bluuebunny/crossref_metadata_2025 huggingface dataset:
X-Ray Tests of Multilayer Coated Optics
Authors: Golub L. , Spiller E. , Bartlett R. J. , Hockaday M. , Kania D. R. , Trela W. J.
Published: February 2023

The development of new XUV and x-ray optics has important applications in a wide variety of scientific fields, including x-ray astronomy, laboratory plasma diagnostics, and synchrotron radiation instrumentation. We are presently involved in ongoing research programs in soft x-ray imaging of astrophysical sources; in this context, the important design goals of imaging optics are both spatially resolved dispersive spectroscopy as well as very high angular resolution imaging in and of itself. Typical state-of-the-art soft x-ray imaging using grazing incidence optics can attain angular resolution of order 0.5 seconds of arc. With the kind of instrumentation here envisaged, it appears that an order of magnitude improvement is feasible immediately [1] and attainment of .01-.005 seconds of arc seems to be within reach.
Laser Coatings
Authors: Ebert Johannes
Published: February 2023

This paper reviews various methods of application of ion beam sources for the production of low-loss laser coatings. Ion beams can be used to sputter a target material to be deposited on a substrate and the beams can be directed to the deposited films to change their chemical and physical properties. Four deposition methods were compared:

- Electron beam deposition - Ion assisted deposition -

- Ion beam sputtering - Dual beam deposition -

In the production of high quality laser coatings it is extremely important to prevent the decomposition of evaporation materials. These coatings should be deposited stoi-chiometrically as traces of metals or metal suboxides cause absorption losses. Especially coatings for laser applications should have no ansorption losses. Losses reduce the reflectivity and lower the damage threshold for high power radiation.
Design of High Power Laser Polarizer for Multiwavelength Operation
Authors: Monga J.C. , Gupta P.D. , Bhawalkar D.D.
Published: February 2023

Laser plasma interaction studies and the requirements to drive inertial confinement fusion targets at ever higher powers and energies has helped accelerate the development of high power, short pulse, glass laser systems at various laboratories [1]. An important requirement in the development of these laser systems has been the availability of high, power resistant, large aperture polarizers. Dobrowolski et. al. [2] have given the design of a liquid prism polarizer for use with high power excimer lasers thereby overcoming the inherent limitations of the conventional polarizers. Several other authors [3-6] have given different designs of multilayer stacks and their combinations to achieve the desired polarizational properties. These polarizers [3-6] are however designed for a particular wavelength and thus have a very limited bandwidth which can be increased only to a limited extent by increasing the refractive index ratio of the materials. More recently, there has been a considerable interest in using shorter wavelength lasers as a possible fusion driver mainly because of increased absorption efficiency [7]. The existing Nd: glass lasers are being frequency multiplied [8,9] and new laser systems like excimer lasers are being developed [10]. It therefore becomes desirable to have optical components that could be interchangeably used for different wavelengths. In this paper, we report the design of a multiwavelength polarizer simultaneously working at the fundamental and second harmonic of Nd: glass laser. The desired polarizational properties are achieved by suitably combining two or more multilayer stacks with appropriately adjusted thicknesses.
Coatings for Photolithography
Authors: Hagenlocher Arno K.
Published: February 2023

Microlithography is used to transfer a geometrical pattern from a mask to a substrate. The principle of the process is similar to any imaging method. A source emits radiation which may consist of photons, electrons, or ions. An object represented by a layout on a mask will be imaged by an optical system to a receptor called a photoresist. The radiation will change the chemical bindings of the resist. The pattern generated in the photoresist is then transferred to the underlying substrate which in the case of semiconductor manufacturing is usually a wafer of silicon. The resolution limit for lithography is determined by the optical system, the photochemistry of the resist, and the transfer process to the substrate. This paper will cover only the optical part of this topic.
How is Optical Scattering Related to the Microstructure and Topography of Thin Films?
Authors: Bennett Jean M. , Guenther Karl H.
Published: February 2023

In predicting the reflectance, transmittance, and other optical properties of film-covered substrates, the films are usually modeled as uniform, plane parallel layers having constant (complex) refractive indices. However, it is well known that film structure is strongly influenced by the condition of the substrate onto which it is deposited. Optical scattering theories modify the above zero order assumptions by introducing microroughness on the substrate and film surfaces. In first order scattering theories the heights of surface microirregularities are assumed to be much less than the wavelength of light. In order to calculate the angular dependence of the scattered light,1 it is necessary to know the statistical properties of the microroughness, specifically the autocovariance function or its Fourier transform, the spectral density function. Recent experiments2,3 have shown that in some cases this information is not enough to correctly predict the complete angular scattering distribution; more detailed modeling of the film structure is needed. In order to better relate optical scattering of thin films to their structural and topographic features, we have made electron micrographs of replicas of film surfaces and their cross sections, and microtopographic measurements on films and bare substrates using a stylus-type profiling instrument having a lateral resolution ~ 0.1 to 0.2 μm. We have also obtained surface profiles from an analysis of microdensitometer traces of electron micrographs of surface replicas.4 Films studied include silver and multilayer dielectric stacks deposited onto microscope slides, fused quartz, and Zerodur substrates. When silver films are baked in vacuum, appreciable differences are observed in film structure, and large differences are also observed in the total scattering and its angular dependence. Measured scattering from various film-substrate combinations whose microstructural features have also been measured will be compared with theoretically predicted values. Further modifications to the theory have been proposed5 in order to better incorporate observed film microstructure into vector scattering theory.
The Hadley-Dennison Equations Revisited, Accompanied by Newton
Authors: Barnes A. H. , Hadley L. N.
Published: February 2023

We have re-examined the equations(1,2) relating the reflectance R and the transmittance T to the optical constants n and k, and the ratio of thickness to wavelength s/λ. One typically measures values of R and T and s/λ, and would like to know the associated optical constants. One method so far has been to resort to the plotted values of R and T as a function of s/λ for various values of the parameters n and k.
Design of a Vanadium Dioxide Switchable Coating
Authors: Macleod H. A. , Case W. E. , Purvis M. K.
Published: February 2023

Vanadium dioxide undergoes a thermally induced, first-order phase transition from semiconductor to metal near 67°C. It has been investigated in thin-film form for a number of applications1 as a material that can be switched between two optical states using laser2 and electron beam3 sources. Unfortunately, requirements on optical performance often preclude a simple structure of thin-film vanadium dioxide deposited on a massive substrate.
A study of Lead Telluride Optical Coatings
Authors: Ling-xin Zhu , Yi-hsun Yen , Wen-de Zhang , Feng-shan Zhang , Shou-ying Wang
Published: February 2023

Lead telluride is one of the important infrared high refractive index coating materials beyond 3.8 microns. Because of the great difference in vapor pressuse between lead and tellurium, in a deposited PbTe layer more Te will be lost. Conventionally, evaporable PbTe is prepared from stoichiometric proportions of pure constituents. From the phase diagram of Te and Pb it is obvious that the resulting material is always a p-type semiconductor. In using the conventionally prepared material to deposit coatings even at a rather low substrate temperature of, say, 100°C, a strong n-type PbTe layer is formed, which will lead to a strong free carrier absorption. As the substrate temperature is increased even more free carriers will be introduced. In order to obtain a PbTe layer of good quality a compensative process is required. This has been realized by O2 bombardment during deposition or by baking in the air after deposition.(1)(2) In addition, a n-type PbTe layer is less stable. In certain conditions it can be compensated either by O2 or by S and Se. The latter is just the case of preparing multilayer coatings, in which case the refractive index and absorption of a fresh PbTe layer will be shifted and hence the accuracy of optical thickness mornitoring will be reduced.(3)(4)
Design of High Rejection Filters by the Inverse Fourier Transform Method
Authors: Verly P.G. , Dobrowolski J.A. , Wild W.J. , Burton R.L.
Published: February 2023

There is a growing need for narrow tend high rejection filters. Such filters can be designed to consist of multilayers composed of many homogenous films, or of a single thick inhomogeneous layer.
Modified Mac Neille Cube Polariser for a Wide Angular Field
Authors: Mouchart J. , Begel J. , Duda E.
Published: February 2023

Some well known relations between thicknesses and indices of a stack of optical layers allow to obtain very good polarisers of light. One of the most famous is the Mac Nellie cube polariser. In this case one of the hypotenuse face of two isosceles right angled prism is coated with a polarizing deposit, and then cemented to the other hypotenuse face, This polariser can be used on a large spectral range located in the s vibration stop band, Unfortunately the insertion losses for the p vibration are important when the angular field is larger than ± 2 degres.
Infrared Coatings
Authors: Dobler Hermann R.
Published: February 2023

IR Coatings are optical interference coatings used for at least one of the atmospheric windows from 3-5 or from 8-12 microns. Particulary interesting are coatings which are additionally used for the visible spectrum, or high power coatings for the CO2-laser at 10.6 microns. The main applications of IRCs are thermal imagers and laser systems. Some special topics concerning IRCs, which differ from other types of coatings, are discussed.
Comparison Between Classical and Ion Assisted Deposited TiO2 Layers for Optical Coatings
Authors: Lottiaux M. , Boulesteix C. , Varnier F. , Flory F. , Pelletier E.
Published: February 2023

The Electron Microscopy shows that the observed microstructure of titania films produced by Ion Assisted Deposition strongly differs from that of films produced by classical evaporation.
Surface Optical Coatings by Ion Assisted Deposition Techniques: Study of Uniformity
Authors: Flory F. , Pelletier E. , Albrand G.
Published: February 2023

Uniformity of layers produced by I. A. D. strongly depends on the characteristics of the ion beam: optical characterization is made by guided wave measurements.
Complex-Grid Ion-Source and Ion-Beam-Assisted Deposition of the Films
Authors: Xing-Yi Chen
Published: February 2023

The work reported here is an investigation of the construction and propeties of a complex-grid ion-source. The operation of such a source is also described. Using an ion-beam-assisted deposition process with our complex-grid ion-source, we have manufactured some high quality films.
Stress reduction in ion beam sputtered films
Authors: Pond B.J. , DeBar J.I. , Carniglia C.K. , Raj T.
Published: February 2023

Thin film optical coatings made by ion beam sputter deposition (IBSD) have excellent optical properties, such as high refractive index, low absorption and low scatter. In addition, IBSD films can be produced without applying external heat to the substrates. These properties make IBSD coatings suitable for low-loss applications, such as ring laser gyroscope mirrors and resonator mirrors in high-energy lasers.1 One limitation of these coatings is that the materials have a high compressive stress which can significantly distort an optic coated with a thick multilayer IBSD coating.2 Several techniques have been demonstrated for modifiying the intrinsic stress in thin films, including ion bombardment of the growing film, altering deposition parameters and combining two materials by coevaporation or cosputtering.3
Sputtering of Metal Oxides with an rf-Ion Source
Authors: Kessler Ingo , Mueller Juergen , Steiniger Gerhard
Published: February 2023

Ion beam of relatively low energy and large area have become a valueable tool in thin film production. The energies for the most important processes are several ten to several hundered eV for etching and ion assisted evaporation and several thousand eV for sputtering.
Improvement of abrasion resistance of SiO2/TiO2 multilayer interference filters
Authors: Taga Yasunori , Itoh Tadayoshi
Published: February 2023

Progress has been made in the development and practical applications of various types of multilayer interference filters (1). Among them, infrared reflection filters(IRF) are strongly expected to be widely used as a solar radiation shielding on the window glass of automibiles(2)-(5). However, it has been impossible to apply the multilayer interference coatings to the window glass of automobiles or buildings because of their lack of sufficient abrasion resistance. In order to improve the abrasion resistance, the multilayer stacks were usually subjected to heat treatment at high temperature of around 500°C-600°C or more. Such high-temperature heat treatment, however, could not be appliciable to the window glass of automobiles.
Optical properties of coatings prepared from laser fused refractory oxide mixtures
Authors: Mallavarapu Swarnalatha , Stewart Alan F. , Guenther Arthur H. , Raj Tilak , Carniglia C. K.
Published: February 2023

Inhomogeneity and a lack of reproducibility in optical thin film coatings has been attributed in part to chemical decomposition and phase transitions which may occur during exposure to the high temperatures frequently present during deposition. A stable material which does not exhibit phase transitions or decomposition could significantly improve the reproducibility of thin film fabrication. Potentially large groups of materials which fit these requirements exist as ceramics and as solid solutions formed from combinations of many common refractory oxide materials. The combination of ZrO2, HfO2 and Y2O3 has been shown to form a solid solution with a stable crystalline phase at high temperatures.1 In the present investigation, we have studied the properties of optical thin films deposited from solid solutions of these materials of varying compositions. Analysis of these coatings indicates that generally improved optical films can be obtained using solid solution mixtures in comparison to films deposited from single component starting materials.
Layer Uniformity Obtained by Vacuum Evaporation. Application to Fabry-Perot Filters
Authors: Grèzes-Besset C. , Richier R. , Pelletier E.
Published: February 2023

We show how we can measure with accuracy the uniformity of layer thickness for different materials obtained by vacuum deposition. Generalization to multilayer stacks raises many difficulties due to time dependence of evaporant distribution.
Application of Neutral Ion Beams to Optical Substrate Fabrication
Authors: Wilson S.R. , McNeil J.R.
Published: February 2023

Ion beam sputtering has emerged as a viable means of removing material from an optical surface. Ion beam sputtering was first used as an optical figuring technique in the mid 1960’s [1,2]. Since that time, a number of investigators have applied ion beam sputtering as a fabrication technique, with some degree of success. However, these early efforts were severely limited by the availability of suitable ion sources. The ion sources were typically low correct (fraction of a milliampere), high energy (20KeV to a fraction of an MeV) ion sources, with a very narrow beam, usually a millimeter or less in diameter. The low beam current produced low material removal rate, while the high beam energy was often found to induce mechanical, radiation, or chemical damage in the surface.
Shape and substrate effects on the optical absorbance of metal-spheroidal island coatings
Authors: Goudonnet J.P.
Published: February 2023

Condensation of metal vapors onto substrates does not produce microscopically uniform thin films. Rather, thin (less than 20 nm) films of many materials appear to grow from nucleation points, producing islands, so that electrical conductivity is disturbed. Anomalous optical behavior of such films results. Extensive investigations of gold and silver films have been performed(1) with the conclusion that simple application of the three-dimensional Maxwell Garnett(2) theory is inadequate to describe the response of the films. A more sophisticated theory replaced the spherical particles of the Maxwell Garnett theory by spheroids, considerably improving agreement with experiment.
Effects of Metal Coatings on the Surface Roughness and Optical Scatter Characteristics of Coated Surfaces
Authors: Al-Jumaily Ghanim , Wilson S. R. , Jacobson R. D. , McNeil J. R.
Published: February 2023

Optical scatter is an important property to consider in optical coatings. Although an undesirable effect, optical scatter can be used to characterize surface microroughness. It is normally believed that coatings increase surface roughness, or at best replicate the surface microstructure. We have found that this is not always the case. At the previous OIC meeting we introduced this investigation, and for the last few years we have been examining this effect in more detail. The microroughness of coated surfaces can increase or decrease as a result of coatings. In this paper we review the process of surface smoothing and its dependence on coating process, film properties and initial surface conditions.
Scattering Study of Single Layer Titania Films
Authors: Hickey C. , Amra C. , Pelletier E.
Published: February 2023

Light scattering measurements further characterize a series of TiO2 thin film samples. Previous analyses were given at the 1986 and 1987 O.S.A. annual meetings.
The Crystallographic Transition in Conventional Bronze and Anomalous Blue VO2 Thin Films
Authors: Case Francine C.
Published: February 2023

Thin films of vanadium dioxide exhibit a thermally induced semiconductor-to-metal phase transition near 67°C.1,2,3 Below 67°C the material is a semiconductor with a monoclinic structure. Above 67°C it becomes metallic, transforming to a higher symmetry tetragonal structure. Conventionally deposited films display large changes in optical properties in the infrared spectral region; however, not much contrast is observed at visible wavelengths.4 They are bronze in transmission and do not change color appreciably when heated. The microstructure consists of tightly packed coherent grains ranging from 0.1 to 0.5 microns in diameter, depending on deposition conditions.
Thin Film Microstructure Effects on Ellipsometric Thin Film Deposition Monitoring
Authors: Gunning W. , Moyle J.
Published: February 2023

Ellipsometry is increasingly finding application to real time monitoring of thin film deposition.1 This has been accelerated by the availability of commercial automated instruments which are specifically designed for vacuum system installation. While the ellipsometer can be quite accurate, it is affected by a number of effects arising from the nonideal morphology of most thin films. In particular, refractive index inhomogeneities and polarization effects result from scattering and form birefringence produced by columnar microstructure. Modeling of these effects demonstrates that form birefringence has the greatest effect on ellipsometric accuracy.2
Wide-Band Optical Monitoring of Broad Band AR Coatings*
Authors: Xue-Qun Hu , Yu-Ming Chen , Jin-Fa Tang
Published: February 2023

It is well known that the wide-band monitoring method /1//2/ is advantageous to construction of multilayers with optical properties that are specified over an extended wavelength region.
An Overview of Rugate Filter Technology
Authors: Johnson Walter E. , Crane Robert L.
Published: February 2023

Rugate filters are examined from historical and current research perspectives. Design features important to optical system usage are covered.
Spectroellipsometry of Thin Films
Authors: Aspnes D. E.
Published: February 2023

Thicknesses, compositions, microstructures, and densities are among the properties that can be nondestructively determined from spectroellipsometric data on thin films. The current status is reviewed.
Determination of Principal Refractive Indices of Birefringent Thin Films
Authors: Horowitz F. , Macleod H. A.
Published: February 2023

Discriminatory optical behavior of obliquely deposited films with respect to the polarization of light has been known for about a century.1 Although scarce, reports on this effect can be found in the literature from the early2-5 and mid6-8 1900's. More recently, metal films were used as polarizers in the near-infrared9 and dielectric films were shown to perform as phase-retarders in the visible.10 Those are two different manifestations of structure-induced optical anisotropy in connection with significant asymmetries in extinction coefficient and refractive index valves, respectively.10
Optical Constant Determination of Magneto-optical Thin Film Using Surface Plasmon Resonance Phenomenon
Authors: Mao Y. , Macleod H.A. , Balasubramanian K.
Published: February 2023

Recent research identifies amorphous rare-earth-transition-metal thin films as most promising magneto-optical (MO) erasable storage materials. While writing is achieved by thermomagnetic means, reading is performed using polar Kerr magneto-optic effects. Generally the polar Kerr effect of MO films is quite small, being a fraction of a degree in rotation of polarization. Multiple dielectric protective layers can also enhance the magneto-optic Kerr effect [1,2]. The refractive index n and extinction coefficient k are required for the design of multilayer structures but little data exists for magneto-optical materials. We developed a method to measure the optical constants using the surface plasmon resonance phenomenon, which is based on the high sensitivity of that resonance to the optical constants [3,4], The configuration is shown in Fig.l. Light polarized with electric field parallel to the plane of incidence (TM) is incident within the glass upon the inside surface of the MO thin film. At angles of incidence greater than the critical angle for total reflection, an evanescent wave penetrates the metal and excites the natural modes of oscillation of the density of electrons at the surface of the MO film. At certain angle of incidence such that the component of the optical wave vector parallel to the metal surface is equal to the wave vector of the surface plasma wave, resonant coupling occurs for a properly chosen thickness of the film. Since, because the angle of incidence is beyond the critical angle, no wave propagates into the third medium (air), surface plasma waves are detected by noting the deep minimum in the internal reflectance. Fig. 1 shows diagramatically the arrangement of its apparatus.
Refractive Index Determination using an Orthogonalized Dispersion Equation
Authors: Carniglia C. K. , Schrader K. N. , O'Connell P. A. , Tuenge S. R.
Published: February 2023

The refractive index n and thickness t of a thin-film coating can be determined from ellipsometric measurements of light reflected from the film. If data are taken over a broad range of wavelengths, then a range of values of n and t are obtained. The variation in n is expected and is a measure of the dispersion of the material. The variation in t, which is often found, results from the failure of a single-layer model to explain the measured data. This may occur because the film is inhomogeneous or anisotropic.
A Simplified Description of Light Scattered by an Optical Coating
Authors: Apfel Joseph H.
Published: February 2023

An ideal optical coating applied to an ideal surface will control the intensity and phase of an optical ray in reflection, transmission and absorption without affecting its direction of propagation. Real optical coatings deposited on substrates with imperfect surfaces scatter radiation away from the specular direction. The scattering of light in a multilayer is caused by defects, inhomogeneities, and roughness of the interfaces between the layers. Defects include particles of foreign materials or voids which are embedded in the structure. Inhomogeneities include local variations in the density, and thus the refractive index of a layer. Although defects and inhomogeneities may be treated theoretically, there is more to be gained by their elimination through careful manufacturing techniques than by understanding their contribution to scattering. The roughness of interfaces in multilayers is difficult to control and survives the most gallant experimental efforts. The theoretical treatments of scattering by optical coatings predict the spectral and angular content of scattered light as functions of the deviations of the interfaces from perfect planes.
In-Situ Measurements of the Stability of Conventionally Evaporated and Ion-Assisted Deposited Narrowband Filters
Authors: Rudigier H. , Schöch H.
Published: February 2023

Results of a comparison of the stability of conventionally evaporated and ion-assisted deposited narrowband filters as a function of deposition parameters are presented.
Testing of Erosion Resistant Infrared Coatings by Nanoindention Techniques
Authors: Barron A. , Slomba A. , VanMilligen F. , Abouelliel M. , Conopask L. , Eaton H. , Nighan W.
Published: February 2023

Erosion resistant infrared coatings are critical aspects of next generation avionic sensor windows. Current testing techniques employing water jets and particulate impacts and qualitative measurements which are very difficult to relate to the physical parameters of the optical coating. For future improvements in this area, investigations have been undertaken to relate these destructive tests to properties of hardness, elasticity and adhesion as measured using nanoindention techniques. The goal of this effort is to develop strong enough correlations between quantitative physical characteristics and the qualitative erosion testing to allow more rational approaches to coating improvements with respect to its rain and particle erosion resistance characteristics. It is hoped that these tests may result in less destructive acceptance test for the avionic windows. It should be noted that the information gained during this effort is unique and the first of its kind as applied to infrared erosion resistant coatings. This paper presents preliminary results of this on-going effort.
Spectral Filters Based on Principles Other Than Interference of Light in Thin Films
Authors: Dobrowolski J. A.
Published: February 2023

Filters based on the interference of light in thin films are, no doubt, the most versatile of all spectral filters. Not only do they permit a very close control of the spectral characteristics of incident radiation, but they do so over a range of wavelengths extending from the x-ray to the sub-millimeter region. However, their performance is to a large extent governed by the optical constants of the materials available for their construction. There are spectral regions in which there is a lack of suitable materials and there the performance of filters based on thin film coatings is very rudimentary. Optical thin film filters also have an undesirable dependence on the angle of incidence of the radiation and are not suitable for the control of radiation over extended spectral regions. Furthermore, depending on the process used for their manufacture-, the performance of optical multilayer filters may change in time.
Immersed beamsplitters - an old problem
Authors: Macleod H Angus , Milanovic Zoran
Published: February 2023

45° angle of incidence in crown glass (n=1.52) is particularly difficult for p-polarization and normal dielectric materials. At that angle the typical normal incidence yH/yL ratio for zirconia/silica of 1.414 gives ηH/ηL of 1.794 and 1.114 for s- and p-polarization respectively. This great difference, and almost unity value for p-polarization, leads to very complex designs for even small spectral ranges. Metal layers are not affected to the same extent because the wave in them is virtually evanescent. We use modified admittances (rationalized by multiplying or dividing by cosθ0, where θ0 is the angle of incidence in the incident medium) and in this scheme the variation in metallic is almost entirely through the cosθ0 term. This still shows quite a change for s- to p-polarization but there is considerable contrast between the metal and any dielectric for both planes of polarization, making it possible to achieve something in design.
Effect of electric field on the growth of Al-film
Authors: Lee Cheng-chung , Lee Chii-hua , Chao Shiuh
Published: February 2023

Bias voltage applied to the substrate had been proved to be influential in the growth of gold and silver films1-2 and dielectric film.3

In this article we applied an electric field longitudinal to substrate by setting a high voltage of up to 2.4 KV during the growth of Al-films. (see fig. 1) Al-film was evaporated in high vacuum (10 μ torr) onto 1" diameter BK-7 substrate at room temperature.
Evaluation of Performance Limiting Factors in the Manufacture of Multilayer Optical Coatings
Authors: Gibson D R , Jones D P , Overend R B
Published: February 2023

This paper analyses achieved performance of three commonly used coating types, narrow band, notch and edge filter which are convenient design vehicles to identify and determine limiting effects of critical manufacturing factors relevant to production of general optical multilayer dielectric coatings. Fabrication of such a range of coating types, within a production environment, requires a high yield process with reproducibility of optimum coating performance over available deposition plant coating area and successive coating runs. Previous papers [1, 2] concentrate on specific aspects of optical coating manufacture, whilst few have addressed the general consequences of all effects on manufacturability.
Temperature dependence of the linear optical properties of organic thin films of dye-doped PMMA via surface plasmon spectroscopy
Authors: Sprague Robert W. , Lee John N.
Published: February 2023

Interest in organic materials for electro-optic device fabrication is due to the large molecular nonlinearities[1], the relative ease of fabrication[2], the ability to tailor the molecular structure through organic synthesis[3] and the potential for very high-speed low power devices[4]. The observation of an electric-field-induced quasi-permanent ordering[5], which eliminates the inversion symmetry and allows second order processes, has led to much work on the parameters which determine the degree[6] and the stability of alignment. This alignment induces a birefringence in the film[7] which is observed as the index perpendicular to the surface of the film via the surface plasmon[8].
Optical Characterization of TiO2 and SiO2 in Single Films and Double Layer Stacks
Authors: Edgerton Robert F.
Published: February 2023

We have been sputtering TiO2 and SiO2 for use in wide-band anti-reflection coatings on glass. We have made a study of the the optical properties of single material depositions of each of the constituent films on Corning 7059 and Silicon Wafer substrates. We have also taken some of the TiO2 depositions and deposited a SiO2 film on top of them during the same run in which the individual SiO2 sample was deposited. We are interested in knowing if the optical properties of the TiO2 or the SiO2 are affected by the deposition of SiO2 on top of the TiO2. Optical studies have been made of the six types of samples: SiO2, TiO2, and SiO2/TiO2 on the 7059 glass and Silicon wafers. Data has been taken with a Variable Angle Spectroscopic Ellipsometer (VASE ref. 1) from 300nm to 1000nm in wavelength and at a variety of angles of incidence from 50 to 80 degrees. In addition transmission and reflection data near normal incidence has been taken using a VW reflection accessory on a CARY 17DI dual-beam spectrophotometer from 350 nm to 750 nm. First the TiO2 ellipsometric data was analysed. The TiO2 was sufficiently transparent in the visible and near infrared that it was possible to set the extinction coefficient to zero and solve for the index of refraction and physical thickness of the sample. Having established a value for the physical thickness, the ellipsometric data, Psi and Delta, was used to find the value of n and k at each wavelength by a recursive process. After making many studies of several different samples of TiO2, it was found that the simplest way to characterize a particular sample of TiO2 was as a mixture of two extreme material types labeled TiO2 (Low Index) and TiO2 (High Index). We have used the effective medium approximation (EMA) to combine them and use the volume fraction of the TiO2 (Low Index) that is mixed into the TiO2 (High Index) as the adjustable parameter, vf10.
Characterization of Dynamic Indices by Stimulated Spectroscopic Ellipsometry
Authors: Gang Jin , Roger J.P. , Boccara A.C. , Stehle J.L.
Published: February 2023

Dynamic indices of multilayer structures can be extracted from stimulated spectroscopic ellipsometry. Using pulsed laser excitation, various heat diffusion processes through the structure can be separated.
Spin coating of TiO2 and SiO2 layers on curved CRT screens to form antireflex coatings.
Authors: Wimmers O.J.
Published: February 2023

Reflections from a CRT screen are very annoying for the viewer. They hamper the recognition of the image displayed on the screen and can even make it disappear completely. A reduction in reflection is possible by applying an antireflex coating on the outer surface of the screen. This has already been demonstrated on CRT's using evaporation as the deposition technique for the antireflex layers [1,2]. Another, and possibly cheaper, way to deposit antireflex layers is by spin coating them from sol-gel solutions [3 – 7]. In these studies the spin coating has been performed on relatively small substrates which were completely flat, without paying much attention to the thickness homogeneity of the layers on the substrates. For application of spin coating on CRT's, however, the substrate is the relatively large (14" diameter and up) curved outer surface of the screen, while the thickness uniformity of the coating over the entire screen has to be high. In order to see whether spin coating can be used to produce antireflex coatings on CRT's with a high thickness uniformity, both single TiO2 and SiO2 layers were spin coated on 14" CRT screens. In this paper, the thickness uniformity of these spin coated layers will be discussed. It will be shown that layers having less than 2% thickness variation over the entire screen can be made in this way.
A Hybrid Method for the Manufacture of Bandpass Filters for the Far-Infrared and Submillimeter Regions
Authors: Shao Jianxin , Dobrowolski J. A.
Published: February 2023

In a previous paper1 a method for the hybrid manufacture of reflectors for the far infrared spectral region has been described in which thin films of a high refractive index are deposited onto thick polyethylene films of selected thickness. A number of such films can then be combined by heat bonding. Through optical interference in these hybrid structures, high reflectances can be achieved. This has been verified experimentally.
Reststrahlen Material Bilayers an Option for Tailoring in the Infrared
Authors: Ribbing Carl G.
Published: February 2023

It has been reported that the reststrahlen band of beryllium oxide can be exploited for the purpose of frost prevention in situations when non-selective low emittance metallic coatings cannot be used1. The lattice band of high reflectance for beryllium oxide is strong in the region 9-15 μm which supresses the thermal emission in the primary atmospheric window 8-13μm. Consequently the radiative exchange of a BeO surface is limited to the surrounding atmosphere even if the latter is dry and clear. It was shown experimentally that less frost was formed upon BeO surfaces than on other alternative ceramic materials used as high power insulators. It was equally effective for frost prevention as conducting tin oxide on glass1.
Optical Thin Film Phase Quadrature Interferometry
Authors: McCall Susan H. C. P. , Dobrowolski J.A. , Shepherd G. G. , Sullivan B.T. , Wimperis J.
Published: February 2023

This research was motivated by the desire to improve the capability of Michelson Doppler interferometers in order to cope with situations of rapid temporal variablity encountered in upper atmospheric physics.1 A Michelson phase quadrature interferometer has been constructed using Phase Quadrature Mirrors (PQMs), based on optical multilayer coatings, in order to eliminate scanning mechanisms and achieve a fast time resolution over a very broad wavelength region. Other advantages include greater simplicity, improved ruggedness and lower cost.
Making aspherical mirror by thin film coating
Authors: Lee Cheng-chung , Wan Der-Shen , Jaing Cheng-chung , Chu Cheng-Wei
Published: February 2023

Spherical mirror can cause severe problem because of aberration. However the surface profile of the mirror can be modified to a desired aspherics by vacuum deposition if a proper mask is set between evaporation source and mirror.1–3 In this article we propose a mask for making a paraboloid. The monitoring system for deposition will also be described. The result aspherics is tested in a similar way for testing conventional aspherics.
Empirical Investigations of the Fourier Synthesis of Thin Film Designs
Authors: Willey Ronald R.
Published: February 2023

Dobrowolski, et al.(1) and Bovard (2) have reported extensively on the use of Fourier transform techniques to systhesize thin film designs. Both authors mention the approximations of the Q-functions which have been used to date and the limitations imposed by those approximations. Q-functions are the relationship of the amplitude in index of refraction versus optical thickness domain to the reflectance versus frequency domain. Bovard also discusses the frequency scale distortions around high reflection bands and how this might be approximately corrected. The Fourier technique shows great promise to provide a guide to the solutions for challenging thin film designs, and the referenced authors show how to obtain useful results in spite of the limitations and approximations. However, the two problems of the Q-function and the apparent frequency scale distortions have interested this author for some time as a result of an earlier collaboration with Verly and Dobrowolski (3) and our own subsequent investigations.
Scale-up Considerations for Codeposited Gradient Index Optical Thin Film Filters
Authors: Heuer J. P. , Eblen J. P. , Hall R. L. , Gunning W. J.
Published: February 2023

Refractive index tailoring by codeposition requires addressing issues that are not present, or at least subtle, in the case of sequential layer depositions. The two issues addressed in this work are the elimination of rate sensor crosstalk and reduction of the effects of refractive index modulation due to planetary rotation.
Rugate filter theory: an overview
Authors: Bovard Bertrand G.
Published: February 2023

The need for optical coatings fulfilling stringent optical and physical requirements has renewed a formerly existing interest in variable refractive index thin films also called “rugate filters”. Rugate filters are fascinating and challenging both theoretically and experimentally. This presentation will focus on their theory.
Thin Film Optical Coating Filter Stability under Different Environmental Conditions
Authors: Herrmann W. C. , Morton D. E.
Published: February 2023

Multilayer coatings have a propensity for the absorption of moisture depending on the porosity and/or density of the materials making up the thin film structure1. To some extent the degree of absorption can determine the durability of the coating and definitely affects the optical performance as the absorbed water molecules fill voids in the materials causing an increase in film indices. This effect can show up as a molted or blotchy appearing coating if the absorption is non-uniform, or irregular, over the surface of the coating or it can be a uniform shifting of the edge for multilayer edge filters2. For applications requiring tight transitions between transmission and reflection (beamsplitters) or high OD rejection of narrow visible bands with high photopic throughput (laser eye protection filters) this phenomenon translates to reduced manufacturing tolerance. Experiments were conducted in order to understand the degree of this effect and to determine how to specify moisture stability testing to assure meeting performance levels upon exposure to all anticipated environmental conditions.
Mystery of or Misery with TiO2 Coatings?
Authors: Balasubramanian K. , Richmond J. , Han X-F. , Guenther K. H.
Published: February 2023

Titanium dioxide (TiO2) thin films produced by conventional physical vapor deposition (PVD) techniques such as reactive electron beam evaporation typically have reduced packing density and refractive index. The porous and columnar microstructure of these films cause deterioration of their performance in varied environmental conditions primarily due to adsorption of water vapor. It has also been found that process variations adversely affect the reproducibility of TiO2 coatings much more severely than that of other films such as SiO2 and ZrO2. An inter-laboratory study conducted in 1986 and 1987 established that different processes and starting materials result in widely differing properties of TiO2 films.1 Such variations and rather non-controllable properties of TiO2 films present a tremendous challenge in manufacturing environment. As TiO2 is a highly useful material for multilayer optical coatings because of its high refractive index, a reproducible deposition process would be highly desirable.
Optical Properties of Tantalum Pentoxide Coatings Deposited Using Ion Beam Processes
Authors: Edlou Samad M. , Smajkiewicz Ali , Al-Jumaily Ghanim A.
Published: February 2023

Tantalum pentoxide (Ta2O5) coatings are widely used for optical applications. The material has a high index of refraction in the visible region (~2.2) with a wide transmission range which extends from 300 nm to about 10 µm. Coatings of Ta2O5 are used as a high index for interference coatings and as a protective coating, especially for high temperature applications. Deposition processes for Ta2O5coatings have been reviewed by McNally.1
Broadband Techniques for Monitoring Visible through Far-IR Rugate Filter Depositions
Authors: Lazo-Wasem Jeanne E. , Rahmlow Thomas D.
Published: February 2023

A rugate deposition monitoring approach is presented. Visible and FTIR insitu monitoring provides insight into the behavior of rugates during deposition and error analysis.
New Materials for the Production of Optical Coatings
Authors: Friz Martin , Koenig Friedrich , Feiman Stephen D. , McNally Stephen M.
Published: February 2023

We introduce two new materials for the production of optical thin films. PatinalR Substance H4 evaporant is a new mixture for high index layers of 2.1 at 500 nm. PatinalR Substance Ml evaporant is a new mixture for medium index layers of about 1.7 at 500 nm.
Estimating the Number of Layers Required and Other Properties of Blocker and Dichroic Optical Coatings
Authors: Willey Ron
Published: February 2023

We previously1 examined the estimations of what could be expected in the design of antireflection coatings. It is generally known that bandpass, LWP, and SWP filters can be made by properly positioning a QWOT stack or stacks to block or reflect the unwanted wavelengths. Thelen2 also discusses "Minus Filters" wherein the block band is in the middle of two passbands, one on each side. It is helpful when working with any of these designs to be able to estimate how many layers will be required to attain the desired reflection/blocking and how wide the blocked band will be. The optical density (OD = 1/ log Transmittance) increases almost linearly with the number of layers in a QWOT stack. The width of the blocking band increases with the ratio of the indices of the high and low index materials in the stack. The relative width of the blocking band is less with higher orders of the reflection band QWOT wavelength. We can use all of these facts to estimate how many pairs of a given material combination will be required to achieve a given result.
Polarization, Part-Polarization and Non-Polarization Beam Splitters on Substrate of BK7
Authors: Peifu Gu , Xu Liu , Jinfa Tang , Zhidong Zheng
Published: February 2023

Polarization, part-polarization and non-polarization beam splitters are widely used for various purpose.
The Application of Needle Optimization to the Synthesis of Optical Interference Coatings
Authors: Tikhonravov Alexander V. , Trubetskov Michael K. , DeBell Gary
Published: February 2023

The problem of optical coating design was first formulated as an optimization problem by Philip Baumeister in 1958 [1]. This approach is now the most widely used design technique for optical thin films. When formulated as an optimization problem it is possible to apply all the powerful tools of modern computational mathematics to the design of optical coatings. However, in many cases numerical solution of the resulting optimization problems are extremely difficult due to the large number of local minima in the merit function. Virtually all optimization methods are subject to convergence at local minima and for this reason a search for the global minimum or even "a locally optimal minimum" is a formidable problem.
Optical Coatings Without Phase Dispersion For Fabry-Perot Interferometer
Authors: Lemarquis F. , Pelletier E.
Published: February 2023

Phase dispersion is a critical point in Fabry-Perot interferometer [1], Here, we propose a solution to avoid it.
Visible Broad-Band, Wide-Angle Thin Film Multilayer Polarizer
Authors: Li Li , Dobrowolski J.A.
Published: February 2023

The performance of polarizers based on the interference in optical thin films has been recently reviewed.1
AR Coatings Designed For Two Different Substrates
Authors: Dobrowolski J.A. , Panchhi Parmjeet , High Martin
Published: February 2023

In a commercial thin film coating shop hundreds of different substrates need to be antireflection-coated every month. These substrates are frequently made of different materials. The construction parameters of an ideal antireflection coating depend on the spectral region over which the reflectance is to be reduced and are usually different for each substrate material. This means that substrates of different materials need to be coated in separate runs.
Relaxation time of light induced refractive index modifications in dielectric thin films
Authors: Monneret S. , Flory F. , Rigneault H.
Published: February 2023

The totally reflecting prism coupler has been used for many years to determine refractive indices, thicknesses, or anisotropy of thin films [1]. It also enables us to study reversible disturbances of the optical properties of films materials with the temperature [2] or with the light beam power [3].