bluuebunny/crossref_metadata_2025 huggingface dataset:
Absolute testing of spherical surfaces
Authors: Selberg Lars A.
Published: February 2023

Metrology of spherical surfaces for form error at the <λ/20 level requires reference surfaces which exceed this surface quality. To certify optics and references in this regime, some type of absolute testing is required. Absolute testing of spheres by interferometry has appeared several times in the technical literature. The procedure was originally proposed for the Twyman-Green interferometer and later applied to Fizeau interferometers.1,2,3 It requires three measurements of the part: two at the confocal position, rotating the part 180° between measurements and one measurement at the cat's-eye (point focus) position(see Figure 1).
Absolute testing of spherical optics
Authors: Evans Chris J. , Parks Robert E.
Published: February 2023

Interferometric testing of tight tolerance optics commonly requires correction for the errors introduced into the system by the reference surface (commonly referred to as a 'transmission sphere' in commercially available Fizeau phase measuring interferometers (PMIs)). The process of subtracting the reference surface errors from the measured wavefront is commonly, if somewhat misleadingly, referred to as 'absolute testing'. Absolute testing of flats was discussed at the 1992 Optical fabrication and Testing workshop. Here we consider spherical optics.
Recent and Upcoming Environmental Developments in the Optics Industry
Authors: Popham William B. , Ford Libby
Published: February 2023

As the 1990s mature, voluntary compliance and market-based incentives are receiving increasing emphasis by state and federal agencies. This is particularly true because of the newly emerging emphasis on meeting environmental protection goals in a less than satisfactory business climate. During 1994, congressional debate on such environmental programs as the Clean Water Act (CWA) and the Comprehensive Environmental Response, Compensation and Liability Act (Superfund) will increasingly focus on economic issues. Because of the growing attention being paid to unfunded mandates and their effect on local resources, legislators and regulators will be addressing the issue of “who pays and how” when considering additional environmental requirements and deadlines for compliance with these new requirements. For these reasons, pollution prevention, waste minimization, energy efficiency, and total environmental quality management will become legislative and regulatory buzz words, designed, at least at the public-relations level, to encourage companies to take the lowest-cost approach to environmental improvement.
Elimination of Ozone-Depleting Substances and Thorium Fluoride from Infrared Optical Components
Authors: Platt George , Sulzbach Frank , Harmon Rick , Vakiner John
Published: February 2023

World-wide attention to reduction of Ozone-Depleting Substances (ODS) requires redesigning many optical fabrication processes to eliminate or drastically reduce ODS usage. We will discuss progress toward the goal of the Texas Instruments Optical Fabrication and Coating Facility to be ODS-free by the end of 1994. There are similar pressures to eliminate the mildly radioactive Thorium Fluoride coating material often used when coating infrared optics. We will describe the scope of coating redesign required and the measured results of new Thorium-Free coatings. We will describe the mixed hazardous waste minimization program required to continue repair of customer returns and results of decontaminating our equipment and facilities during 1992.
Limits in Aspheric Metrology
Authors: Evans Chris J.
Published: February 2023

What are the minimum uncertainties the metrologist can associate with the measurement of aspheric surface? Some limits are independent of, and others specific to, the measurement approach. Both are discussed.
Requirements for LIGO Optics and Their Realization
Authors: Kells William P.
Published: February 2023

The scientific goals of the Laser Interferometric Gravitaional-wave Observatory (LIGO) project are to detect and study gravitational waves as they pass by the earth. Like electromagnetic waves they are transverse excitations propagating at the speed of light. LIGO is sensitive to a low frequency gravitational radiation band, 0.1 - 10 kHz, predicted to include the characteristic modes of cataclysmic astrophysical sources of interest. These waves produce a local strain in space [time] analogous to the electric field stress in light. This appears as any other mechanical strain and is detected by measuring change in spatial separations of reference points (e.g. mirror surfaces).
Phase Shifting Point Diffraction Interferometry of Lithographic Optics
Authors: Medecki Hector , Attwood David , Tejnil Edita , Goldberg Kenneth A. , Beguiristain Raul , Bokor Jeffrey
Published: February 2023

The Center for X-Ray Optics is performing metrology of optics intended to be used for lithography at wavelengths in the Extreme Ultraviolet (EUV) range. The source for this radiation is an undulator operating at the Advanced Light Source (ALS). Initially a Point Diffraction Interferometer (PDI) was used and the experience acquired with this instrument led to the development of a new interferometer, the Phase Shifting Point Diffraction Interferometer (PSPDI), to be described in this paper.
Optical polishing of the VLT 8.2m primary mirrors - A report
Authors: Geyl Roland , Paseri Jacques
Published: February 2023

The European Southern Observatory (ESO) Very Large Telescope (VLT) project is an array of four 8m class telescopes which can operate either independently or in interferometric mode. Figure 1 is a sketch of one 8m telescope in its enclosure. Unit telescopes are of the Ritchey-Chrétien type, with the pupil on the secondary mirror.
Fabrication of the 1.2 m Secondary Mirror for the Sloan Digital Sky Survey
Authors: Smith B. K. , Burge J. H. , Martin H. M.
Published: February 2023

The 1.2 m secondary mirror for the Sloan Digital Sky Survey Telescope (SDSS) is the first mirror to be fabricated using a new process and facility at the Steward Observatory Mirror Lab. We write this summary during the loose-abrasive grinding stage, which is guided by mechanical profilometry. At the meeting we will present the status of polishing and optical testing.
Calculations of Relative Velocity in Abrasive Wear Systems Employing Laps of Constant Radius of Curvature
Authors: Brown Norman J. , Taylor John S.
Published: February 2023

A rigid spherical lap and rigid part in extended contact can only be spheres coincident to within the dimension of the intervening abrasive. Their only motion with respect to each while maintaining contact are their individual rotations. If the axes of these two rotations are noncoincident, they define a plane. If the axes are moving with respect to each other, this movement can be regarded as a rotational vector in a direction orthogonal to the plane defined by the two axes above, and this vector can be added to either of the two rotations described above or apportioned between them to define a reference frame. This demonstrates that at any moment there are actually only two independent rotations. For those familiar with vector algebra, the velocity of either sphere at any point on its surface can be described as the vector or cross product of its rotational vector with the radius vector of the point, i.e.
V→=ω→×R→. This discussion of the changing relationship between the rotational axes is also a precise description of a part stroked across a lap.
Submicroradian slope repeatability with the LTP
Authors: Takacs Peter Z. , Bresloff Cynthia J.
Published: February 2023

Modifications made to the Long Trace Profiler (LTP II) system at the Advanced Photon Source at Argonne National Laboratory have significantly improved the accuracy and repeatability of the instrument. The use of a Dove prism in the reference beam path corrects for phasing problems between mechanical errors and thermally-induced system errors. A single reference correction now completely removes both error signals from the measured surface profile. The addition of a precision air conditioner keeps the temperature in the metrology enclosure constant within + or - 0.1 degrees C over a 24-hour period and has significantly improved the stability and repeatability of the system. We illustrate the performance improvements with several sets of measurements. We are able to put an error bar of 0.3 microradian on a 500mm long surface. The improved environmental control has reduced thermal drift error to less than 1 microradian on a 500 mm long surface. The improved environmental control has reduced thermal drift error to less than 1 microradian RMS over a 7.5 hour time period. Measurements made in the forward scan direction and the reverse scan direction differ by less than 0.5 microradian RMS over a 500mm trace length. We are now able to put a 0.2 microradian error bar on an average of 10 measurements over a 200mm trace length. The corresponding height error bar for this measurement is 3.5 nm. We are now able to see systematic errors on the order of 1 microradian in magnitude that limit the ultimate accuracy of the instrument.
Minimizing tool marks in deterministic microgrinding
Authors: Li Yi , Gracewski Sheryl , Funkenbusch Paul , Ruckman Jeff
Published: February 2023

In deterministic microgrinding of glass optics with metal bonded diamond ring tools, optical surfaces exhibit residual cutting tool marks that can significantly affect the efficiency of the finish polishing process. The tool marks for spherical surface generation appear as curves that follow contact lines between the tool and workpiece from the center to the edge of the workpiece. The tool marks are circumferentially periodic and the number is typically equal to the k-ratio, i.e. the ratio of grinding tool speed to workpiece speed. This paper describes the effect of k-ratio, tool bevel size, tool vibration, tool roughness and their interaction on tool mark generation. We introduce a new parameter equal to the ratio of tool bevel size to the distance between two adjacent tool marks. Preliminary experimental results indicate that this ratio is the critical factor for tool mark generation. For ratios greater than a critical value, the amplitude of tool marks will be reduced to a level not detectable by interferometry. An analytic model is introduced, which describes the relations between surface quality and grinding parameters including part geometry, tool bevel size, tool speed, work speed, tool vibration amplitude and tool roughness. The model presented provides new insight into the generation of tool marks and optimization of deterministic microgrinding processes.
New Manufacturing Process of Prototype Plastic Lens with ELID (Electrolytic In-Process Dressing) Grinding
Authors: Moriyasu Sei , Nakagawa Takeo , Yamagata Yutaka , Ohmori Hitoshi
Published: February 2023

Nowadays many plastic lens are used in various optical systems, because the plastic lens can be mass-produced cheaply by the injection molding. But it is very difficult to produce a few plastic lens cheaply, because it requires much time and cost to make an injection mold. Turning is a way to make a few plastic lens directly and cheaply, but the plastic lens made by turning is not so good for optical lens, because the cutting marks give bad influence on optical characteristics of the plastic lens.
Software to link optical design and manufacturing
Authors: Sinclair Douglas C.
Published: February 2023

There has traditionally been a barrier between optical designers and fabricators that has impeded progress towards efficient overall engineering/production teams. The reason for the barrier is quite understandable: each group typically faces problems best solved by art rather than science. The fabricator is subject to the uncertainties that go along with processes that require highly skilled craftsmen, while the designer often does not know how the design works, or what the best tolerances are for a particular design. Current efforts to develop deterministic fabrication processes, along with increases in the computational power available to designers, hold promise of improving the situation and reducing the barrier between the two groups.
Using secure world-wide-web technologies to manage optics metrology data
Authors: Bradley Steven , Wheelock Everett
Published: February 2023

The Metrology Data Management System (MDMS) will simplify the collection and management of optics metrology data for the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL). During production the MDMS will be used to support the acceptance of optics, which requires that specifications have been met. The NIF assembly and operations groups will use the metrology data in MDMS to model and analyze NIF performance.
Scattering from normal incidence EUV optics
Authors: Gullikson E. , Stearns D. , Baker S. , Spiller E. , Bjorkholm J. , Taylor J.
Published: February 2023

The path to high resolution leads to shorter wavelengths. In the extreme ultraviolet (EUV) spectral region, imaging systems are possible using normal incidence reflective optics. As the diffraction limit is reduced, the errors in the optical surfaces often limit performance. Figure errors with a spatial period ranging from the size of the mirror down to about a tenth of the mirror size limit the resolution. Finish errors or roughness on a shorter length scale leads to non-specular scattering. Scattering will reduce the throughput of an optical system by removing light from the image. In addition, light scattered within the field of view (flare) can reduce the contrast of the image. For a lithographic imaging system this will reduce the process latitude. As the wavelength of light is reduced, the total integrated scatter increases as 1/λ2, which places a much more stringent demand on optical finish.
Improving Extreme-UV Lithography Camera Mirrors Using Deposition
Authors: Sweatt WC , Goeke RS , Warren ME , Tigges CP , Sommargren GE , Taylor JS
Published: February 2023

The Extreme-UV Lithography program requires aspheric mirrors that are superpolished and have an RMS figure accuracy of 0.1 to 0.3 nm. At present, neither requirement has been met on aspheric mirrors. We propose to achieve this accuracy by depositing a variable thickness coatings on precision superpolished mirrors. This is an extension of the work presented in the 1996 EUVL Topical Meeting (OSA TOPS Vol. IV, p. 149-151).
Technological Aspects of Deep Proton Lithography for the Fabrication of Micro-optical Elements for Optical Interconnects
Authors: Thienpont H. , Vynck P. , Tuteleers P. , Ottevaere H. , Baukens V. , Verschaffelt G. , Kufner S. , Kufner M. , Hermanne A. , Veretennicoff I.
Published: February 2023

The technology of deep proton lithography in PMMA (poly methyl methacrylate) is a fabrication method for monolithic integrated refractive micro-optical elements and micro-mechanical holder structures, which allows structural depths in the order of several hundred microns[1,2]. Different optical functions can be fabricated in one block and form monolithic integrated optical systems. In addition mechanical support structures and alignment features can be integrated with these optical systems. This paper will focus mainly on the technological requirements of the irradiation, development and diffusion setups, which are necessary to achieve predictable and reproducible results.
FAUST and WAGNER: generation of off-axis surfaces
Authors: Fähnle Oliver W. , van Brug Hedser , Frankena Hans J.
Published: February 2023

The generation of off-axis parts of rotationally symmetric surfaces applying FAUST and WAGNER is analyzed showing that there are often two fabrication processes possible.
Structural Effects In Thin Film Coatings
Authors: Hodgkinson Ian , Horowitz Flavio , Macleod Angus , Sikkens Marten , Wharton John
Published: February 2023

Four effects which depend on the columnar structure of thin films are discussed. The porous nature of many coatings permits atmospheric water to penetrate into the layers causing the refractive index to increase and the spectral profile to shift towards the red. In some cases the process is slowed or stops when a cover is cemented over the air-film surface. A narrow band interference filter with 'locked' patches (Fig.1) forms a suitable subject for the observation of scatter from absorbed water. To a first approximation the patches can be treated as a random array of identical sets of annular apertures, and the distribution of scattered light as the diffraction pattern of a single set of apertures.
Ion Beam Sputtered Anti-Reflection Coatings of Fused Silica Substrates
Authors: Perlmutter Michael S. , Martin Kenneth R.
Published: February 2023

A low reflectivity anti-reflection coating for use at 633 nm has been developed for fused silica substrates. The coating is a simple two layer design using silicon dioxide and titanium dioxide as the low and high index material. The thin films have been produced by ion beam sputtering techniques.
Monitoring for Periodic Multilayers by the Level Method
Authors: Puting Zhao
Published: February 2023

In optical coatings, one type of periodic multilayers is G((C1 A/2) (C2 B) (C1 A/2)) KM. Conventional interference edge filters are constructed when C1 = C2. The interference edge multilayers with unequal thickness are constructed when C1 ≠ C2. Such a multilayer system can be used as the narrow-band rejection filters, multi-frequency high reflectance coatings(1) and dichroic beam splitters. For the third case, both polarization effect and angular sensitivity are small when the light beam is incident with tilted angles. Therefore, its performance will be improved. Based on the literature(2), this paper describes a monitoring technology, the Level Method, which is suitable for monitoring periodic multilayers.
Implementation of a Large Thin Film Design Program on a Personal Computer
Authors: Bloom Arnold L.
Published: February 2023

A large thin film design and interpretation program, originally implemented on a large mainframe computer (IBM 3081), has been moved in its entirety to an IBM personal computer (IBMPC). This program, parts of which were discussed at the last Topical Meeting on Optical Interference Filters (1), includes features such as optimization with two different algorithms, statistical variation, electric field strengths, phase difference optimization, Herpin indices, monitoring, coating tank simulation and colorimetry.
LSM Technology Considerations for Extreme Ultraviolet
Authors: Keski-Kuha R. A. M.
Published: February 2023

All conventional coatings have low normal incidence reflectance in the soft x-ray and extreme ultraviolet spectral region. Recent studies however, have demonstrated that layered synthetic microstructures (LSMs)1-4 can provide soft x-ray and EUV mirrors with enhanced normal incidence reflectance. An LSM is a periodic multilayer thin film structure in which the refractive index varies periodically with depth. It is the analog of the quarter wave stack used for special coating designs in the optical region. In x-ray region where low absorption materials exist the ideal Bragg crystal geometry applies. EUV is a special region due to the increased absorption of all materials. Therefore, designs for maximum reflectance are obtained with a non-periodic stack to minimize absorption losses.
Thin Film Quarter Wave Retarders
Authors: Spiller Eberhard
Published: February 2023

Phase retarders and especially quarter wave plates are important components in an optical laboratory which have also found commercial applications in the optical disk. There have been previously reported attempts to replace the expensive crystalline quarter wave plate by dielectric thin film structures. Apfel1 showed that the phase retardation obtainable with periodic multilayer mirrors is less than 30°. Broad band multilayer mirrors with staggered thicknesses2,3 can produce much larger phase retardations; however, these phase retardations usually vary rapidly with wavelength or angle of incidence.
Ultra-microhardness Testing of Optical Coatings
Authors: Guenther Karl H. , Bangert H. , Kaminitschek A. , Wagendristel A.
Published: February 2023

The hardness of optical coatings is an important mechanical property, of particular interest if coatings are used under severe environmental conditions, such as encountered in military or ophthalmic applications. Hardness measurements are difficult to perform on optical coatings with standard microhardness testers which are used in connection with optical microscopes, since the minimal indentation loads of 0.5 to 2 g-wt (5 to 20 mN) cause imprints with penetration depths of about or even exceeding the coating thickness [1], thus measuring the hardness of the substrate rather than that of the coating. A Knoop diamond indentor with its pyramidal shape on a rhombic base (diagonal ratio 1:7) and an edge angle of 172°3′ causes a shallow penetration only 1/30 of the long diagonal deep. The more common Vickers pyramid (on a square base) with an edge angle of 148° has a penetration depth of 1/7 of the long diagonal. If the penetration depth in a thin film should not exceed 15-20% of its thickness in order to avoid the influence of the substrate hardness, the imprint diagonals range from about 0.06 μm downwards for the Vickers indentor and from about 0.25 μm down for the Knoop pyramid, e.g. for a single TiO2 quarterwave layer of 550 nm center wavelength. Such tiny marks can only be observed and measured in a scanning electron microscope (SEM). In earlier attemps to measure ultra-microhardness (UMH), the penetration depth of the indentor was measured directly with a capacitor bridge during indentation.[2], thus avoiding the need of a high magnification for measuring the imprint diagonals. However, this method may be incorrect because not only plastic deformation contributes to the result as defined for microhardness testing, but also elastic forces acting on the indentor tip.
Computer Controlled Spectrophotometer Measuring Reflectance and Transmittance Under Various Angles of Incidence
Authors: Hussmann Eckart K. , Becker Hans J.
Published: February 2023

A computer controlled filter spectrophotometer measures automatically reflectance and transmittance of interference coatings under various angles of incidence. Their properties can be evaluated.
Effects of Surface Quality on CO2 Optics
Authors: Rein Jerry
Published: February 2023

The purpose of this study is to give a practical understand ing of the effect of abnormalities found on various types of thin film coatings on different types of substrates used at 10.6 μm.
Determination of Optical Constants of Absorbing Films Reflectance and Transmittance Measurements
Authors: Botten L.C. , Netterfield R.P. , McPhedran R.C. , McKenzie D.R.
Published: February 2023

In many practical situations, it is important to know the optical constants (n and k) of thin absorbing films over a wide wavelength range. Knowledge of these optical constants enables the calculation of the interaction of electromagnetic radiation with the films when incorporated into devices such as heat mirrors, selective photothermal absorbers and photovoltaic cells. Less well known is the use of these constants in sum rules, in order to deduce bonding and structural information about the films [1,2].
Experiments in Thin Film Optimization Procedures
Authors: Goldstein Fred
Published: February 2023

In broad terms, optimization (minimization of a given starting function) procedures can be divided into two categories: those requiring derivatives and those requiring only the computation of the function to be minimized.1 For optical thin films, it appears that damped least squares (DLS) is the most widely used method requiring derivatives and simplex is the most popular non-derivative method.
Filter Design Considerations for the Visual Infrared Mapping Spectrometer of NASA’s Mars Observer Mission
Authors: Raouf Nasrat A , Duval James
Published: February 2023

Considerations for the design, fabrication and testing of 9 pass-band fitters deposited on two substrates to cover 0.30 to 5.54 μm range. These filters are used to separate different reflected orders of a diffraction grating.
Three Layer Approximation of Thin Film Systems
Authors: Skettrup T.
Published: February 2023

The replacement of quarterwave layers by two or three layers of two materials is common practice in the design of optical filters. The well known method of the Herpin equivalent layers has become a powerful tool for the thin film designer(1).
Theory, Design and Preparation of Metal-Dielectric Narrow-Band Spectral Filter Coatings Operating in Reflection
Authors: Gamble R. , Lissberger P. H.
Published: February 2023

The theory, design and preparation of narrow-band spectral filters operating in reflection will be described. Such filters consist of multilayers containing both dielectric and metallic films and are of particular interest for applications in fibre-optical communication systems in the wavelength region from 1250-1600 nm. In the theoretical discussion relationships will be developed which relate the potential transmittances of the main metallic film to important parameters of the filter, namely bandwidth and rejection; and it will be shown how the materials of the layers are chosen to meet these and other requirements such as free spectral range. Practical considerations, including the monitoring procedure, will be discussed; and the results of photometric observations on five filters will be presented and compared with theoretical predictions.
Structural Characteristics of Antireflective Diamond-Like Thin Films on Germanium
Authors: Vedovotto N. , Mackowski J.M. , Collardelle P.
Published: February 2023

Antireflective diamond-like carbon thin films have been deposited on germanium infrared windows using RF glow discharge technology. The C/Ge interface has been investigated through XPS and HRTEM, in order to settle whether a reactive interface is formed during the deposition process.
Searching for Super-Reflectance from a High Tc Superconductor Mirror Coating
Authors: Wei David T.
Published: February 2023

It is well known that a good conductor surface is also a good reflector. Classical theory1,2 has shown that the reflectance approaches unity as the resistivity approaches zero. However, such high reflectance has not been confirmed for high Tc superconductors from ultraviolet to far infrared3 although superconductive behaviors are detected in these materials at millimeter wavelengths4. It appears that imperfections on the material surface are still obscuring the super-reflectance. The intention of this paper is: (a) to show that reflectance of 100% is theoretically sound for high Tc superconductors, at least in the far infrared (FIR) region, and (b) to propose a reliable method of fabrication for producing super-reflecting mirrors.
Molecular Beam Deposited Bistable Interference Filters
Authors: Muirhead I T , Miller A , Lewis K L , Staromlynska J , Welford K
Published: February 2023

Ultra-high vacuum (UHV) and Molecular Beam Deposition (MBD) techniques have been used to fabricate ZnSe interference filters. These demonstrate optical bistability, with critical switching power being measured at five wavelengths between 521 and 676nm. These filters demonstrate considerably improved long-term operation stability over that offered by samples deposited using conventional thermal evaporation.
The Effect of Oxygen Incorporation on the Structure of Metal Fluoride Thin Films
Authors: Targove James D. , Lingg Linda J. , Lehan John P. , Macleod H. Angus
Published: February 2023

Ion-assisted deposition (IAD) has been widely studied as a means of improving the properties of optical thin films.1 Metal fluorides are a case in point, with MgF2 in particular being studied by several groups. Oxygen is a major impurity in IAD fluoride films; however, the nature of the oxygen incorporation has remained unresolved. In order to gain insight into the IAD process with metal fluorides, we have extensively studied the IAD of LaF3.2 A major advantage of LaF3 in this work is its highly crystalline nature, even when deposited onto ambient temperature substrates. Our results with LaF3 have clarified the nature of the oxygen incorporation in fluoride films. Identical results have been observed with CeF3 and NdF3 thin films, which are also highly crystalline.3 While we have also studied MgF2 and other low-index fluorides,3 the lack of x-ray diffraction peaks with these materials has prevented us from making similar direct observations; however, we expect the nature of the oxygen incorporation to be very similar for these materials.
Diamond Films - Optical Characterization and Applications
Authors: Messier R. , Vedam K. , Cong Y. , Yarbrough W.A. , Bachmann P.K.
Published: February 2023

Over the last three years the Materials Research Laboratory (MRL) at The Pennsylvania State University has had an active and expanding effort on the basic and applied science of diamond coatings prepared from the low pressure vapor phases [1,2,3].
Computational Studies of Status Profilometer Characteristics
Authors: Wilson S.R. , Al-Jumaily G.A. , McNeil J.R.
Published: February 2023

Stylus surface profiling instruments have found application in the characterization of microroughness. Al-Jumaily [1] has compared data obtained using a stylus profilometer and an optical scatterometer to characterize a metal surface. The stylus profilometer data was found to be inconsistent with the optical data. In resolving the discrepancy, the "transfer functions" of the instruments were identified as the source of the disagreement.
Characterization of Optical Coatings with Backscattering Spectrometry
Authors: Leavitt J. A. , McIntyre L. C. , Ashbaugh M. D. , Oder J. G.
Published: February 2023

Backscattering spectrometry,1 utilizing analysis beams of 4He ions in the energy range 1.5-5.0 MeV, is an underused technique for determining film thickness, stoichiometry, and impurity levels. The basic technique is illustrated in Figure 1. Analysis ions rebound from struck target (film) ions to impinge on the detector (subtends solid angle Ω) with energy characteristic of the mass of the struck particle; further, the He ions lose energy passing into and out of the film material. Energy analysis of the backscattered He ions from a film of uniform composition yields a nearly flat-topped "peak" for each element present in the film. The film elements may be identified by the energies (E1C, E1B) of the high-energy sides of the peaks. Areal density, (Nt)i, in atoms/cm2, may be determined for each element from knowledge of solid angle Ω, cross section σi, and integrated peak count Ai for Q incident analysis ions. Concentration variations appear as variations in the "flatness" of the peak tops. Note that the average stoichiometric ratio, Nc/Nb, depends only on the ratio of integrated peak counts, ac /a b , and knowledge of the scattering cross section ratio, σB/σC. Cross sections for scattering of 2 MeV 4He on all elements are nearly Rutherford (Coulomb's law holds), so Rutherford backscattering (RBS) is an absolute method that does not require the use of standards. Average stoichiometric ratios may be determined as accurately as 0.1% by acquisition of sufficient data, while areal densities are uncertain by about 3%. Conversion of areal density (in atoms/cm2) to physical film thickness (in Å) requires knowledge of film density. Conversely, if the physical thickness is known, areal density measurement will provide film density. Low-mass substrates (such as carbon) are preferred so that the substrate signal does not interfer with the film signals.
Stoichiometry of Reactively Evaporated Films
Authors: Feldman Albert , Farabaugh E. N. , Sun Y. N.
Published: February 2023

If an optical film is not fully oxidized, its refractive index will be different from fully oxidized material, and significant optical absorption may result. In order to ensure full oxidation of oxide films, evaporations are frequently carried out in reactive atmospheres containing significant partial pressures of oxygen. SiOx films provide a convenient system for studying the oxidation state of reactively evaporated films, not only because they are important coating materials,1 but because of structural models have been developed for this system. In this paper, the degree of oxidation of SiOx films, prepared by reactive electron-beam evaporation of Si under different partial pressures of oxygen, has been examined by x-ray photoelectron spectroscopy (XPS). The analysis suggests that the silicon in the films is not as fully oxidized as might be expected on the basis of the measured oxygen content.
Roughness Effects on Thin Metalic Film Surfaces Using Photoacoustic Spectroscopy
Authors: Machorro R. , Regalado E. , Siqueiros J. , Valenzuela J.
Published: February 2023

The influence of surface corrugations of a metal air boundary on the surface plasma oscilations (SPO) has been widely studied (refs. 1-4). Some conclusions are, a shift of the phase velocity towards smaller values and an increase of the damping of the SPO with increasing roughness. The quantification of this dependence has been carried out experimentally in several laboratories, mainly by the use of ATR techniques. Photoacoustic spectroscopy is an alternative technique that has been succesfully used and has shown to be more more general and as sensitive as ATR.
Fabrication and Testing of Large Area Multilayer Coated X-ray Optics
Authors: Spiller Eberhard , Golub Leon
Published: February 2023

As a part of our ongoing program for the production and testing of multilayer coated soft x-ray optics, we have performed a series of experiments designed to produce useable large area mirrors. In particular, our immediate efforts have been driven by the goal of producing a 25cm diameter Ritchey- Chretien telescope for use in imaging of the Solar corona. However, it is clear that large area mirrors are desireable in other fields and the techniques which we discuss are useful whenever such coated, figured surfaces are needed.
Short Wavelength Coatings for Large Optics
Authors: Kurdock J. , Strouse E. , Tirri B.
Published: February 2023

The application of X-ray and VUV coatings on large optics pose unique problems for the coating engineer. Facility design, process development, and characterization will be discussed for several applications.
Codeposition of Continuous Composition Rugate Filters
Authors: Gunning W. , Hall R. , Woodberry F. , Southwell W.
Published: February 2023

Sinusoidal refractive index profile filters (rugates) are ideally monolithic structures, having no interfaces between dissimilar materials. This is expected to avoid the stress and delamination problems which often arise in thick multilayer thin film filters. The sinewave refractive index profile demonstrates a significant suppression of higher frequency reflective sidebands. Furthermore, multiple, independently selectable reflection bands can be obtained by a superposition of sinewaves of appropriate period. This is demonstrated in Fig.1.
Rugate Index Profile Which Suppresses all Harmonic Stopbands
Authors: Southwell W.H.
Published: February 2023

In the literature, several multilayer coating configurations have been proposed which have a reflectance stop band at the tuned wavelength and for which various orders of harmonic stopbands have been suppressed. Baumeister 1,2 has outlined a procedure for designing a symmetric multilayer in which any number of higher order harmonic stopbands are suppressed. He makes the statement that, "As more and more contiguous stopbands are suppressed, the stepped-index profile approximates a sinusoid." However, the algebraic complexities of his approach make it difficult to determine the index profile as it approaches the continuous limit. Prior to this, Thelen3 published plots of the equivalent index for an inhomogeneous system where the index varies with the Jacobian elliptic function4 dn. Recently, Carniglia5 showed that stepped-index designs in which the natural log of the index follows a sinusoid will have good harmonic suppression out to a certain order. (This log index sinusoid dependence we call an exponential sinusoid in this paper, since that is how the index itself varies.)
Rugate Side Lobe Suppression Using Quintics and Rugated Quintic Matching Layers
Authors: Southwell W.H.
Published: February 2023

It is shown that quarterwave matching layers are effective in suppressing rugate side lobes only near the wavelengths for which the matching layers are quarterwave. Quintic matching layers (which are fifth-order polynomial index variations with zero first and second derivatives at each end), on the other hand, are capable of suppressing side lobes over wide wavelength regions. Furthermore, the OD loss due to the index matching can be largely restored by the superposition of rugate cycles on the quintic matching regions. It is also shown that the entire rugate may be impressed upon thick quintics. Such structures have excellent broadband side lobe suppression.
Inhomogeneous Layers Revisited
Authors: Abeles F.
Published: February 2023

We shall examine : cermets (metal-dielectric mixtures) which in many respects behave like homogeneous effective media and stratified in-homogeneous media characterized by a dielectric function Σ (z).
Optical Characterization of Thin Films by Guided Waves
Authors: Pelletier E.
Published: February 2023

The study of guided waves in a thin layer allows a precise characterization of refractive index and thickness. Optical anisotropy can also be measured. We show how this technique can be applied to the characterization of a multilayer structure.
Analytical determination of the complex refractive index of an opaque film deposited on a transparent substrate from the pseudo-Brewster angles of internal and external reflection
Authors: Azzam R. M. A.
Published: February 2023

A new method is described for the explicit determination of the refractive index amd extinction coefficient of an opaque film deposited on a transparent substrate from purely angular, nonpolarimetric, measurements. In particular it is shown that the real and imaginary parts of the complex dielectric constant ε = εr –j εi of the film are obtained analytically, directly and noniteratively, from the pseudo-Brewster angles (PBAs) of internal and external reflection. This follows from a study of the properties of the contours of constant PBA in the complex ε plane. For this method to be accurate, one of the two PBAs should be <45°, i.e. the substrate should be sufficiently optically dense or the UV and VUV spectral range is of interest. Experimental errors of the PBAs may also render impossible the determination of εi when |εi/εr|≪1. Simulated measurements on Ag and TiN films will be presented to demonstrate the method.
Determination of Optical Constants by Angle-Scanning Reflectometry
Authors: Deeter Merritt N. , Sarid Dror
Published: February 2023

Accurate characterization of optical constants of metal films is often prevented by unwanted overlayers which may be due to oxidation, surface roughness, or other causes1. These overlayers in general have different optical characteristics than the underlying metal film and thus can significantly alter the optical measurements (e.g. reflectance or ellipsometry) made on the sample. Ignoring these overlayers generally leads to inaccurate estimates of the actual optical constants of the metal. To avoid this problem, the overlayer must either be eliminated or included as part of the theoretical model. Unfortunately, inclusion of the overlayer in the model introduces more unknowns to be determined, and makes data analysis considerably more complicated. A more simple approach, which we employ, is to make the optical measurements through the (transparent) substrate. In this case, the radiation interacts only with the unexposed portion of the metal film (assuming the film is sufficiently thick) and hence surface oxide or roughness layers do not affect the optical measurements.
From light scattering to the microstructure of thin film multilayers
Authors: Amra C.
Published: February 2023

Light scattering from optical coatings takes its origins in the structural irregularities at interfaces and in the bulk of materials in thin film form. For this it carries information relative to the materials microstructure and may constitute a powerful tool for characterization. However this information is not easy to extract because of the complex relations that connect the scattered light to the microstructural parameters of the stack. This is one kind of inverse problem involving numerous parameters while we have only few equations given by the measurements. Our efforts have continued in Marseilles in this field and we will point out the level of understanding that has been reached.
Comparison of surface and bulk scattering in optical coatings
Authors: Amra C. , Bruel L. , Grèzes-Besset C.
Published: February 2023

In many cases it was shown that light scattering from optical coatings takes its origins in the interface irregularities of the stacks. This result is mainly due to a "substrate effect", consisting in the reproduction of the initial surface at each interface of the multilayer [1]. However the improvement of polishing techniques permits today to obtain substrate roughnesses less than 0.1 nm for certain materials; in these conditions the substrate effect is largely reduced and intrinsic properties of the thin film materials may be studied. The residual light scattering from these high quality filters originates from random irregularities characteristic of the materials and may be present in their bulk or still at their interfaces. Therefore an accurate characterization of materials requires to have at our disposal an adequate tool that enables to display the origin of scattering (surface or bulk) in the stacks. For this we use vector theories of surface and bulk whose basic principles will be briefly described. Numerical calculation then permits to emphasize the essential differencies between these two phenomena and the conclusions permit to choose the right experiments to realize. In other words, can we use wavelength, incidence or polarization to detect the origin of scattering? Is there any particular stack more adequate for this study? What is the relative amount of surface and bulk scattering? All these points will be clearly discussed.
Reflection of Electromagnetic Waves from a Surface with a Low Relief
Authors: Vitlina R.Z. , Dykhne A. M.
Published: February 2023

The effective permittivity tensor of a layer with surface roughness is calculated by solving the electrostatic problem analytically and numerically.
A Status Report on the Development of International Standards for Optical Coatings
Authors: Boultbee Gordon , Clover Jane
Published: February 2023

A working group of the International Standards Organization Technical Committee for Optics and Optical Instruments has been preparing a standard for the specification, measurement and test of optical coatings. The new standard could supersede the variety of US military, ANSI, DIN and other specifications now used. The work has progressed to the point where it shortly will be circulated for comment by interested parties. The purpose of this paper is to inform those involved in the use and manufacture of optical coatings of the existence of this draft standard and to encourage comment on its form and content.
Intrinsic Stress in Sputter Deposited Thin Films
Authors: Windischmann Henry
Published: February 2023

A review of the sputtered film stress literature shows that the intrinsic stress can be be tensile or compressive depending on the energetics of the deposition process. Modeling studies of film growth and extensive experimental evidence shows a direct link between the energetics of the deposition process and film microstructure, which in turn determines the nature and magnitude of the stress. The fundamental quantities are the particle flux and energy striking the condensing film, which are a function of many process parameters such as: pressure, target/sputtering gas mass ratio, cathode shape, bias voltage, substrate orientation. Tensile stress are generally observed in Zone 1 type, porous films and are explained in terms of the grain boundary relaxation model while compressive stress, observed in Zone T type, dense films, is interpreted in terms of the atomic peening mechanism. Modeling of the atomic peening mechanism and experimental data indicate that the normalized momentum may be the appropriate stress scaling factor in the compressive stress regime. An idealized stress momentum curve is constructed depicting the three characteristic stress regions. The precipitous tensile-to-compressive stress transition often observed in sputtered films may be associated with a threshold energy transfer phenomenon, occurring at approximately the atomic displacement energy.
Measurements of Spectral Shifts and Stress Versus Relative Humidity in Multilayer Coatings
Authors: Pond B.J. , Nusbaum H. , Du T.C. , Sobczak J. , Schmell R.A. , Carniglia C.K. , Petty R. , Johnston J. , Charlton G.B.
Published: February 2023

The spectral performance of most multilayer optical coatings varies with changes in relative humidity (RH). The production of humidity-stable coatings is important to many applications where spectral performance is critical. An example of such an application is dichroic filters for multiple wavelength fiber-optic communication systems.
Electrochromic Thin Films
Authors: Granqvist C.-G.
Published: February 2023

Basic physical and electrochemical properties of electrochromic thin films are discussed, with emphasis on tungsten-oxide-based materials. Applications of these films in several types of electrochromic devices are outlined.
Laser Mirrors with Variable Reflected Intensity and Uniform Phase Shift
Authors: Piegari Angela , Emiliani Gabriele
Published: February 2023

For some years the employment of coatings with radially variable reflectance in laser resonators has been gradually increasing. In fact mirrors with gaussian or supergaussian profiles of the reflected intensity, used as output coupler of unstable laser resonators, give diffraction limited laser beams with high energy or power.
Finite-Difference Time-Domain Modeling of Electric-Field Enhancement at Nodular Defects in Dielectric Mirror Coatings†
Authors: DeFord J. F. , Kozlowski M. R. , Shang C. C.
Published: February 2023

At LLNL we are interested in increasing the damage threshold of optical coatings used in high power laser applications such as Inertial Confinement Fusion. The coating of particular interest is a highly reflective dielectric multilayer mirror (HR) consisting of many alternating quarter-wave layers of HfO2 and SiO2 at 1.06μm. Laser induced damage in optical coatings is often associated with structural defects in the films. In dielectric HR coatings the predominant surface defects are μm-scale domes associated with the classic nodule defect. The nodule shape is determined by shadowing effects during the deposition process and can originate at a seed either at the substrate surface of within the film itself. Recent results using Atomic Force Microscopy and conventional Nomarsky microscopy [1] have shown that the nodule defects also control the laser conditioning effect in which the damage threshold of multilayer dielectrics can be increased by factors of 2-3 by post-deposition subthreshold illumination [2].
Optical Multilayer Coatings Deposited by Ion-Plating
Authors: Waldorf Allan J. , Dobrowolski J. A. , Sullivan Brian T.
Published: February 2023

Materials deposited by reactive ion-plating have excellent adhesion and abrasion resistance along with high refractive indices due to their dense microstructure and, therefore, are ideal for optical multilayer coatings. Numerous coatings deposited by ion-plating have been produced and their optical properties measured.1,2 In general, the coatings have good laser damage thresholds, although for some materials they are still lower than those of e-beam deposited coatings.3 Other advantages of ion-plated coatings include low surface roughness and low or zero porosity and, hence, good stability.