Optical monitoring methods and their integration into automated vacuum coating systems are reviewed. Special attention is paid to monochromatic monitoring, the achievable monitoring accuracies, error compensation and error accumulation effects and the on line correction of trigger points. Finally a microprocessor control system with integrated monochromatic thickness monitoring is described.

The increasing demand for complex multilayer optical coatings requires equipment with a completely automated process control system. The new optical thickness monitor GSM 420, which is part of the deposition control system BPU 420 allows the remotely controlled wave-length selection either with a grating monochromator combined with the appropriate order sorting filters or with a set of six narrow bandpass filters. The endpoint detection is based on the digital processing of the signal corresponding to the light intensity after transmission through or reflexion from a testglass located side by side with a quartz crystal microbalance at the center of the coating plant. Turning value monitoring or termination of the process at an arbitrary predetermined point are both possible. Single and multiple layers of silicon dioxide and titanium dioxide and combinations thereof were deposited. Excellent linear correlation between the optical thickness on the test glass and the geometrical layer thickness as measured by the quartz crystal microbalance was observed. The reproducibility for single layers of quarterwave thickness was found to be between ± 0.7 to ± 1.7 % of the center wavelength of the spectral extremum measured on the test glass, depending on wavelength (350 - 3200 nm) and coating material (SiO₂ or TiO₂ on glass).

A microcomputer based evaporation monitoring system is presented which operates on a standard production plant equipped with standard thin film measuring devices: photometer and quartz crystal monitor. The computer acts as an evaporation data acquisition and storage system. The transmission T of a sample substrate as well as the film thickness d taken from the quartz monitor are recorded digitally vs. time. The T-d relation is on line least-squares fitted to the theoretical T-d function of an arbitrary nonabsorbing homogeneous layer deposited on an arbitrary stack. Using the fit function an optical thickness can be expressed in terms of the linear parameter d for instance as trigger point for termination of the deposition process. The procedure is especially suitable in turning points. In non-absorbing systems the fit function directly yields the refractive index of the layer.

A broadband antireflection coating on BK 7 was used to investigate the influence of dif-ferent optical monitoring strategies on the reproducibility of the completed layer system. The coating design consisted of 6 alternating layers of MgF₂ and TiO₂ of which 4 layers had optical thicknesses less than a quarterwave. Two different monitoring strategies were tes-ted: single test slide monitoring (all layers on one test slide) and monitoring of each layer on a separate test slide. Each strategy was tested by performing 10 production runs in a completely automated coating system equipped with a monochromatic photometer. The single test slide method proved to be more reproducible for the production of this specific layer system.

Filters intended for demultiplexing radiations whose wavelengths differ from some 20 or 30 nm must exhibit high performances. Fabry Perot filters with high finesse and contrast are generally used: single Fabry Perot filters fulfilling these conditions are made with a large number of quarterwave layers. The contrast can be improved by using a system constituted of several single Fabry Perot filters in series (D H W, T H W). To carry out the production of such filters with very strict manufacturing tolerances, a direct optical monitoring method has to be used. In this case, following up the evolution of the optical properties of the stack during its growth allows an automatic error compensation to be obtained. We have developed an apparatus allowing a continuous observation of the spectral profile of the filter during its formation, in a range of some ten nanometers centered on the peak transmission of the filter. For the centering wavelength of the filter, calculation and evolution of the two par-tial derivatives ∂T/∂e (with respect to the time) and II1/X (with respect to the wavelength) can then be made. With some precise examples, a discussion about the sensitivity of the different methods together with the choice of the best fitted one for the stack monitoring is presented.

The degree of cleanliness of optical surfaces to be coated with an interference film or a metallic layer by means of high vacuum deposition is of crucial importance to the coating result. Among the various possible cleaning technologies, ultrasonic precision cleaning has proved to be economical and technically efficient. This paper explains the type of cleaning requirements that can be satisfied with a modern ultrasonic cleaning plant. It is, for example possible to clean sensitive glasses (up to acid resistance class 52) sufficiently well so that they are suitable for coating. The influence of the polishing condition on the surfaces to be cleaned is discussed in detail. The limits of ultrasonic cleaning technology are also pointed out.

In the field of mechanical fabrication, computer numerical control (CNC) of machine tools has become very mature in the past decade. The same potential exists for optical coating production, but has lagged in time due to the increased number and complexity of the parameters which have to be controlled. In the past few years, it has become possible to purchase CNC optical coating systems with reasonable capability and reliability. This paper reviews the capabilities and status of various CNC coating systems which have been surveyed.

Programs for the design of optical multilayer systems at the NRCC are based on analysis, refinement, comprehensive search, gradual evolution and on the minus filter, flip-flop and inverse Fourier transform methods. For the purpose of this paper they have been used to design layer systems with one particular spectral transmittance curve. However, they can be applied to a wide variety of problems. Their advantages and limitations are compared and contrasted.

A method of designing multi-cavity infrared narrowband filters for bandwidth between 10% and 20% is presented: the method is based on a Tschebyshev prototype. The theoretical indices from these are simulated by Herpin equivalent layers, the outer layers may be also simulated by Herrmann's asymmetrical tri-layer. The new algorithm of filter design can easily be implemented in any microcomputer.

The design of an antireflection coating on glass for the visible spectrum is made in order to examine the performance of AR coatings composed of only oxide layers compared to coatings made using oxides and fluorides. The materials employed for such design are silicon dioxide and titanium dioxide both of very common use in optical coating manufacture. The design method is based on a random search approach that is especially useful when the examined problem could have multiple solutions. The results obtained in terms of reduction of reflectance losses and of sensitivity to thickness errors demonstrate a good production feasibility.

Ttedesign philosophy of MC-AR-Coatings can be divided into two categories: a) Restriction to two film materials, namely one high-index and one low-index material and b) Use of medium-index layers in addition to high- and low-index layers. Both philosophies have advan-tages and drawbacks. In case a) the total number of layers necessary to obtain a required reflectance curve has to be higher. Thus in case of production errors it can be a problem to find out which layer was responsible for a deviation of the measured reflectance from the nominal one. In case b) using more than two materials reduces the total number of layers and consequently, pinpointing the cause of even small production errors is made simpler. Unfortunately there are not many materials commercially available which can be used to make hard, durable and robust films in the medium-index range namely between n=1.65 and n=2.00. In this paper the results of homogeneous mixtures of Alumina (Al₂0₃) and Tantala (Ta₂0₅) used for EB-gun evaporated medium-index films in AR-coatings is presented. It is shown that by proper adjustment of the weight percentages of the oxide mixture one can get homogeneous films in this index range. A number of design examples show the favourable application of such layers in AR-coatings. Among the most important ones is the well known QHQ-design for BBAR-coatings as well as AR-designs of the multiple half wave type with extended bandwidth. Further applications of the mixed-oxide layers are AR-coatings for cemented optical elements and beam splitters.

This paper presents description of a versatile software package for computer-aided design of thin film optical coatings, which has been developed by employing latest version of Turbo Pascal Language and can be run on any IBM or compatible personal computers. Both numerical and/or graphical output for transmittance and reflectance of a multilayer dielectric structure at various wavelengths are easily obtained. Other features in the package include interactive monitoring of thin film coatings during deposition process, saving of input parameters and results in the form of files, a look-up table for commonly used materials and facilities to provide parameters to an optical thickness monitor.

A complete treatment of the characteristic admittance-matrix representation of multilayer thin-film systems with absorbing media is presented. The algorithm from the systems' analysis is implemented on an IBM microcomputer and some examples of filter design calculations are presented. Relevant source code in IBM ADVANCED BASIC interpreter are also included.

New software increases the performance and capability of desktop computers utilized in the design and manufacture of optical thin film interference coatings. Algorithms related to technical capability and user interface are discussed.

A small desk top computer, when properly programmed, can be used in the design of optical coatings, analysis of new designs, for instructions to coating machine operators, cost estimations, and to help in the computation of machine tooling.

As the deposition of thin films does little, if anything, to improve the light scattering characteristics of a component but adds greatly to its cost, the current growing interest in improving the quality of substrates is understandable. Process control does, of course, require the use of adequate means for measuring the parameters which need to be controlled. This paper will compare and contrast the subjective methods employed in a number of standards with a variety of objective techniques developed in recent years, taking into account the requirements of both on and off-line inspection. Surface parameters to be discussed will include form, roughness, waviness, flaws and contamination, as all these have an adverse effect on the performance of the component to an extent depending on the application. The review will attempt to present a picture of current practice and suggest possible ways in which the process of surface inspection could be improved in future by the use of objective methods of measurement and standards, involving some photometry, rather than relying solely on visual assessment.

A vacuum reflectometer for the UV and VUV spectral range was developed for qualification of optical components below 400 nm. Typical performances, in the 120-320 nm spectral range, of filters and mirrors offered by MATRA will be presented. Fitted with various gratings and sources this device allows reflecting, transmitting power as well as scattered or diffracted flux measurements (gratings efficiency measurements) until 25 nm.

The inverse synthesis method is investigated for its ability to deduce the construction parameters of a complete layer system from its reflectance or transmittance curve at nor-mal incidence. To avoid multiple solutions the theoretical design of the layer system is used as a starting design and by subsequent optimization the actual construction parameters can be found. The impetus of this work was to develop a tool for the thin film engineer to speed up thin film development. A 6-layer broadband antireflection coating is used as an example for testing the inverse synthesis method. The necessary measurement accuracy for the spectral reflectance is discussed. A series of 10 successive production runs is analyzed. The variations of layer thicknesses from run to run are given.

Reflectance, angle-resolved scattering and total integrated scattering (TIS) measurements of surface roughness are reported for a number of Al/MgF₂ coated mirrors. Reflectances are given for the 160 - 250 nm wavelength region and scattering is measured at 160 nm and 633 nm. Both replicated aspherical mirrors and flat, unreplicated samples were investiga-ted. Replicated mirrors with an interdiffusion barrier layer retain their high reflectance properties in the far UV although heated to 100 0C for 2 hours. Absorption dominate intensity losses for most of the mirrors, but scattering observed for two of the samples severely degrade the far UV specular reflectance. Angle-resolved scattering measurements at different wavelengths are demonstrated to be a useful technique for tracing scattering mechanisms. Light scattering in the visible is shown not to be representative of the scattering observed in the far UV, as strong particulate scattering at 633 nm vanishes at 160 nm. The possibility of using angle-resolved scattering for roughness determination of curved surfaces is briefly discussed.

Some outstandi,,g features of a new device for hardness measurements in a SEM are presented and its capability in optical applications is demonstrated. It will be shown that both the quantitative hardness deterhuination fmail. imprint size as well as a visual observation of the imprint topology are essential for quality assessment.

Due to the definition of classical indentation hardness, the plastic behaviour of a material is investigated. But in the load-dependent range the influence of the elastic deformation also becomes noticeable. There is a remarkable difference between diagonal length and resulting hardness, in case of a pure dielectric and a dielectric with thin ductile metallic overcoat required for examination in a scanning electron microscope (SEM). According to the almost plastic behaviour of the overcoat, the diagonal length of the imprint produced by a diamond indenter under load, i.e. before elastic backformation, is "fixed". So it is necessary, in contradiction to investigations made with precoated dielectrics, to produce indents on the pure surface, for instance with Reichert-Jung Micro-Duromat 4000, and to measure them with a light microscope or, in the case of too small indents, with a SEM after coating with a thin conducting film.

The preparation of non-hydrogenated and hydrogenated amorphous tetracoordinated semiconductor films, their structure, the influence of disorder and defects on the density of states and the role of hydrogen are briefly reviewed. Different methods of determination of the optical constants of these films are described, with special emphasis on the low-absorption range. The optical properties are analysed in detail, and characteristic parameters giving information on the amount of disorder and defects are discussed.

The refractive index of some dielectric thin films has been determined by three different techniques. Spectrophotometry, ellipsometry and a technique based on the Abeles method are chosen for the analysis of the prepared samples in the visible spectrum. The first technique is the most widely used for obtaining a quick evaluation of the refractive index but, in order to get accurate results, a complex data processing is necessary. The second one is the most accurate but the experimental apparatus is rather complex and a skilled operator is generally required. The third technique is simpler than ellipsometry and a comparable accuracy on the refractive index determination can be obtained but only for transparent films. The relative advantages and limits of these techniques make each of them more or less convenient depending on the sample properties. Results are compared in areas where all three methods are successfully used.

The optical constants n and k for a weakly absorbing thin film material can be determined from the transmission scan of a single thick layer of the material coated on a substrate. The envelope method makes use of the wavelengths and transmittance values of the maxima and minima of a spectral scan to determine the optical constants. The values and positions of these extrema are affected by the dispersion of the optical constants. The dispersion of the index affects the position of the odd quarterwave extrema, but not the halfwave extrema. The effect is small (typically 0.5%) for high index oxide materials. The dispersion in the extinction coefficient causes larger errors, especially near the absorption edge where the extrema can be shifted by several percent. The effects of the dispersion are calculated and the results are used to obtain more accurate values of the optical constants and thickness of the film. The various errors and the resulting corrections to the optical constants are compared for a typical high index oxide film.

The optical properties of noble metals and the 4th group transition metal nitrides are reviewed. Special emphasis is placed upon the similarities and differences in the free electron like behaviour in the two groups of materials. The free electrons in the noble metals have s-character while the conduction electrons in the nitrides are d-electrons, whose interband transitions are suppressed. Recent improvements in the optical performance of transparant silver and titanium nitride films are described and their optical constants are reported.

An accurate technique for determining the optical constants of thin absorbing films as components in an amorphous semiconductor multilayer is presented. The case of films of Indium Tin Oxide (ITO) covered with a film of hydrogenated amorphous silicon has been investigated since it is of relevance in the solar cell field. Transmittance T, reflectance R and reverse reflectance R' were measured for the single films ( a-Si:H and ITO) on the substrate (quartz) and for the bilayer a-Si:H/ITO; from these measurements the indices of refraction (n) and extinction coefficients (k) were obtained. Depending on deposition temperature, the optical constants of a single a-Si:H film are remarkably different from those of the same film when it is part of a bilayer structure, especially in the short wavelength region. Also the value of the energy gap in the bilayer case is smaller than in the monolayer case.

The Mean Field Theories developped for the dielectric function of inhomogeneous media (metallic clusters in dielectrics), do not give a proper account of the optical properties for metal volume fractions around the percolation critical fraction. We present a new phenomenological derivation of the Bruggeman formulation valid in the near and middle infrared near the percolation. We first separate the different contributions to the dielectric function in the Bruggeman expression and point out their physical meaning, below and beyond percolation. We show that the conduction and the static dielectric function are predicted to follow scaling laws with an exponent equal to 1. This value does not agree with the critical exponents (s and t) deduced from Monte Carlo simulations and renormalization calculations. A new formulation is proposed by replacing the exponents 1 by their proper values. This formulation is successfully applied to our results on the optical properties of Au-Mg0 and Pt-Al₂0₃ cermet thin films.

The optical properties of polycrystalline silicides layers have been investigated by reflectivity measurements from the near I.R. to the near U.V. The influence of the metal nature (Ni, Pd, Pt) and of the silicide stoichiometry has been studied. The electronic den-sities of states have also been measured by X-ray photoemission spectroscopy. We show that two different classes of silicides may be distinguished independently of the metal. Metal rich silicides have optical spectra qualitatively similar to those of the metals. On the contrary, the reflectivity of Si rich silicides is very different. There appears a sharp near I.R. cut-off and well defined structures in the visible range. Based on published band structure calculations and our XPS measurements, we associate these phenomena to a partial decoupling between the free electrons contribution and the interband transitions from d derived states to the Fermi level.

Valuable information is lost when light is viewed merely as a photon flux, overlooking its essential polarization character. Consequently, conventional near-normal-incidence (R, T) optical monitors are basically inefficient. Instead, we recommend that the next generation of optical monitors use ellipsometry and photometry on the reflected and transmitted beams, simultaneously, to extract six parameters (R,ψΔr, T, ψt, Δt) at the observation angle of incidence and at each wavelength. This additional data can be used for more complete characterization of the deposited thin films, including anisotropy or index gradients. A simple test for anisotropy or inhomogeneity in a growing transparent thin film based on the ratio of complex transmission coefficients ρt = tan ψt exp(jΔt) is presented.

Laser damage to optical coatings is often the factor which limits the fluence levels that can be achieved with high-energy laser systems. Laser damage to coatings may be caused by a number of mechanisms: the intrinsic optical properties of the coating materi-als, such as absorption; the mechanical, thermal or chemical properties of the films, such as stress, microstructure, thermal conductivity and chemical composition; and extrinsic factors, such as contamination from the polishing, cleaning and coating processes. The solution to the problem of laser damage to coatings is complicated by several factors. The coating process involves a large number of parameters, many of which are not accurately controlled or understood. Methods of characterizing the optical, mechanical, thermal and chemical properties of materials are often difficult to apply to thin films, especially with a spatial resolution of a few microns or less. In addition, several different processes may contribute to laser damage, making it difficult to isolate a single cause. Although much progress has been made in recent years, there is still a need for a long-term research effort involving the close cooperation between an experienced coating facility and a dedicated laser damage testing laboratory.

Different strategies are illustrated that can be used with the inverse synthesis method for the determination of the optical constants of coating materials.

Summary of the introductory presentation for a panel discussion on "Characterization of optical thin film" The determination of the refractive index and the extinction coefficient of optical thin films can be nowaday higly accurate wheter carried out by skilled operators. Reliable results can be obtained even for inhomogeneous layers or for films with non-uniform thickness and measurements during the film deposition can also be performed. The accuracy of results, however, depends on the instrument performances in addition to the operator skill. In fact high accuracies require complex and expensive measurements apparatus, often "ad hoc" made, and data processing must be performed by people able to understand the physical meaning of the obtained results. Often a very high accuracy on the determination of optical constants is not required provided easy and fast measurements methods can be employed. In these cases a careful choice of the method and the relative measurements apparatus is necessary and some practical clever-nesses must be used for avoiding those mistakes possible even though advanced instrumentation is employed. In the present discussion the techniques most widely used for n and k determination will be surveyed and some practical suggestions will be made aimed at ensuring that measurements and data processing are performed correctly.

In the various phases of the development, production, and use of optical thin film coatings, it is vital to choose proper materials not only with respect to their optical properties but just as essential with respect to their environmental durability. If envi-ronmental tests reveal failures in optical coatings, this may be due to interactions between the layers and/or between the substrate and the first layer. Such interactions can be established and analyzed by depth profiling using electron- and/or ion-beam methods. Empha-sis must be placed on the practicability of these analysis methods with dielectric coatings where difficulties may sometimes arise because of decomposition, diffusion or intermixing, and charging effects during analysis.

Light scattering measurements can be used both for quality control and as a tool for characterization of thin film properties. Thin films contribute scattering from surface irregularities at interfaces and from inhomogenities in the film structure. For multilayer stacks correlation effects may also be present. The most refined scattering theories invoking both surface roughness and inhomogeneous dielectric permittivity show good agreement for a limi-ted number of experimental cases. Grain sizes and shapes in the film, are not treated in this theory but these become increasingly important at the shorter wavelengths, i.e. in UV and EUV. In general, incident polarized light and angle-resolved detection of the scattered light is a good way to get a more fundamental understanding of the thin film scattering process. By extending the scatter measurements into the extreme ultraviolet, more information about the sub-micron irregularities can be gained.

Optical-coatings problems can be traced to the microstructure inherent in the optical-coating process of thermal evaporation in vacuo. Ion and photon bombardment techniques have been associated in various ways with thin-film deposition. Some processes that incorporate these techniques improve optical-coating performance. Processes relevant to optical-coating construction are surveyed and some recent results are discussed. Ion-assisted deposition and laser evaporation are identified as particularly promising optical coatings.

The optical constants of thin films of silver and titanium nitride have been obtained in the visible and near infrared spectral regions by the Nestell-Christy method. The silver films, 9-.27 nm thick, were prepared by d.c. magnetron sputtering at low pressures. It is found that the silver films, prepared at sputtering pressures below 2 mTorr, retain their bulk optical constants down to 13 nm film thickness. 5- 31 nm thick TiN films were depos-ited by reactive d.c. magnetron sputtering on 4000C heated glass substrates. The substrate heating increased the IR reflectance of the film with preserved transmittance. The free-electron character of the thin TiN films is maintained in the thickness range 13- 31 nm, as is plain from the behaviour of the optical constants. A common observation for the Ag- and TiN-films is that a low refractive index in the visible is a more sensitive criterion on film quality than the extinction coefficient. From the Drude analysis in the infrared spectral region the free-electron plasma energies and relaxation times have been derived and comparison with previous data have been made. The present results are of interest for heat-mirror development and the performance parameters for such applications are calculated and discussed.

Photo-CVD Silicon Nitride thin film have been deposited at low temperature for optoelectronic devices application. The main features of the thin layer deposition system are low substrate temperature (50+250°C) and absence of charged particles damage during deposition. The results obtained concern the relationship between refractive index, infrared spectra, chemical etching, step coverage, adhesion and deposition parameters.

Argon ion bombardment conditions to obtain Ta₂0₅ and Si0₂ layers with a minimal optical absorption and a packing density close to one are defined. Applied to multilayers, these techniques give filters with an excellent stability of their optical properties when exposed to a moist atmosphere.

Measurement of spatial distribution of scattered flux combined with a vector theory of surface scattering, leads to the characterization of micropolishes in modern optics. Our techniques for transparent and non-transparent substrates are described. When applied to multilayer optical coatings, the scattering studies give informations on material microstructure defects. Recent developments realized in Marseilles in this field are analized.

Total integrated scatter (TIS) measurements are discussed on the basis of the proposed ASTM standard for surface characterization. A TIS-apparatus built in accordance with this standard is presented and measurements are reported for samples ranging in roughness from 1 A to 150 A. Si-wafers are demonstrated to possess excellent surface quality and made measurements of roughness from an 1100 A Al-film possible.

Laser calorimetry is used to measure the optical absorption in both bulk materials and filmed substrates with total system absorptance of 1 x 10^-2 and below. This paper reviews the various sample configurations, data analysis schemes, and calorimeters that have been used to make these very low absorption measurements.

There is, presently, a great deal of experimentation going forward on the use of rugate coating techniques. In the simplest form, a rugate coating is composed of a single material wherein the disposition conditions are modified to change the index of refrac-tion. Ideally, one achieves a homogeneous material wherein there are no severe discontinuities similar to that found in a multilayer optical stack. Because the material appears to be homogeneous, it is argued, the coating is much more thermally coupled to the substrate, thereby obviating the mechanical bonds of a multilayer stack and the subsequent thermal resistances of the interfaces. Based on the theoretical model described by Palmer 1, the rugate coating temperature gradient may be evaluated as a function of the electric field standing wave and the absorption distribution. The transient conduction and subsequent temperature buildup for one dimensional and three dimensional models will be described. The mathematical techniques are reviewed for both continuous wave laser power and for repetitive pulsed laser power. Key words: High Energy Laser, Optics, Optical Thin Films, Heat Transfer.

There is, presently, a great deal of experimentation going forward on the use of rugate coating techniques. In the simplest form, a rugate coating is composed of a single material wherein the disposition conditions are modified to change the index of refrac-tion. Ideally, one achieves a homogeneous material wherein there are no severe discontinuities similar to that found in a multilayer optical stack. Because the material appears to be homogeneous, it is argued, the coating is much more thermally coupled to the substrate, thereby obviating the mechanical bonds of a multilayer stack and the subsequent thermal resistances of the interfaces. Based on the theoretical model described by Palmer 1, the rugate coating temperature gradient may be evaluated as a function of the electric field standing wave and the absorption distribution. The transient conduction and subsequent temperature buildup for one dimensional and three dimensional models will be described. The mathematical techniques are reviewed for both continuous wave laser power and for repetitive pulsed laser power. Key words: High Energy Laser, Optics, Optical Thin Films, Heat Transfer.

Using a surface roughness model consisting of narrow columns of differing heights, the spectral transmittance and front and backside reflectance have been derived for a single layer on a smooth substrate. The effects of various amounts of surface roughness have been compared to various amounts of layer absorption. Surface roughness causes a more rapid loss of modulation with wavelength in transmission than absorption. It begins to act like incoherent light, which shows no wavelength fringing.

The well-known evaporating process of hard-oxid coatings for laser mirrors has many uncontrolled parameters. This paper deals with the Ti0,-SiO2 hard-oxides systems. The optimization of technology is based on optical [transmission; reflection parameters etc), spectroscopical [soft x-ray emission spectroscopy /SXES/, x-ray fluorescence spectroscopy /XFS/], structural (x-ray diffraction /XRD/) and damage threshold /DT/ examinations. The Ti02 was found in the evaporated layers in two equilibrium phases - rutil and anatase - depending on the evapora-tion conditions. The rutil phase was better than the anatase considering the DT for mirrors at λ=]1064 µm. The explanation is based on the difference of the near-infrared absorbtion between rutil and anatase phase of Ti0₂.

Following Seddon we divide optical coating products into performance sensitive and price sensitive products.

Multilayer X-ray mirrors have been deposited by triode dc sputtering using a new method of thickness monitoring which is based on the dependence of the deposition rate on the target current. Thicknesses can be controlled with an accuracy of better than 0.1 ⟨. High efficiency W-C, and Ni-C multilayer mirrors have been synthesized and tested at 1.54 Å (Cu Kα) and 44.79 Å (CK,α). Absolute reflectivity measurements at λ = 44.79⟨ (CKD) have been carried out. In this case the incident beam is previously polarized by a premonochromator equipped with a pair of parallel plane multilayer mirrors fixed at an angle close to Brewster's one (0---,45°). Thus the measured reflectivities are not affected by a progressive variation of the P component.

High-efficiency, p-suppressing, infrared reflection polarizers that employ a high-index transparent thin film on a low-index transparent substrate are described. Examples are given of such polarizers using infrared-transparent semiconductor films of Ge and Si on Irtran and glass substrates at the 2.8 μm (HF) and 3.8 pm (DF) laser wavelengths. The unextinguished power reflectance for the s polarization is high, as Z95 %, and is comparable to that of thin-film reflection polarizers that use metallic substrates. The effect of small changes (or errors) of film thickness, angle of incidence and wavelength on the extinction ratio of the device is also considered. Because of the high efficiency of the single-reflection polarizer, two, three or four such elements can be cascaded to achieve (1) parallelism or collinearity of the input and output beams, and (2) very low extinction ratio for the compound polarizer, while maintaining appreciable throughput for the passed (s) polarization component.

We present an algorithm for the computer simulation of evaporation processes and a method to characterize the emission patterns of the evaporation sources. The parameters taken into account on the algorithm, describe the geometry of the evaporation chamber, detectors, substrate and substrate holder, as well as the kinematics of the planetary or calotte. The numerical algorithm produces the appropriate parameters for the optical and quartz detectors to be fed to the controler during authomatic production runs. The characterization of the emission patterns of the sources is achieved through the study of the monochromatic transmission bands on a series of multilayer Fabry-Perot filters. These patterns are modi-fied by an orthonormal polynomial series expansion. The polynomials are determined by extensive data reduction of the film taper-thickness as a function of position. The large circular flat glass substrates used, were kept static during the process of evaporation in order to obtain the specific thickness distribution for each type of source. Experimental results are compared to the computer simulations.

The values of shifting of the spectral curve for an optical titania/silicia multicavity filters in the 400 - 700 nm range after deposition are described.