíon’”/“We reject the queer-ification of lesbianism”: lesbian political identity and anti-queer politics among Mexican lesbians and queer Chicanas-Latinas

ABSTRACT This essay provides a critical personal reflection contemplating a 2006 Mexico City-based cross- border dialogue in which sharp divisions emerged between a set of Mexicana lesbianas—declaring their pro-lesbian feminist and anti-queer politics—and a set of queer Chicanas- Latinas—pronouncing their queer women of color politics. The vexing exchange occurred on the eve of the 3rd annual Marcha Lésbica, an explicitly radical lesbian feminist political gathering and at the time the largest public action of its kind to be held in Latin America. I draw new insights about key historical and contemporary lesbian political identity issues by reviewing how Mexican lesbian politics informed by feminism and critiques of neoliberalism produced challenges to the U.S. based participants. I reframe the value of the lesbian Mexicanas’ “anti- queer” proclamation, an affective statement especially unpopular in that period given the provincializing glance at lesbian politics and identity in the U.S. Finally, I revisit this difficult moment to historicize how lesbian remains a freighted category of political identity for Chicanas-Latinas who abide by women of color and trans coalitional politics, while it also opens up affinities for meaningful though precarious cross-border identifications. This multilayered reflection argues for a situated understanding of the meanings that can be ascribed to lesbian identity and politics, which are highly contingent upon spatio-temporalities. Thus, the category “lesbian” is replete with instructive energies whether as an affective critique of queer epistemologies that move along a Global North to Global South axis, or as a reminder of the limits of coalitional politics built across nation-state borders.

Design and fabrication of recombinant reflectin-based multilayer reflectors: bio-design engineering and photoisomerism induced wavelength modulation

The remarkable camouflage capabilities of cephalopods have inspired many to develop dynamic optical materials which exploit certain design principles and/or material properties from cephalopod dermal cells. Here, the angle-dependent optical properties of various single-layer reflectin thin-films on Si wafers are characterized within the UV–Vis–NIR regions. Following this, initial efforts to design, fabricate, and optically characterize a bio-inspired reflectin-based multilayer reflector is described, which was found to conserve the optical properties of single layer films but exhibit reduced angle-dependent visible reflectivity. Finally, we report the integration of phytochrome visible light-induced isomerism into reflectin-based films, which was found to subtly modulate reflectin thin-film reflectivity.

How Hands-on Experimentation in Mechanical Textile Recycling Influences Existing Waste Management Systems

A multi-layered critical reflection on how the concept of mechanical textile recycling and hands-on experiments can lead to a more sustainable textile future and at the same time leads to an adaptation of existing systems within the textile value chain. How can a new valuable raw material be obtained from post-consumer textile waste (PCTW)? How can this material be processed and integrated into the textile production chain, and what kind of products can emerge out of it? The discussed applied research project, called Texcycle, was organised by the Product & Textile Research Group at the Lucerne University of Applied Sciences and Arts. The research questions mentioned above were approached step by step with the industry, and new solution strategies were sought in the individual process steps with the partners. The main partners were a textile recycling and sorting company, TEXAID Textilverwertungs AG and the wholesaler Coop Genossenschaft. As the project proceeded, a wool spinner, a nonwoven specialist, and a carpet manufacturer joined for prototyping the products. Texcycle is an Innosuisse financed project that promotes knowledge-based innovation in the interest of the economy and society and supports the collaboration of research institutions and the Swiss industry. Therefore, sustainable textile products produced from local waste streams can act as vehicles for change in the textile industry. The development of products from waste streams is highly complex. In addition to the traditional stakeholder of the textile industry, it also concerns new actors such as the waste and sorting industry, which have to acquire knowledge about the processing of used fibres. The proposed solutions are based on new insights about material composition in the waste stream due to the investigation of fibre content in existing key sorting categories. As a result, new material-orientated sorting categories are proposed, not yet established in the market since the main focus is on types and quality. Due to hands-on material design and development with PCTW, requirements and material properties to replace the virgin stock in the textile production chain were identified. The executed development of yarn and nonwovens in this project demonstrates, on the one hand, feasible future applications and is also a proof of concept from a design and market perspective. The resulting artefacts are key for future adaptation in sorting and production facilities yet an initial change in this complex system. This article focuses on the Soft Systems Methodology (SSM) described by its developer Peter Checkland in relation to the material-led design research project Texcycle dealing with post-consumer textile waste. With its origins in system thinking, the soft-system methodology allows an analysis of complex interlinked structures and further uses models of activity to set up a debate about change.

Multi-Layer Reflectivity Calculation Based Meta-Modeling of the Phase Mapping Function for Highly Reproducible Surface Plasmon Resonance Biosensing.

Phase-sensitive surface plasmon resonance biosensors are known for their high sensitivity. One of the technology bottle-necks of such sensors is that the phase sensorgram, when measured at fixed angle set-up, can lead to low reproducibility as the signal conveys multiple data. Leveraging the sensitivity, while securing satisfying reproducibility, is therefore is an underdiscussed key issue. One potential solution is to map the phase sensorgram into refractive index unit by the use of sensor calibration data, via a simple non-linear fit. However, basic fitting functions poorly portray the asymmetric phase curve. On the other hand, multi-layer reflectivity calculation based on the Fresnel coefficient can be employed for a precise mapping function. This numerical approach however lacks the explicit mathematical formulation to be used in an optimization process. To this end, we aim to provide a first methodology for the issue, where mapping functions are constructed from Bayesian optimized multi-layer model of the experimental data. The challenge of using multi-layer model as optimization trial function is addressed by meta-modeling via segmented polynomial approximation. A visualization approach is proposed for assessment of the goodness-of-the-fit on the optimized model. Using metastatic cancer exosome sensing, we demonstrate how the present work paves the way toward better plasmonic sensors.

Dimensional Transformations of Guided-Mode Resonant Photonic Lattices

Reflection spectra based on guided-mode resonance (GMR) are simulated and discussed with transformation between one-dimensional (1-D) and two-dimensional (2-D) photonic lattices by introducing intermediate structures consisting of vertically-stacked 1-D and 2-D gratings. Dependences of reflection spectra on a 2-D fractional ratio are investigated for two examples of narrowband and broadband resonance elements. Observed complicated spectrum transformations for the narrowband example are successfully explained by combining simple models with guided-mode indices and multilayer reflection. The understanding of the fundamental transformation dynamics will aid in the reflection band engineering for development of new optical components.

Polarization-independent reflection grating in second-order Littrow for high laser resolving power

In order to obtain a grating solution for high laser resolving power, a multilayer fused-silica reflection grating is described with a silver layer embedded in the groove in second-order Littrow configuration instead of first-order mounting. Efficiencies of 96.17% and 96.14% can diffracted in −2nd order for TE and TM polarizations, which are greater than 96%. The new multilayer reflection grating with a silver layer embedded has good incident characteristics and process tolerances. Therefore, the high-efficiency output with polarization-independent and wideband property characteristics of the grating will be well applied to the laser field.

Raman scattering study of nanoscale Mo/Si and Mo/Be periodic multilayer structures

Investigation of the microstructure and phase analysis of the periodic Mo/Si and Mo/Be multilayers are essential for depositing high reflective multilayers that operate at soft x-ray to extreme ultraviolet radiations. Raman spectroscopy revealed the presence of an amorphous phase of silicon (Si) in the Mo/Si multilayers. Furthermore, the disorder of the amorphous Si phase was increased with decreasing the periodic thickness of the Si layers in the nanoscale Mo/Si multilayers. The polycrystalline Mo periodic layers coexisted with the amorphous silicon layers in the Mo/Si multilayers. In contrast, both the Mo and Be layers in the Mo/Be periodic multilayers were condensed into the polycrystalline phases. At higher annealing temperatures, the polycrystalline and amorphous phases in both the Mo/Si and Mo/Be multilayers were destroyed due to the extensive interdiffusion process. However, the amorphous Si phase was partially preserved due to the formation of crystalline intermetallic h-MoSi2 and t-MoSi2 phases, for critically thicker Si layers in periodic Mo/Si multilayers.

Anomalous divergence of the multiple-beam method revisited

The multiple-beam method to evaluate optical multilayer reflection and transmission coefficients suffers divergence under certain conditions. An algorithm based on the concept of reduced layer systems and a mapping of the partial beams to corridor paths was developed to re-gain convergence. Further examples, including the case of frustrated total reflection, demonstrate the variability of the convergence rate. The algorithm provides the means to extend methods specialised to layers with particular properties with the effect of multiple reflections when embedded within a multilayer.

Substanzaktivität. Farbe als prima materia im Andachtsbild der Frühen Neuzeit

Abstract In devotional pictures of the Quattrocento by Giovanni di Francesco Toscani, Fra Angelico, Zanobi Strozzi, Benozzo Gozzoli, and Bartolomeo Caporali, floor and wall fields repeatedly appear as non-representational color grounds. They refer to a hitherto rather insufficiently analyzed multi-layered reflection of the design modes of the time. These surfaces only superficially resemble natural stone structures. Rather, they are coloristic protoforms of the pictorial figurations, which is why these color fields, apart from a theological sub-iconography, can also be understood as references to the substrate character of the color. By evoking spiral and snail shapes in addition to completely amorphous spots, they also seem to reflect the processes of rock formation as explored in Albertus Magnus’s De mineralibus. As a fluid matter that can develop spontaneously into any form in the sense of a painterly generatio spontanea, color finally approximates the Aristotelian concept of hylē. This contribution seeks to explore the exciting and dynamic relationship between matter and form in the quattrocentesque devotional picture. The color substance of the amorphous grounds is understood as an activated source material that is transformed into vivid forms by way of the respective artistic technē.

Design of efficient concave diffraction grating on 220 nm SOI platform for hybrid WDM–PDM​ (de)multiplexing

An efficient concave diffraction grating (CDG) for multi-wavelengths and dual polarizations is proposed and demonstrated on 220 nm SOI platform with systematic analyzation and simulation. The multilayer dielectric reflector is designed as an alternative to conventional deep-etched tooth to provide high reflectance with polarization insensitivity. Simulation results indicate that with proper selection of incident angles, the grating designed by this approach shows excellent performances in terms of diffraction efficiency, channel uniformity and next-channel crosstalk for both TE and TM polarizations. A comparative analysis between different grating tooth configurations and a detailed discussion about the fabrication tolerances are also presented. This design can be applied to wavelength and polarization hybrid multiplexing to further enhance the link capacity of optical transmissions and interconnects.

Structural colours in diverse Mesozoic insects.

Structural colours, nature's most pure and intense colours, originate when light is scattered via nanoscale modulations of the refractive index. Original colours in fossils illuminate the ecological interactions among extinct organisms and functional evolution of colours. Here, we report multiple examples of vivid metallic colours in diverse insects from mid-Cretaceous amber. Scanning and transmission electron microscopy revealed a smooth outer surface and five alternating electron-dense and electron-lucent layers in the epicuticle of a fossil wasp, suggesting that multilayer reflectors, the most common biophotonic nanostructure in animals and even plants, are responsible for the exceptional preservation of colour in amber fossils. Based on theoretical modelling of the reflectance spectra, a reflective peak of wavelength of 514 nm was calculated, corresponding to the bluish-green colour observed under white light. The green to blue structural colours in fossil wasps, beetles and a fly most likely functioned as camouflage, although other functions such as thermoregulation cannot be ruled out. This discovery not only provides critical evidence of evolution of structural colours in arthropods, but also sheds light on the preservation potential of nanostructures of ancient animals through geological time.

Structural colors and physical properties of elytra in the jewel beetle, Chrysochroa fulgidissima, using surface analytical techniques

Structural coloration frequently originates from the interaction of light with multilayers of thin films in living organisms. One example where structural colors are created by multilayers is the jewel beetle, Chrysochroa fulgidissima, which has highly iridescent green elytra with longitudinal red stripes. We examine the structure, chemical information, and physical properties of the epicuticle of the jewel beetle by using atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nanoindentation, and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). AFM and SEM were used to analyze the surface structures of the green elytra and red stripes of the jewel beetle's wing. SEM and TEM images obtained from the cross‐sectioned cuticle samples of green and red areas indicated that the color arises from interference reflectors and reflectors consist of successive repeating layers of different electronic densities. Nanoindentation results showed that the green area of the elytron possesses a higher hardness and reduced modulus compared with the red area. To analyze the surface of the elytra and to compare multilayers of the green area with those of the red area, mass spectra and depth profiles were acquired by ToF‐SIMS with C60 and Ar cluster ion beams. The epicuticle consists of several layers with alternating high and low abundances of inorganic and organic fragment ions, with approximately 16 layers in the green and 12 layers in the red area. Therefore, ToF‐SIMS combined with other analytical techniques indicate that multilayer reflection is a major mechanism of the jewel beetle's iridescence causing structural coloration.

Optical and thermal radiative properties of topological insulator semiconductor multilayers

Topological insulator semiconductors hold unique electronic transport characteristics that allow them behave like graphene at the surface of the nanoscale thin film. Photonic multilayers consisting of alternating layers of topological insulator and layers of its dielectric spacer can be engineered to demonstrate optical and thermal radiative dispersion attributed to electromagnetic metamaterials. This paper presents case studies explain the relationships between material compositions, geometrical factors, spectral functions, and electronic transport mechanisms to the overall visible to far-infrared radiative properties. It shows how topological insulator multilayers could be useful in thermal-photovoltaic components, optoelectronic devices, and radiative coatings. Two multilayer cases are investigated: Bi2Se3-ZnSe, and Bi2Te3-ZnTe. In each, the photon-electron oscillation functions are determined, and spectral dielectric functions are fitted into a modified form of effective medium theory. The spectral and angular radiative properties of different constituent thickness multilayer slabs, reflectance and transmittance, are obtained. The multilayer thin films exhibit good reflection or absorption of visible or infrared wavelength radiation, depending on the tunable constituent film thicknesses and material configurations. Finite-difference time domain simulations demonstrate that these materials could have a negative index of refraction, which results from plasmon polariton coupling between the conductive surface states. The results of these radiative properties indicate that topological insulator multilayers may find their use in solar thermophotovoltaic absorbers, optical band pass filters and sub-diffraction thin film lenses.

Frequency reconfigurable Yagi‐like MIMO antenna system with a wideband reflector

A compact single layer frequency reconfigurable Yagi-like multiple-input multiple-output (MIMO) antenna system is presented based on a half-ring closed loop slot excitation. The traditional omnidirectional pattern of a slot antenna is made directional by using a single slot-based complementary wideband reflector (CWBR) element. The proposed CWBR is compact in size, simple in construction, and is based on a single-layer geometry unlike complex multi-layer reflectors used in the literature. It improves the front-to-back ratio between 5 and 17 dB in the entire frequency range covering 2.5–4.5 GHz. The proposed reconfigurable MIMO antenna system covers the LTE and WiMAX bands with a minimum measured bandwidth of 200 MHz per covered bands. The frequency reconfigurability is achieved by reactively loading the slot loop with varactor diodes. The overall size of the proposed antenna system is 40 × 100 × 0.76 mm 3 , making it suitable for tablet handheld devices and access points. It has a maximum measured peak gain of 5 dBi and total measured radiation efficiency of 78%. The proposed MIMO antenna system has port isolation of > 10 dB within the entire band of operation. The radiation patterns are isolated in space from each other and ensure very low envelope correlation coefficient.

WOW – a multilayered reflection on collective movements

Through a collective writing five dance artists share their individual and common experiences of collective, weaving together an intricate body of text. A playful and sincere approach towards different collective settings, modes and textures, exploring the rich complexity of being many in one – what it can entail, unfold and generate