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Thin-film optical filters
01 Jan 1969-
TL;DR: In this paper, the authors present a theoretical analysis of thin-film dielectric materials and apply it to filter and coating applications, showing that layer uniformity and thickness monitoring are important factors affecting layer and coating properties.
Abstract: Introduction. Basic theory. Antireflection coating. Neutral mirrors and beam splitters. Multilayer high-reflectance coatings. Edge filters. Band-pass filters. Tilted coatings. Production methods and thin-film materials. Factors affecting layer and coating properties. Layer uniformity and thickness monitoring. Specification of filters and environmental effects. System considerations: applications of filters and coatings. Other topics. Characteristics of thin-film dielectric materials.
Citations
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TL;DR: The photoluminescence properties of porous silicon have attracted considerable research interest since their discovery in 1990 as discussed by the authors, which is due to excitonic recombination quantum confined in Si nanocrystals which remain after the partial electrochemical dissolution of silicon.
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TL;DR: A simple aperiodic array of silicon nanotips on a 6-inch wafer with a sub-wavelength structure that can suppress the reflection of light at a range of wavelengths from the ultraviolet, through the visible part of the spectrum, to the terahertz region is reported.
Abstract: Nature routinely produces nanostructured surfaces with useful properties, such as the self-cleaning lotus leaf, the colour of the butterfly wing, the photoreceptor in brittlestar and the anti-reflection observed in the moth eye. Scientists and engineers have been able to mimic some of these natural structures in the laboratory and in real-world applications. Here, we report a simple aperiodic array of silicon nanotips on a 6-inch wafer with a sub-wavelength structure that can suppress the reflection of light at a range of wavelengths from the ultraviolet, through the visible part of the spectrum, to the terahertz region. Reflection is suppressed for a wide range of angles of incidence and for both s- and p-polarized light. The antireflection properties of the silicon result from changes in the refractive index caused by variations in the height of the silicon nanotips, and can be simulated with models that have been used to explain the low reflection from moth eyes. The improved anti-reflection properties of the surfaces could have applications in renewable energy and electro-optical devices for the military.
1,012 citations
TL;DR: In this article, the windows of parameters required to produce high density parts from AlSi10Mg alloy using selective laser melting were investigated and a compromise between the different parameters and scan strategies was achieved and used to produce parts achieving a density of 99.8%.
Abstract: Selective laser melting (SLM) is widely gaining popularity as an alternative manufacturing technique for complex and customized parts. SLM is a near net shape process with minimal post processing machining required dependent upon final application. The fact that SLM produces little waste and enables more optimal designs also raises opportunities for environmental advantages. The use of aluminium (Al) alloys in SLM is still quite limited due to difficulties in processing that result in parts with high degrees of porosity. However, Al alloys are favoured in many high-end applications for their exceptional strength and stiffness to weight ratio meaning that they are extensively used in the automotive and aerospace industries. This study investigates the windows of parameters required to produce high density parts from AlSi10Mg alloy using selective laser melting. A compromise between the different parameters and scan strategies was achieved and used to produce parts achieving a density of 99.8%.
949 citations
TL;DR: In this article, a review of the evolution of single-photon detectors based on superconducting nanowires (SSPDs) is presented, and a detailed snapshot of an emerging superconducted detector technology on the threshold of maturity is presented.
Abstract: Single-photon detectors based on superconducting nanowires (SSPDs or SNSPDs) have rapidly emerged as a highly promising photon-counting technology for infrared wavelengths. These devices offer high efficiency, low dark counts and excellent timing resolution. In this review, we consider the basic SNSPD operating principle and models of device behaviour. We give an overview of the evolution of SNSPD device design and the improvements in performance which have been achieved. We also evaluate device limitations and noise mechanisms. We survey practical refrigeration technologies and optical coupling schemes for SNSPDs. Finally we summarize promising application areas, ranging from quantum cryptography to remote sensing. Our goal is to capture a detailed snapshot of an emerging superconducting detector technology on the threshold of maturity.
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References
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TL;DR: In this article, the authors give the equivalent indices for some commonly used periods, such as symmetric thin-film combinations, which are useful in the design of optical filters and antireflection coatings.
Abstract: According to Herpin’s theorem, a symmetrical thin-film combination is equivalent, at one wavelength, to a single film, characterized by an equivalent index and equivalent thickness. If a large number of identical nonabsorbing thin-film combinations are combined, the resulting periodically stratified medium acts as a band-stop filter. In a stop band, the equivalent index of a symmetrical period is a pure imaginary; in a pass band, it is real. Equivalent indices are given for some commonly used periods. These may have values not possessed by any existing substance. These periods have proved useful in the design of optical filters and antireflection coatings.
240 citations
"Thin-film optical filters" refers background or methods in this paper
...Heavens [1], Holland [2], Anders [3], Knittl [4] are just some of those that will repay study, and they are listed in the bibliography along with some more recent volumes....
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...This can be vacuum deposited, or the aluminium at the surface of the coating can be anodised by an electrolytic technique [1], forming a very hard layer of aluminium oxide....
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...[1] Cox J T and Hass G 1958 Antireflection coatings for germanium and silicon in the infrared J....
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...F A function used in the theory of the Fabry–Perot interferometer....
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...It can be used as a longwave-pass filter, a shortwave-pass filter, a bandstop filter, a straightforward high-reflectance coating, for example in laser mirrors, and as a reflector in a thin-film Fabry–Perot interferometer (figure 1.3), which is another basic filter type described in some detail in chapters 5 and 7....
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TL;DR: The development of stress in evaporated dielectric and metal films, used as optical coatings, has been investigated experimentally by observing the bending of a thin silica strip as it becomes coated.
Abstract: The development of stress in evaporated dielectric and metal films, used as optical coatings, has been investigated experimentally by observing the bending of a thin silica strip as it becomes coated. The strip forms one mirror of a laser interferometer mounted within the coating chamber, giving high measurement sensitivity. Stress data on a number of materials commonly used in coating are presented, and the behavior of multilayer coatings investigated. Analysis of the effect of film stress upon the figure of optical surfaces is given, and the influence of stress upon the mechanical stability of multilayers is discussed.
197 citations
TL;DR: In this paper, the authors introduced the concept of induced transmission and applied it directly to the problem of improving the efficiency of metal band pass filters, and the resulting designs were discussed from different points of view.
Abstract: The potential transmittance of a given absorbing film depends only on the load admittance of the optical structure with which it is backed, in addition to the optical parameters of the film itself. Utilizing appropriately designed backings of nonabsorbing multilayer films, admittances for light of a specified wavelength can be obtained which greatly increase the potential transmittance of certain materials, notably metals with high k/n ratios. A high transmittance of the specified monochromatic radiation results if the given film plus backing is subsequently antireflected by a second nonabsorbing multilayer combination added on the side of incidence. This procedure introduces the basic principles of “induced transmission.” These principles are applied directly to the problem of improving the efficiency of metal band pass filters. The resulting designs are discussed from different points of view.
153 citations
TL;DR: HAL as discussed by the authors is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not, which may come from teaching and research institutions in France or abroad, or from public or private research centers.
Abstract: HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Some factors influencing the adhesion of films produced by vacuum evaporation O.S. Heavens
144 citations
TL;DR: In this paper, the spectral properties of CdS and ZnS in the spectral region from 0.6 micron to 14 microns were determined from spectrophotometric reflectance and transmittance measurements.
Abstract: The index of refraction and the absorption of evaporated films of CdS and ZnS in the spectral region from 0.6 micron to 14 microns were determined from spectrophotometric reflectance and transmittance measurements. The index of refraction of CdS ranged from 2.52 at 0.6μ to 2.26 at 14μ and was independent of deposition rate. The index of ZnS varied from 2.34 at 0.6μ to 2.15 at 14μ and was independent of deposition rate. The absorption coefficient of CdS depended upon the deposition rate from 0.6μ to 6μ and increased beyond 6μ independently of deposition rate. The absorption coefficient of ZnS was approximately 0.001 in the region of investigation. Approximate formulas are given for calculating the index of refraction and absorption from the reflectance and transmittance when the absorption is small. A method is given for preparing the phosphors that yields films for which the index of refraction is independent of the deposition rate. The crystalline structure was investigated by means of x-ray diffraction.
123 citations