Metal Mirrors Research Articles

Analysis of metallic slotted micromirrors using modal decomposition and multiple reflections

Micromirrors are essential elements in many photonic systems. The state-of-the-art technology provides micromachining of different types of micromirrors such as Bragg, metallized, and slotted metallic mirrors. The slotted metallic mirrors are thought to overcome some of the drawbacks of the other types that include limited bandwidth, sensitivity to fabrication tolerance, and dielectric material absorption. We propose a model that accounts for the slit thickness and width, incident light profile and polarization in addition to the multiple reflections inside the slit using modal decomposition. The model results are compared to finite-difference–time domain simulations and a good matching is obtained. The model successfully quantifies the transmission below cutoff in the TE polarization for perfectly conducting metallic boundaries. The model also quantifies the Fabry–Pérot-like resonances in the transmission of TM polarized light.

Laser‐Induced Tuning and Spatial Control of the Emissivity of Phase‐Changing Ge2Sb2Te5 Emitter for Thermal Camouflage

AbstractThe tuning of a material's emissivity in the atmospheric window range of 8–13 µm is crucial for infrared (IR) adaptive applications such as thermal camouflage, IR stealth, and radiative cooling. A resonator structure comprising a phase‐changing Ge2Sb2Te5 (GST) film on a metal mirror is promising as a tunable thermal emitter because its long‐wavelength IR emissivity can be varied by adjusting the degree of crystallization of the GST film through annealing. However, the space‐selective tuning of the emissivity required for practical use remains a significant challenge. Herein, a hybrid method combining laser irradiation and heat treatment is presented for space‐selective and continuous tuning of the emissivity of a GST‐based resonator. The current study shows that a laser‐induced crystalline layer formed in the near‐surface region of a 400 nm thick amorphous GST film can act as heterogeneous nuclei for crystallization when the film is subsequently annealed, thereby increasing the crystallization rate of the GST film. This results in a large difference in emissivity between the irradiated and nonirradiated areas, and the emissivity difference can be tuned by changing the annealing temperature. Thermal camouflage is experimentally demonstrated by making high‐and low‐temperature regions with low and high emissivity, respectively.

Раннескифское погребение с металлическим зеркалом из Северного Алтая

The article is devoted to the introduction into scientific circulation and cultural and chronological interpretation of object No. 20 of the Karban-I necropolis. This complex, located in the Chemal district of the Altai Republic, was partially explored in 1989-1990 by expedition of the Barnaul State Pedagogical University (now Altai State Pedagogical University). During the excavations of mound No. 20, located in the western part of the necropolis, a burial of a young woman in a stone box was revealed. An analysis of the recorded signs of ritual practice allows us to attribute this object to the Biyke archaeological culture of the early Scythian period. The appearance of the accompanying inventory, which includes a few decorations, as well as a metal mirror, is also characteristic of the object complex of the nomads of the indicated period. Taking into account the recorded characteristics of the complex, as well as the results of radiocarbon dating, it seems possible to determine the period of construction of the published burial within the second half of the 8th — first half of the 6th centuries BC.

Зеркало в погребальном обряде ранних кочевников Южного Урала: маркер гендера или статуса, предмет культа или быта?

Metal (presumably bronze) mirrors are rather numerous in the early nomadic burials. This study pursues two goals: (1) analysis of burials with mirrors based on the representative data base from the Southern Ural area (the end of the 6th—2nd centuries BCE) and (2) interpretation of symbolism related to mirrors in the mortuary context. The sample consists of 90 anthropologically identified undisturbed burials with mirrors. Of these, 75 burials belonged to females (83.3 %), 11 — to males (12.2 %) and 4 — to sub-adults (4.5 %). The author has analyzed the distribution of objects according to age/gender groups and the correlation between mirrors and other grave goods (ornaments, weapons and cultic items). As a result, we can conclude that mirrors are artifacts of complex symbolism, being objects of everyday life, vertical status and cult, at the same time. It can be confirmed by their position near the head or to the right of the body, the finds of precious and rare mirrors, as well as the location of mirrors in complexes of various objects of cult.

РАЗРАБОТКА УСОВЕРШЕНСТВОВАННЫХ АЛГОРИТМОВ УПРАВЛЕНИЯ ЭЛЕКТРИЧЕСКИМИ РЕЖИМАМИ УСТАНОВОК КОВШ-ПЕЧЬ С АНАЛИЗОМ ГАРМОНИЧЕСКОГО СОСТАВА ТОКОВ ДУГ

The aim of this research is the design of improved control algorithms for ladle furnaces, considering arc length adaptation to different argon blow conditions and slag layer depth. The paper considers the issues of optimizing asymmetric arc burn-ing regimes, which ensure the maximum reduction in radiation and an increase in thermal efficiency in phases located near the liquid metal mirror during bottom blowing and emergency lance operation. The experimental results of liquid bath sur-face behavior in dependence from blowing intensity and slag layer depth are presented. On the basis of experimental re-sults, new algorithms of electric modes control in ladle furnaces are proposed. These algorithms allow dynamic adaptation of electric arc lengths to different argon blowing modes and slag layer depth to be provided. Applying of this algorithm al-lows the requisite conditions for improving of different quality indicators in ladle furnace to be ensured, since the correct adaptation of electric mode to varying conditions of melting has a direct con-nection with thermal efficiency of electric arcs and efficiency of equipment in general.

Direct laser writing of optical gratings on additive manufactured metal surfaces

Enhancing the functionality of surfaces has increasingly become the focus of modern engineering in recent years. Functional material surfaces can be developed through targeted micro structuring. For example, surface modifications by micro structuring can change the wetting behaviour or effectively optimize the frictional properties. Some of these applications are already established on the market and e.g. used in case of improving highly stressed surfaces. To accelerate further research in this direction, the present work deals with the functionalization of surfaces with the aim of modifying optical properties. The overall vision for this is the production of functional enhanced additive manufactured free-form mirrors for technical applications. Nowadays, the additive manufactured metal mirrors need a complicated and time-consuming mechanical post-processing like e.g. manual polishing. To add a further functionalization, structures like e.g. optical gratings need a separate production step, mostly limited to one fix structure geometry and size. Thus, laser direct writing as an alternative method and highly flexible production process is examined.

База данных «Металлические зеркала из музеев Алтайского края и Республики Алтай»

The article discusses the experience of creating a database of metal mirrors originating from the territory of Altai. The electronic resource contains key information about 147 items from the stock collections of six museums in the Altai Territory and the Altai Republic. For the most complete systematization, 28 fields were formed, reflecting important information about each find.

Optimized Design and Additive Manufacture of Double-Sided Metal Mirror with Self-Supporting Lattice Structure

Optimized Design and Additive Manufacture of Double-Sided Metal Mirror with Self-Supporting Lattice Structure

Mathematical study for an electrodeposition model using the topological degree

Electrodeposition is a low-cost and malleable technique for manufacturing a wide diversity of equipment and materials including coatings and films. It was initially operated to prepare metallic mirrors and corrosion resistant surfaces among other things. We consider a 1D (1 dimensional) stationary problem, that is a mathematical model derived from nickel-iron alloy electrodeposition's chemical reactions.The aim of this paper is to provide a mathematical study of the stationary one dimensional case problem using the topological degree.

Update on the characterisation of the pGCT, a prototype of 4m dual-mirror Cherenkov Telescope

The Gamma-ray Cherenkov Telescope prototype (pGCT) is a prototype of an Imaging Atmospheric Cherenkov Telescope, developed as Small-Sized Telescope (SST) of 4m during the preparation of the Cherenkov Telescope Array (CTA). Based on a Schwarzschild-Couder dual-mirror optical design aiming to provide an optimised Point Spread Function (PSF) on a wide field, it had its first Cherenkov light on the Meudon site of the Observatoire de Paris in 2015. Since the decision of CTA to harmonize its future SSTs, the pGCT instrument and the experience gained with its development are now used by the Observatoire de Paris team to provide a test bench for Cherenkov astronomy and a pedagogical tool for educational purposes in Meudon. This paper briefly describes the design of the pGCT and presents the latest advances in the optics of the prototype and its characterisation, directly related to the implementation of new high-quality metallic mirrors carried out since 2020.

Characterization of materials using the secondary electron energy spectromicroscopy technique

This paper presents experimental results to show how secondary electron (SE) energy spectroscopy inside a scanning electron microscope (SEM) might become a useful tool for characterising optical materials. It demonstrates how SE energy spectroscopy can quantify and analyse the build-up of hydrocarbon contamination layers on metal surfaces, potentially useful for monitoring the degradation of metallic mirror coatings. Experimental results are presented to illustrate how the SE energy spectral method can be used to measure dopant concentration in bulk semiconductor samples and the in-built voltage of pn junction heterojunctions. This capability, together with the SEM's ability to provide high spatial resolution, points towards SE energy spectroscopy becoming a powerful analytical technique for quantitatively mapping optoelectronic semiconductors parameters on the nanoscale.

Design and Fabrication Technology of Metal Mirrors Based on Additive Manufacturing: A Review

In recent years, much progress has been made on the development of metal mirrors based on additive manufacturing (AM). The sandwich mirror is well known for its excellent mechanical properties and challenging machining. Now, AM can be used to fabricate this complex structure and reduce the processing time and cost. In addition, with the aid of some new design methods for additive manufacturing, such as lattice, topology optimization (TO), and Voronoi, the freedom of mirror structure design is enormously improved. The common materials of mirrors include ceramics (SiC), glasses (glass ceramics, fused silica), and metals (aluminum, beryllium). Among them, the AM technology of metals is the most mature and widely used. Researchers have recently extensively developed the new-generation metal mirror to improve performance and lightweight rate. This review focuses on the following topics: (1) AM technologies and powder materials for metal mirrors, (2) recent advances in optomechanical design methods for AM metal mirrors, (3) challenges faced by AM metal mirrors in fabricating, and (4) future trends in AM metal mirrors.

Used For Space Irradiation Environment Simulation Equipment Property Analysis of Metal Mirror

With the development of space science and technology, the requirements of spacecraft environment simulation tests are gradually increasing, and radiation environment simulation has also attracted much attention. Based on space radiation environment simulation equipment of vertical metal reflector material in the solar simulator performance analysis, the systematic analysis of the influence factors of metal reflector, aimed at straight metal mirror blank material performance analysis, including the mechanics analysis and optical analysis, the performance to the blank material for testing. The test results show that the aluminum alloy 6061T6 billet used in the metal mirror can meet the requirements of high irradiation vertical solar simulator, and lay a solid foundation for the subsequent solar irradiation simulation, space illumination simulation and spacecraft thermal environment simulation.

Creation of aerosolized detergent compositions for protecting high-precision metal mirrors from the impact of adverse climate factors

This article is devoted to creation of aerosolized detergent compositions, needful for use during operation of high-precision metal mirrors, as a rule, in field conditions. The created detergent compositions with inhibitory properties allow, simultaneously with carrying out the process of physicochemical cleaning of optical surface from technological impurities, to ensure its protection from the influence of adverse climatic factors during storage, transportation, installation and exploitation of the element with the possibility of its alignment. The high climatic resilience of the protective films investigated in this article, which are formed during the cleaning of the optical surface, is shown. In this case, the optical characteristics of the processed elements after climatic tests do not get worse.

Microprocesses at the brass surface after impact of scanning beam of pulse-frequency ultraviolet nanosecond laser

A mode of laser heat treatment of the brass surface prior to conducting of diffusion bonding is proposed. We used the frequency-pulse radiation of a nanosecond ultraviolet laser at a pulse energy density W = 0.15 - 0.52 J/cm2. The metal sample was moved relative to a stationary laser beam along a raster trajectory (“snake”) so that adjacent spots were overlapped with an overlap ratio of ⩾ 99 %. The impact of radiation on brass was carried out in a subthreshold mode excluding crater formation. The process took place while the metal remained in a condensed state. A regular rough structure with a height of individual uplifts of the order of 1 micron was formed on the surface of the brass. article is devoted to creation of aerosolized detergent compositions, needful for use during operation of high-precision metal mirrors, as a rule, in field conditions. The created detergent compositions with inhibitory properties allow, simultaneously with carrying out the process of physicochemical cleaning of optical surface from technological impurities, to ensure its protection from the influence of adverse climatic factors during storage, transportation, installation and exploitation of the element with the possibility of its alignment. The high climatic resilience of the protective films investigated in this article, which are formed during the cleaning of the optical surface, is shown. In this case, the optical characteristics of the processed elements after climatic tests do not get worse.

Development of an ultraprecision metal mirror on additively manufactured Ti-6Al-4V.

Metal mirrors for precise optical applications are commonly fabricated by coating of a metal base substrate with a nickel-phosphorus alloy (NiP). The NiP layer is then processed by precision diamond turning and polishing to obtain a high-quality mirror surface. In this work, Ti-6Al-4V samples that were made by additive manufacturing, also called 3D printing, were used as a base for the development of metal mirrors. The additively manufactured samples were electroplated with a NiP coating and machined using single-point diamond turning (SPDT) to obtain a flat mirror with optical quality and low form error surface. The periodic structure of the SPDT toolmark was then removed by polishing postprocessing. Polishing optimization was first performed on NiP-coated aluminum test samples to find an optimal polishing setup. Based on this optimization, postprocessing of titanium samples was carried out by pitch polishing in combination with 1, 0.25, and 0.1µm diamond slurries. Using this polishing processing, a scratch-free surface was attained with surface microroughness below 0.5 nm.

Mirror-enhanced directional out-coupling of SERS by remote excitation of a nanowire-nanoparticle cavity

We report on the experimental observation of mirror-enhanced directional surface-enhanced Raman scattering (SERS) from a self-assembled monolayer of molecules coupled to a nanowire-nanoparticle (NW-NP) junction on a mirror in a remote excitation configuration. Placing the NW-NP junction on a metallic mirror generates multiple gap plasmon modes that have unique momentum space-scattering signatures. We perform Fourier plane imaging of the SERS from the NW-NP on a mirror to understand the effect of multiple hotspots on molecular emission. We systematically study the effect of the ground plane on the directionality of emission from the NW-NP junction and show that the presence of a mirror drastically reduces the angular spread of emission. The effect of multiple hotspots in the geometry on the directionality of the molecular emission is studied using 3D numerical simulations. The results presented here will have implications in understanding plasmon hybridization in the momentum space and its effects on molecular emission.

Tunable nonreciprocal thermal emitter based on metal grating and graphene

Various nonreciprocal thermal emitters, which provide opportunities for higher energy conversion efficiency, have been proposed to completely violate the traditional Kirchhoff's law. However, the tunable nonreciprocal thermal emitters remain barely investigated. In this paper, by sandwiching a graphene monolayer between a top metallic grating and a bottom magneto-optical film backed with a metallic mirror, we achieve tunable nonreciprocal radiation effect. It is shown that strong nonreciprocal radiation for graphene under initial state is realized at wavelength around 14.845 μm when the incident angle is 30° and the external magnetic field is 3 T. The physical origin behind such phenomenon is disclosed by investigating both the distribution of magnetic field at the resonant peak and the coupled-mode theory. Besides, the nonreciprocal radiation performance remains perfectly within certain range of structure parameters, which is benefit for practical fabrication and applications. More importantly, the strong nonreciprocal radiation of the proposed scheme can be flexibly tuned by the gate voltage of graphene without redesigning and refabricating the structure. We believe that this work will provide new approaches for the design of novel energy harvesting systems and nonreciprocal thermal emitters.

Mechanically Tunable Terahertz Metamaterial Perfect Absorber

The development of a wide range of technologies based on terahertz (THz) electromagnetic radiation drives a strong demand for flexible optical elements. Metasurfaces based on metallic resonators offer a versatile toolkit that permits easy tuning over a wide spectral range by the geometric design. Herein, a mechanically tuned metasurface perfect absorber comprised of split‐ring resonators in combination with a metallic mirror in a microcavity arrangement, is demonstrated. By mechanically tuning the length of the microcavity in the range of 10 μm and above, precise control over the perfect absorption condition is exhibited. A maximum recorded extinction of 45.8 dB is obtained at the perfect absorption condition, corresponding to a suppression of the reflected radiation by almost five orders of magnitude. Experiments are performed in a reflection arrangement using a terahertz time‐domain spectrometer. Simulations of the experimental arrangement show that near‐field effects are weak and the enhancement of metamaterial perfect absorption is in agreement with purely interferometric effects.

Enhanced Emission from Interlayer Excitons Coupled to Plasmonic Gap Cavities.

The emergence of interlayer excitons (IEs) from atomic layered transition metal dichalcogenides (TMDCs) heterostructures has drawn tremendous attention due to their unique and exotic optoelectronic properties. Coupling the IEs into optical cavities provides distinctive electromagnetic environments which plays an important role in controlling multiple optical processes such as optical nonlinear generation or photoluminescence enhancement. Here, the integration of IEs in TMDCs into plasmonic nanocavities based on a nanocube on a metallic mirror is reported. Spectroscopic studies reveal an order of magnitude enhancement of the IE at room temperature and a 5-time enhancement in fluorescence at cryogenic temperatures. Cavity modeling reveals that the enhancement of the emission is attributed to both increased excitation efficiency and Purcell effect from the cavity. The results show a novel method to control the excitonic processes in TMDC heterostructures to build high performance photonics and optoelectronics devices.