The current two major non-numerical design methods, equivalent layers and polynomial synthesis, are reviewed and compared. The equivalent layer method works well when only a small number of fixed refractive indices is available. This is the case when the coating is manufactured by evaporation. Polynomial synthesis generates a priori better designs but does not allow predetermination of refractive indices. So, for evaporation, the designs have to be translated from many refractive indices to a few. This process generally downgrades the design. This translation is not necessary when sputtering or chemical vapor deposition is being used. Here, in-between refractive indices can easily be generated by mixing or flip-flopping. As a consequence, superior designs can be implemented.

The properties of multiple-layer dielectric systems of low absorption are considered. The possibility is demonstrated of application of conducting surface model for the cases when absorption is concentrated near the layer boundaries. The formulas for calculation of such systems are presented. Special attention is paid to the calculation of quarter-wavelength slightly absorbing mirrors, including the case of oblique light incidence.

As a consequence of advancements in inertial confinement fusion research, LLNL is developing plans for a new 1.5 to 2 mega-joule solid-state Nd:glass laser designed to achieve fusion ignition. The new design is possible in part due to advances in optical coatings suitable for high-power laser systems. High damage threshold mirrors and polarizers are comprised of electron-beam deposited dielectric multilayers. Subthreshold illumination, or laser conditioning, of the multilayer coatings results in an increase in the damage thresholds by factors of 2 to 3 at 1.06 micrometers , thus meeting the fluence requirements of the advanced architecture. For anti-reflective coatings, protective organic coatings for non-linear crystals and phase plates for beam smoothing, sol-gel films provide high damage thresholds coatings at low cost.

An outline is given of how advantages of conventional magnetic recording have been combined with those of compact disc technology to establish a method of high density magneto-optical recording, where information can be erased and freshly recorded at potentially very high superficial density and data rates. Application of the principles of thin film optics to the design of multilayer recording media with optimized magneto-optical `read' characteristics are emphasized, and possible future developments are discussed.

Recently the phenomenon of induced resonance absorption (INDAB) in thin films has extended the technological range of applications for optical layers noticeably. The INDAB characteristics, being significant for practical purposes, are at first an extremely high volume density of absorbed radiant energy in thin films: ideally, the total absorption in film thicknesses which are small compared to the penetration depth of radiant energy in the unlimited medium; secondly, a possible control of spatial absorption distribution within the INDAB layer. The INDAB effect is an example of how thin optical coatings exert their important function on today's complex high technology systems. It demonstrates convincingly that thin films affect a wide field of applications, especially by initiating, promoting, or optimizing a multitude of semi-optical processes. (A `semi-optical process' in this context, for instance, means an energy conversion from optical to non-optical and vice versa, especially photothermic, photochemical, and photoelectronic phenomena.) This paper illustrates the basic principle of INDAB, and in giving an example of application demonstrates the innovation ability and the increase in efficiency by use of INDAB.

Previously published works on the use of Fourier transforms to synthesize thin film designs have mentioned two problems. One has been a lack of a relational function of reflectance to the index profile, or `Q-function,' which gives satisfactory results for both high and low reflectance cases. The other is that the reflectance versus frequency profiles of well known results, from the matrix approach, showed a significant distortion for high reflectors. Our investigations have concluded that the transform of the simple reflectance amplitude versus optical thickness gives correct results in reflectance versus frequency for all cases when multiple reflections are properly taken into account. The limitation of using only non- dispersive and non-absorbing media still applies to this work. The challenging antireflection coating problem posed for this meeting (a 400 to 900 nm bandwidth and less than 1% reflectance from 0 to 30 degrees) is used as an example to see what insight may be gained by the use of Fourier and related viewpoints.

Thin film coatings having a radially variable reflectance with a circular symmetry are used for obtaining diffraction limited laser beams from unstable resonators. Different approaches are used for the design of such coatings with a consequent different final coating structure that contains one or more profiled thickness layers. Some design methods are discussed with reference to reflected intensity and phase profiles and the fabrication techniques for coatings at different wavelengths are illustrated.

Second order optimization methods such as the Newton-type methods are known to be extremely effective in solving various inverse and synthesis problems. Despite this they were not used for thin film optical coating design. The reason is a great difficulty in Hesse matrix calculation. We have found a mathematically strict approach increasing the performance of Hesse matrix calculation many times. It allows us to use various second order optimization methods in our new design program called OptiLayer. On the other hand, specific optimization methods based on the optimal control theory results were used to enhance the program efficiency. As a result a very powerful tool for optimal coatings design was received. The developed software allows the user to design complicated optical coatings consisting of many layers (up to several tens) and possessing non-standard spectral properties. The software easily allows the user to take into account various feasibility demands.

Gradient index coatings, or rugate filters, may be of interest to more easily achieve optical properties such as `notch' filters that are difficult to reach with classical multilayers. Rugate coatings have been fabricated using a new evaporation system. This system uses two coupled masking devices to control the rate of two sources kept at constant temperatures. Two couples of materials were studied and sine wave index profile rugate filters were fabricated.

System design is a method to realize system synthesis -- a special form of system identification -- that means, the determination of a system S corresponding to a given behavior. In synthesis this behavior is prescribed and S has to be constructed accordingly. The other form of identification is system recognition, where one has to find the structure of an existing system from a behavior given by measurements. In both cases the mathematical methods used won't differ essentially. For thin film systems the behavior is given by functions depending on the wavelength and/or the angle of incidence of a harmonic plane wave.

Optical interference coatings which have been successfully used in Chinese FY-1 Meteorological Satellite and airborne remote sensing instrument are described. These include system requirements for these coatings, design approach, fabrication technique, and the actual results achieved.

The thickness uniformity of vacuum deposited layers is a very important parameter for optical coatings. We have developed a computer program for the calculation of the uniformity as a function of the vapor distribution for planetary systems. This program shows the existence of a configuration such as the uniformity is practically independent of the vapor distribution. We give the example of an experimental system for processing four substrates of 300 mm diameter with a uniformity better than +/- 0.3% in a 1 m³ box coater.

Ternary II-VI semiconductors, like CdS_xSe_1-x or Zn_xCd_1-xS, were prepared by thermal evaporation of binary semiconductors from a double source. The influence of substrate temperature during thin film deposition and of thermal annealing in argon atmosphere on absorption edge steepness is studied. A high absorption edge steepness is advantageous to achieve large resonant optical nonlinearities, like absorption bistability and electronic nonlinearities. The position of the absorption edge can be tuned by choosing a proper film composition. Thermally induced optical bistability is demonstrated. Electronic nonlinearities are investigated in ns- and ps-pump-probe experiments. Fast bleaching with < 60 ps relaxation time is observed at the absorption edge. The maximum bleaching coefficient for CdS_0.69Se_0.31 films is 1.4 cm/kW at (lambda) equals 587 nm for pumping with (lambda) equals 377 nm. Annealing the films showed no effect on the relaxation time, but the bleaching coefficient was increased by a factor of five.

Ellipsometric spectra of thick polymer films for non-linear optics were recorded at several angles of incidence. A non-linear regression analysis is used to compare an isotropic model to a uniaxial one. Analysis in the transparent region unambiguously points out the more suitable model, and the corresponding thickness. These results are subsequently used on all the spectrum, including the absorption domains, so as to give the complex ordinary and extraordinary indices. Relevant structural information on the polymer conformation is then inferred.

The optical properties of differently deposited amorphous carbon layers have been investigated by spectrophotometric means from the middle infrared up to the visible spectral region. The optical constants of the layers could be calculated by a numerical procedure which combines features of single-wavelength methods and multi-wavelength methods. Depending on the deposition technique applied, the optical constants of the layers have been found to vary over a wide range. Thus, refractive index values could be established between 1.6 and 2.9, while IR- absorption coefficients vary between 20/cm and 40,000/cm. Thus, the optical performance of the layers is nonuniform and may be influenced by selecting suitable deposition parameters. Due to the potentially wide range of optical constants of amorphous carbon, there are various possibilities for application as an optical thin film material. Applications as selective absorber coatings for solar physical purposes are discussed as well as applications as mechanically and chemically resistant and anti-reflection coatings on high-refractive index semiconducting materials (silicon, germanium).

The antireflection coating design on GaAs for the spectral range from 8 micrometers to 12 micrometers is discussed. Based on the comprehensive search technique the best systems of up to 5 layers of ZnS and Ge are presented. To get better antireflection effect the materials with lower refractive indices are needed. Utilization of yttria for this purpose is suggested and optical constants in IR for both evaporated and sputtered layers are established. Though evaporated yttria layers exhibit relatively high absorption in the region of our interest, sputtered films are much better and several systems of up to four layers of Y₂O₃, ZnS, and Ge are computed by the comprehensive search technique again.

To extract the extinction coefficient k at 10.6 micrometers of thin films or bare substrates, we present new data analysis of photo thermal measurements. We successively show how to obtain k using analytical formulation taking into account substrate absorption and how to minimize experimental errors. Then we discuss accuracy and reliability for substrates, thin films, and mirrors. Results are given for k values as low as 10^-4 for thin films, 10^-8 for substrates, and mirror reflectivities higher than 99.8% have been measured.

The specific behavior of optical thin films very often leads to limitations of optical system performances. It is necessary to have very accurate characterization techniques of the films to get a chance to understand this behavior. Characterization techniques based on the study of the propagation of guided waves in the thickness of the coatings appear to be very efficient. We describe the means we developed in that way to determine the refractive indices and the thickness of our thin films even if they are anisotropic. Guided wave techniques are sensitive enough to detect slight variations of the optical constants of thin films, so we use them to study the variations of refractive index versus temperature. From this study we obtain the thermorefractive coefficients (delta) n/(delta) T of our layers. Still with guided waves techniques, we can obtain, in some cases, the nonlinear index coefficient. We also measure guided waves attenuation and laser damage threshold with a numerical imaging system. These means, dependent upon guided waves, are used together to carry through a comparative analysis of TiO₂ and Ta₂O₅ layers made by different deposition techniques (conventional evaporation-condensation, IAD, Ion Plating).

Total integrated scattering measurements ((lambda) equals 632.8 nm) and scattering spectroscopy from the VIS to the UV region are used to investigate oxide and fluoride single layers as well as multilayer coatings for laser applications. When examining single layer films, information on fundamental scattering phenomena can easily be derived. Appropriate substrate-film designs enable volume scattering of the single layer to be separated from interface scattering. So conclusions can be drawn with respect to both roughness correlation properties and film morphology.

For obtaining thermally resistive and stable high-index materials, Ta₂O₅ films from a noble starting material of Ta₂O₅ + Ta (7 wt% added) have been developed, considering the analogy established in the case of TiO₂ films. The related optical (refractive index and absorption) and stress properties both of Ta₂O₅ and TiO₂ films are reported.

With inventions of ultra low loss glass fibers and reliable semiconductor lasers, the current choice for the telecommunication industry is lightwave technology which consists of many optical components. The reliability requirements of optical coatings used in such optical components of current and future lightwave telecommunication systems are presented in this paper.

Economical multiplexers-demultiplexers can be made from cut optical fibers coated at their ends with multidielectric filters and then put together. An optical multilayer deposited at the end of a fiber has a spectral response which is different from that obtained when the multilayer is classically used in oblique incidence. We show that it is possible to forecast the multi- demultiplexer performances on multimode fibers with a numerical model using a divergent beam of angular width `a' at a mean incidence `i.' As we know the design of the multilayer used, we can correctly predict the cross-talk and the losses of multi-demultiplexers. Then we show how a series of different experiments are exploited for this study. Nevertheless, the development of a higher selectivity spectral filter and the use of a single mode fiber necessitate further improvement concerning the test for the validity of the model used.

High average power laser systems require optical components with increasingly higher performances: high laser damage resistance, high reflectance or transmittance. We report here some results obtained with TiO₂/SiO₂ and ZrO₂/SiO₂ low losses mirrors designed for copper vapor lasers. Very low losses (40 ppm) are obtained with TiO₂/SiO₂; losses down to 400 ppm and laser damage thresholds up to 35 kW/cm² are obtained with ZrO₂/SiO₂.

In the thickness range 50 nm - 500 nm at substrate temperatures of 300 K, 375 K, and 575 K the structure of physical-vapor-deposited magnesium, lanthanum, calcium, and lithium fluoride films were investigated using TEM microfractographical replication technique. Two growth groups, columnar and granular growth, were found and main structure building elements with their characteristic medium size have been determined. Using SIMS, SNMS, RBS, and partially spectroscopical and gravimetrical measurements, the O and C contamination of the films has been investigated. The quantitative results were related to the characteristic structure building elements.

The deposition of high-reflecting dielectric coatings for the VUV spectral range requires the use of fluoride materials because oxide layers show high absorption losses at wavelengths below 200 nm. As shown in a previous paper, the reflectances of fluoride mirrors deposited conventionally are limited by volume and interface scattering due to the columnar microstructure of the layers; reduced scattering was observed in layers deposited by IAD or IBS. In these processes, oxygen was used as a reactive gas to compensate for the fluorine deficiency caused by preferential sputtering during deposition. The resulting oxide content in the layers, however, leads to high absorption losses at wavelengths below 200 nm. To obtain layers with improved stoichiometry by using IAD or IBS, these processes were performed with fluorine as a reactive gas. Single layers and high-reflecting quarterwave stacks were deposited and investigated. Their optical properties are compared to data obtained for conventionally deposited coatings and for coatings deposited by IAD or IBS using oxygen as a reactive gas. The results indicate that the ion processes are promising tools for the deposition of low-loss dielectric VUV mirrors.

The laser damage thresholds (LDT) of optical coatings lie, as a rule, markedly below those of the respective bulk materials. This is due to diverse specific real-structure properties which depend in a highly complex and sensitive way on deposition conditions. With evaporated or sputtered coatings as an example, some correlations between structural thin film properties and the LDT are discussed with concern to a further increase of the damage resistance.

The temperature distribution in optical coating was investigated. An idea about temperature field design of optical thin film is presented here. The peak temperature can be reduced and the damage threshold is improved by advanced coating design. The thermal process in optical coating irradiated by laser pulse was investigated with photothermal deflection technique. It was confirmed that the photothermal deflection technique is a very useful method for in-situ research of temperature process and damage process induced by laser pulse. Some experimental results of laser induced damage in optical coating, such as the spotisize effect, accumulation effect, effect of absorption on damage threshold, coating thickness effect, and so on, are presented in this paper.

A procedure is described for the design of quadrilayer structures which enhance the polar Kerr effect in magneto-optic recording media. An essential feature of the method is a systematic approach enabling phase-optimization to be achieved resulting in the elimination of the undesirable effects of parasitic Kerr ellipticity. Examples are presented based on the Co/Pt superlattice and amorphous TbFeCo. The spectral and angular performance of fabricated devices is compared with theory.

Recently, a lot of magneto-optical (MO) thin film media composed from an active MO film and some other dielectric and metallic films, used for optimization of MO response, were suggested. Practical realization of such complicated systems also requires the possibility of ex- post characterization of the prepared sample in the sense of determination of exact film thicknesses and/or optical constants. In this paper we discuss ellipsometric data obtained on a sputter deposited system ZnS/TbFeCo/ZnS/Al/glass in a spectral region 350 - 800 nm and angle of incidence 50 - 85 deg (step 2.5 deg). We used null ellipsometer Rudolph 436 equipped by a set of interference filters and computer software enabling simultaneous calculation of sample characteristics from angle of incidence and spectral dependent measurement. Using other pieces of information -- in our case normal reflectivity and RBS measurement -- proved to be very fruitful. Complexity of the system under discussion (at least three, more or less absorbing, films on an absorbing substrate) is further enlarged by chemical properties of individual films -- high reactivity of Al and TbFeCo and complicated deposition of stoichiometric ZnS can be noted as examples.

Reported here are studies about the thermal and laser induced metastable phase formation in amorphous GeSb₂Te₄ thin films prepared by rf-magnetron sputtering. The general structural properties of this most promising optical phase change recording material are discussed from the point of view of fast structural phase transformation.

In this review, we present some of the salient aspects of materials and design issues of phase- change and magneto-optical thin film media for erasable and rewritable optical recording. Recent developments to optimize the performance of these devices are discussed.

Color properties of a multielement optical lens are usually described by a color formula which depends on lens design, optical properties of materials, and transmission coefficients of applied AR coatings. If color properties are of importance in lens design we receive a multicriterion optimization problem. To solve the problem one can use a special choice of coatings from the available coatings set and change continuously some AR coatings parameters also. The user-friendly software was expanded, which allows simultaneous optimization of color and transmission properties of modern multielement optical lenses.

Infrared focal plane arrays (IRFPA) for staring imaging applications are now in advanced research and development stages. They offer spatial resolution in the focal plane. If spectral resolution is also required as for spectroscopic or analytical applications, a wavelength selection device is needed. The planar integration of different infrared interferencial filters on a single substrate, eventually the focal plane of such systems, would permit the obtention of arrays with spectral resolution in the focal plane and no moving parts. In this work the different aspects arising in the integration process of different IR optical multilayers on a single silicon substrate are discussed. From the experimental results of the performed works the feasibility of the proposed multispectral arrays can be derived.

A well known problem in color TV is the color shading which means a different reproduced color as a function of the position on the screen. This effect results mainly from the angular dependence of the interference layers deposited onto beam splitter prisms. We developed a software which enables us to calculate the relative signal intensities in the three channels Red, Green, and Blue. We use data of the angular dependent spectra of dichroic layers as well as data of the optical system. The influence of different layer systems and trimfilters onto color shading was calculated; the possibility of realizing these layer systems is discussed.

The image quality degradation due to atmospheric turbulence is one of the main limitations for imaging, laser propagation, and communication through the atmosphere. Adaptive optics is a technology to overcome these problems by real-time phase compensation. The main components for such systems, like wavefront correctors, wavefront sensors, and dedicated computers are existing and complete systems have been successfully tested. This article describes the principles of adaptive optics and concentrates on its applications to astronomical imaging, including some first observing results. The performance in image quality which can be expected from adaptive optics and the requirements for its application are discussed.

The relationship between the speotral responee oharacteristios of some two or three component dielectric systems and optical thicknesses and refractive indices of the layers are discussed. A solution of the problem of suppressing the high reflection zone at the fifth harmonic frequency, while maintaing high reflection at the operating frequency, is proposed for the non-equal thick two component multilayer system. Also are considered the characteristics of the three component systems ensuering high reflection on the operating wavelenght at a high transmittance in the broad spectral region including the frequency bands of the second and third haronics.

A type of narrowband interference filters for use in the UV-B-spectral region has been developed. The filter is marked by an extremely narrow bandwidth of about 2 nm, good rejection on both sides of the pass band, and high peak transmission. Care has been taken on the stability of the spectral characteristics of the interference filters against changes of environmental conditions by using only stable oxide thin-film materials. The filter performance achieved allows its use for the development of sensitive and specific instrumentation for environmental, climate, and meteorological research.

Continued development of multi-layer dielectric mirrors for applications such as laser gyroscopes shows that the highest quality of optical coatings is still produced by using ion beam sputter deposition. In this technique, a broad-beam ion source is used to sputter coating material off a metallic or dielectric target onto the substrates. Dielectric mirrors with total losses of < 40 ppm are now easy to achieve, and figures below 2 ppm can be managed. These coatings are also used for high power laser mirrors, but are only just starting to be used for other more general applications. In this paper we explain the principles of the technique, and describe the aspects of system design that we have evolved to make these coatings commercially available. We describe the results that we have achieved, particularly with SiO₂ and TiO₂ coatings. Finally, we attempt to explore the possible applications and design limits of the technology.

Porous structure and outer surface, electronic structure and cluster composition of diamond like films in dependence on film thickness are described. Transparence in the 0.3 - 25 micrometers region, corrosion resistance, and microhardness are also investigated. Diamond like films were obtained by different plasma-ion methods. The thickness of the films covered the range from 3 to 50.0 nm. The thickness of separate layers in multilayer structures was 5.0 - 10.0 nm. It has been shown that multilayer protective coatings based on (alpha) -C:H films allows the user to decrease summary thickness of the coating to raise beam resistance in comparison with one layer coatings in 1.5 - 1.8 times. Service life of a mirror with protective coatings is no less than 3 times more than for mirrors without protective coating. When changing properties and thicknesses of layers in multilayer coatings selective reflection multilayer mirrors and one-layer steering mirrors for the soft x-ray region have been created.

A sharp spectral rise in reflectance or transmittance of a suitable thin film filter can be used to construct a thermo-optical controllable mirror or phase retarder. A Fabry-Perot filter or a (lambda) /4-multilayer stack are such devices. Because of its comparatively high temperature dependence of refractive index Germanium is used as the active substance. The design wavelength is 10.6 micrometers . Reflectance of the filter can be tuned either in a quasistatic way by temperature variation of the whole device or in a dynamic regime with light pulses of visible spectral range which are strongly absorbed in Germanium. This increases temperature and causes a transmission change by displacing the resonance peak of the Fabry-Perot. Thermal relaxation time is of about 10 microsecond(s) .

Laser mirrors with dependence of phase or amplitude of reflected light on polarization under normal light incidence are proposed. Such a mirror is a combination of anisotropic element and dielectric multilayer. A metal grating of small period is suggested to use as an anisotropic element. Results of calculation and experimental testing of polarization-anisotropic mirrors are presented.

Determination of optical constants of thin films on thick substrates is discussed. The level of information contained in ellipsometric measurements is investigated. The parameters of the most important contribution to the ellipsometric data are selected. An attempt to explain the difficulties of solution of the inverse problem in ellipsometry is carried out.

Photothermal displacement microscpy was used for the characterization of Zr02 and MgF2 single-layer thin films with respect to inhomogeneities of the absorption at X = 514nm. Images are presented for X/2, X, and 27 films on BK7 glass and SQl quartz substrates. Applying modulation frequencies ranging from 1kHz to 100kHz a lateral resolution of sveral microns could be obtained. We found that size and density of the absorption inhomogeneities as well as absorptivity strongly depend on the fabrication process and weakly on substrate material, no dependence on thin film thickness was found. It is shown that the apparent defect density varies with the modulation frequency demonstrating the capability of the photothermal method to discriminate between absorptions in various depth of the thin film system. Defect densities derived from the phtothermal measurements are related to results from total integrated light scattering (TIS) experiments performed on various samples at X = 632nm. TIS amplitudes for MgF2 films on glass substrates were about one order of magnitude smaller than those from films on quartz. The latter revealed strong large scale (1mm ) variations of the light scattering amplitude what is in accordance with the absorption measurements

The inhomogeneity of single layers of ZrO₂ and MgF₂ and dynamic characteristics of these films before and after the exposure to ambient atmosphere have been analyzed using structural models and a rapid scanning spectrometer.

Temperature distributions of Ti02 single layer irradiated by iOns, 1. 06 m wavelength laser pulse were calculated with thermal transfer equation. Following conclusions were obtained: To improve thermal parameters of coating can reduce the peak temperature obviously; The thermal parameters of substrate have little effect on temperature response of coating; Temperature distribution of thin film depends on the electrical field distribution, The peak temperature of quarter -wavelength coatings is lower than that of half-wavelength coatings.

This article reviews the experimental works dedicated to the development of mirrors and antireflecting coatings for the UVspectrum range carried out in the Quantum Radiophysics Division of P.N Lebedev Physical Institute, Russian Academy of Sciences The methods of obtaining the single-layer anl multilayer optical coatings are given. The effect of the optical coating construction as well as various technological factors of coating process on damage threshold and chemical stability of mirrors is investigated

HfO₂, Y₂0₃, and Sc₂O₃ thin films and multilayer systems in combination with SiO₂ as a low index component were deposited by laser beam evaporation. Absorption was measured by photothermal displacement spectroscopy at the wavelength of 1060 nm, whereas laser damage thresholds were determined at 248 and 1060 nm. Relations between laser damage, absorption, and thin film preparation are investigated.

The envelopes along the maxima and minima of the interference spectrum of a dielectric layer on a transparent substrate are often used to determine the optical constants of the layer. The envelopes are usually drawn by hand which can lead to significant calculation errors. An optimized algorithm is proposed for computer drawing of the two envelopes for transmission and reflection spectra with interference. The envelopes are drawn for several model cases and for an experimental spectrum.

Various processes can generate energetic particles suitable for thin film deposition. In some more commonly used energetic deposition processes, auxiliary ions bombard a growing film, or evaporated coating material is ionized and accelerated toward the substrate. Ion assisted deposition (IAD), ion beam deposition (IBD), ionized cluster beam deposition (ICBD), and reactive low voltage ion plating (RLVIP) are such processes. Coating material species can be ejected also from a solid target at high velocity, for example, in ion beam sputtering (IBS). These processes generate an average energy per deposited particle that is significantly higher than for thermal or electron beam evaporation (where it is only approximately equals 0.1 eV). Higher energy results in higher surface mobility and, in turn, higher density of the growing films, as the condensing species can fill all or most of the available surface sites. The effect of higher particle energy (>= 5 eV) on thin film deposition is comparable to a transient liquid film formation. This is true even for highly refractory oxides if the thermal equivalent of the average particle energy exceeds the melting point of the coating material. An extension of the well-known structure zone model of Movchan and Demchishin with a Zone 4 represents the vitreous phase seen for some oxide thin films deposited with energetic particle processes.

Ion beam deposition processes were used to influence the microstructure and scattering characteristics of gold and platinum coatings. These metallic coatings were deposited onto super-polished fused silica and Zerodur substrates. They were deposited using thermal evaporation, ion assisted deposition, sputtering, and ion assisted sputtering. The microstructure of these films was characterized using an optical scatterometer, an optical profilometer, a stylus profilometer, scanning tunneling microscopy, and atomic force microscopy. We found that these metallic coatings deposited using ion beam deposition produced lower optical scattering and related surface microroughness.

All contributed solutions to the coating design problem, sent out with the Advanced Program, are presented and evaluated.

An eight-layer antireflection coating design including a buffer layer meets the specifications set for the coating design problem at the International Symposium on Optical Systems Design, Berlin, Germany, September 1992.

A report is given on the contents and the structure of ISO DIS 101 1 0 Preparation of drawings for optical elements and systems', including a comprehensive selection of important details. This future International Standard gives rules for the indication of quality characteristics of optical elements and subsystems.

In recent years a lot of efforts were made to characterize laser beams and to describe their propagation in optical systems. More than two years one working group of the International Organization for Standardization (ISO) worked in this field and has proposed a procedure to measure beam width and beam divergence1 . The Optical and Quantum Electronics Journal will publish a special issue on laser beam quality this year2. What a waste of time for a single parameter one might think. What are the problems, then? From the theoretical point of view all problems were solved more than hundred years ago3. A radiation field is completely determined by the amplitude distribution E (x,y,t) in a plane (or some other surface). By applying the well known formalisms developed by Kirchhoff, Fresnel, Rayleigh, Sommerfeld and others4 the field can be calculated in any point of the space, even for inhomogenous media with spatially varying refractive index.

Practical resolution of optical lithography is often defined as the minimum feature size which can be fabricated with acceptable depth of focus. It can be predicted by calculating diffraction image contrast in various defocused plane. However since large volume of calculation is required to know image contrast under partially coherent illumination, evaluation of optical lithography systems with regard to use of the practical resolution is time consuming and does not give us quick and clear forecast on optimum optical parameters for a given lithography specifications. In this paper, we propose an analytical and intuitive method for getting image contrast in defocused planes, by use of the theory of interference fringe formation. By using this method, relations among defocus, numerical aperture, wavelength, coherence factor and image contrast are derived analytically and these parameters can be optimized for given lithography methods, which employ not only the conventional but also various resolution-enhanced methods, such as annular illumination, phase-shift, illumination control and others.

The image quality degradation due to atmospheric turbulence is one of the main limitations for imaging, laser propagation, and communication through the atmosphere. Adaptive optics is a technology to overcome these problems by real-time phase compensation. The main components for such systems, like wavefront correctors, wavefront sensors, and dedicated computers are existing and complete systems have been successfully tested. This article describes the principles of adaptive optics and concentrates on its applications to astronomical imaging, including some first observing results. The performance in image quality which can be expected from adaptive optics and the requirements for its application are discussed.