The manufacturing processes for spectral-sensitive on-chip masking of Si-PIN-diodes using thin-film optical filters are described. As two examples, a diode array with red, green, and blue filters (RGB) and a UV-sensitive diode are explained in detail. The RGB-filters are made of TiO₂SiO₂ thin-films and the UV-filter is a metal/dielectric multilayer using HfO₂, SiO₂, and Al thin-films. Both filter types are self-blocked over a wavelength range from 200 to 1100nm. The optical coatings on the diodes are arranged as pixels with rhombic or rectangular shapes and with a later dimensions of about 20 microns as minimum. The used lift-off technique for patterning the coatings is described briefly. Reactive e-beam evaporation with ion-assistance is used to deposit the optical coatings.

Well done designs and well equipped machines are only half the way to reproducible and stable quality of a coating production. To achieve this aim it is also necessary to have a complex production management system to one's disposal, including recipe management, machinery management and quality assurance. Most production errors and rejects are caused by wrong handling, which can be leaded back to a lack of actual information, or by errors of measurement-systems and by fails of equipment during a coating process. So, the very simple rules one has to observe are: 1.) Transfer really all necessary information about the process to operator and to machine and force the operator to read this information, by using an online-checklist during charging a batch. 2.) Never trust in a single measurement-result of your plant-equipment, without a cross-check to independent generated data's; redundancy is the magic word for process-assurance. 3.) Check the status of your equipment as often as possible; integrate a maintenance plan in your plant control and let the machine record all parameters, which are relevant for wearing parts or media. This essay will show, how to organize your recipe parameters, transfering information to plant and operator, methods for redundancy and cross-checks of parameters, and an example for a complex coating system based on a LH-A700QE.

The optical characterization of materials in thin film phase is a standard task in the field of coating technology. There are experimental circumstances where the accurate comparison between several deposition processes (for the same material) is important. In these cases, several sets of substrates are coated at the different deposition plants. The samples will be subsequently analyzed using, if the plants are at different locations, different spectrophometers and finally the results of all the optical characterizations will be compared. The aim of this work is to present the results of a global procedure for the optical characterization of LaF₃ in the UV-visible region, deposited at three different plants. We have used R and T spectrophotometric data and we have assumed the following model for the optical characterization: n(λ)=n₀+n₁/λ², k(λ)=k₀ exp(k₁/(λ). Our method characterizes all the samples from the same deposition process by a single set of parameters (instead of a set for each sample), using all the available measurements to determine them in a single numerical fitting, without a significant loss in the quality of the fittins. This procedure reduces the number of parameters and makes the comparison between different deposition processes more clear. By using similar results obtained for MgF₂ the optical characterization of stacks (manufactured using MgF₂ and LaF₃) is also presented.

We propose a design method for optical lattice filters using the Schur algorithm in the z-transform domain. The algorithm of Schur (on a power series bounded in the unit circle) is used for the one-dimensional inverse scattering problem to determine the reflection coefficients of multilayer medium modeled by the lattice filter. The proposed algorithm can also be used to determine reflection coefficients in Fabry-Perot etalons and multilayer thin film modeled by the lattice filter structure. We use the FFT method to find the transmission transfer function from transmission magnitude only. To verify the method, we give three simple examples.

Transparent conductors find applications in electrodes for flat panel displays, electromagnetic shielding, optical filters, antennas embedded in windshields, transparent electrodes for light-emitting diodes and lasers. Shields transparent in the atmospheric spectral windows of (3- 5)μm or (10-12)μm are in demand for electromagnetic protection of infrared displays in thermo-imaging devices. We propose semiconductor/dielectric or metal/dielectric multilayers that can serve as shield against RF and microwave radiation, while being transparent in the mid-infrared spectral region.

Optical fiber communication involves the transmission through a fiber of an optical signal consisting of a carrier with superimposed information. The bandwidth of the optical signal is only a small fraction of the wavelength region that an optical fiber is capable of transmitting. The volume of information can therefore be increased by adding further simultaneously transmitted carriers of wavelengths sufficiently separated to avoid overlapping bandwidths - a process known as wavelength division multiplexing. The available wavelength region for each individual carrier is known as channel and the ability to combine and separate the signals carried by the various channels is an important system feature. Drop, add, multiplexing and demultiplexing are terms used to describe such operations, and narrow-band thin-film filters arranged to transmit one channel and reflect all others are ideal beam splitters for these applications. Thin-film narrow-band filters have a long history and are well understood. The basic principles involved in narrow-band filters for wavelength division multiplexing are, therefore, not new. What is new is the unprecedentedly high level of performance demanded by the application. Meeting these demands has required entirely new approaches to design, manufacture and testing of the components, currently operating in the near infrared around 1550nm. Even the terminology, such as insertion loss and crosstalk, breaks with tradition. Center-wavelength precision, peak transmittance and residual reflectance levels, uniformity, and environmental stability all present special challenges. In spite of all this such filters are being successfully designed and manufactured. This paper reviews the fundamental problems.

The success of volume production of 200GHz and 100GHz spacing WDM band pass filters relies on several critical issues: (a) a robust, high tolerance design; (b) optimized machine configurations; (c) a stable and repeatable process; and (d) an accurate and reliable optical monitoring system. At Corning NetOptix, significant effort has been made to optimize the chamber and process parameters in order to control the optical performance, the reproducibility and the useful area. This results in increased production yields and excellent filter performance. The results of 200GHz and 100GHz spacing WDM filters manufactured at Corning NetOptix are presented.

Filters for Wavelength Division Multiplexers with very straight slopes and virtually no ripple are designed. Filters for DWDM applications are shown with the simplest improvements. Filters designed with a variety of recipes that give similar results are analyzed for broad band seven cavity types. All the recipes use "Quarter-wave designs only" to simplify manufacturing. Filters with very broad bandpasses are designed. These filters use equivalent refractive indices for matching the admittance of the general filter to the environment that it is in. More than 14 cavities are possible. These are much sharper than typical long pass filters of the same blocking density.

The use of colored glasses for protecting the art works exposed to natural lighting in museums, galleries and exhibitions is investigated. A color fading has been measured on paintings as a consequence of the ultraviolet and visible radiation that falls on the object surface. The problem of damage arises also with artificial lighting, in this case the emission spectrum has a large component in the near infrared. The role of thin film coatings in preserving paintings from ultraviolet, visible and near infrared radiation damage is examined.

In this paper, a graded Si_1-xGe_x buffer and thereafter the Si_0.8Ge_0.2 uniform layer were grown at a little lower temperature to keep the surface smooth, which will provide the gliding dislocations a wider channel and less low energy nucleation sites on the surface. Therefore, the dislocation density may be reduced. However, the motion of the existing threading dislocations cannot retain equilibrium at lower temperature, strain will accumulate and be in favor of the nucleation of dislocation. In situ annealing was used to reduce the residual strain in the sample during the low-temperature growth of SiGe. A fully relaxed Si_0.8Ge_0.2 layer was obtained with the surface dislocation dnesity of 3x10⁵cm^-2.

Coating of plastics for optical applications is mostly intended to improve their mechanically durability and to provide a desired optical function. A potential layer system to realize an antireflection function and to improve the mechanical properties simultaneously in a combination of hard coating SiO₂ with classical 4-layer antireflection system consisting of SiO₂ and Ta₂O₅. Plasma-Ion Assisted Deposition (Plasma-IAD) at room temperature has been applied for coating experiments on PMMA and Polycarbonate. The temperature on a polymer substrate can reach a critical value in respect to its low thermal stability, if thick layers Ta₂O₅ have to be deposited. The increase of temperature is mainly determined by the radiation heat of electron beam evaporator. With needle optimization, an alternative coating design has been developed. The design is characterized by low thickness of high refractive index layers, which add up to less than about 5% of the total multilayer thickness. The high refractive index layers are almost evenly distributed over the whole stack. The total thickness of this kind of coating is adjustable between 800 nm and about 2600 nm. The mechanical properties of the coating deposited on plastics corresponds to that of a single SiO₂ laser of the same thickness.

In the course of the rapid development of laser technology and modern optics, an ever increasing demand for optical coatings with extraordinary specifications can be observed. In practice, the production of such high quality optics with special requirements in respect to bandwidth, edge steepness or wavelength accuracy regularly requires an extended optimization of the coating process. In many cases, the resulting high production cost delays the development of new promising concepts in laser and optics technology. For the realization of new optical designs, generally two difficulties occur: At first, the physical properties of the coating materials change after completion of the coating process due to environmental influences. Furthermore, the accuracy of the commonly utilized methods for thin films thickness monitoring is not sufficient for a reliable thickness control. In this paper, an ion beam sputtering (IBS) coating process is described for the completely automated fabrication of optical coatings with extremely stable characteristics. In contrast to conventional arrangements with witness glasses, the presented thickness monitoring during the coating process can be directly performed for the optics. The precise transmittance measurement over a bandwidth of one octave is achieved by a fiber-coupled multi-channel spectrophotometer. With this arrangement also very small layer thickness errors are detected and may be compensated by optimizing the subsequent layers in the stack in order to meet the specifications. The combination of the innovative IBS- process with the broad-band spectrophotometric thickness monitoring is the key for new laser applications, e.g. low loss edge filters for high power diode laser wavelength multiplexing or phase-optimized mirrors for ultrashort pulse laser systems.

Multilayer dielectric systems find wide employment in different fields of science and engineering. Dielectric systems, formed by layers with small absorption, attract particular interest. Value of absorption, as a rule, depends on structure of the system (order and optical thickness of layers), angle of incidence and wavelength of radiation. Experiment shows that there are peaks of absorption on certain angles of incidence and wavelength, but behavior of absorption wasn't studied well. Model of a system, formed by isotropic layers settled on semiinfinite substate proved to be a good approximation for many of real optical systems. We studied pecularities in spectral dependencies of reflection, transmission and absorption coefficients in dependance on the angle of incidence and wavelength of falling radiation with flat wave front. Problem was solved on the basis of Maxwell equations and corresponding boundary conditions.

We report here on a novel optical thin film monitoring technique. The instrument has been developed to improve the spectral performance of multilayer stacks by monitoring the instantaneous spectral performance over a wide wavelength band. Use is made of two commercially available miniature fibre spectrometers to cover the band 200 nm to 1 μm. A special software program has been written to read in the data from dual spectrometers and display the data to the monitor. For each layer, the real time data is compared to a calculated spectral performance to assist with the correct film thickness termination. The system stability is assisted by continuous referencing of the lamp emission spectrum. Very complex multilayers can be reliably deposited using the technique.

The presented work demonstrates that powerful laser radiation causes changes in absorbance spectra of epoxy resin and polyethylene. Thin polymer films were located between infrared AgBrCl optical fibers and exposed to the radiation of CO₂ laser. The outpot of the laser source has been varied in the range 0-8.5 Wt. Absorbance spectra were measured by FTIR spectrophotometer. It was revealed that characteristic absorbance peaks of polymers decay under the powerful IR light. The apparent dependence of peak magnitude on IR radiation power has been established. The mathematical theory of the observed effect was worked out. Authors suggested that the effect under discussion is caused by oxygen-free thermal action of IR radiation on the chemical structure of polymer materials. The revealed effect could be effectively used for the lowering of losses in adhesive contacts of IR optic elements. The novelty of the proposed method lies in the fact that thermal treatment is localized strictly in adhesive contact, optical elements to be contacted (fibers, lenses, etc.) which are highly transparent in IR don't experience the IR radiation, but polymer adhesive is subjected to a temperature rise.

Plasma polymerized hexamethyldisiloxane (PP-HMDSO) thin films have been obtained in a DC glow discharge from oxygen/HMDSO gas mixtures. Such films are successfully applied to the pr otection of Al metallisations on plastic substrates. The composition of the films (SiO_xC_y:H) may be varied from organic (polymer-like) to inorganic (SiO₂-like) by varying the oxygen-to-monomer ration in the precursor gas mixture. The structural and functional properties of the films are studied as a function of the plasma parameters.

A genetic algorithm (GA) with adaptive mutations has been employed for the design of Bragg reflectors. The algorithm enables three different design types a) composition and thickness of two layers are chosen and the pair is repeated b) two compositions are chosen for the two alternating materials, and thickness of each layer is optimized c) composition and thickness of each layer are optimized. In all cases, the wavelength and composition dependence of the index of refraction is taken into account. Also, it is possible to impose constraints on the composition difference of the neighbouring layers, either with a penalty function or with narrowing the boundaries for possible compositions. This feature is important because the large lattice mismatch between GaN and A1N can cause poor surface morphology, so measured reflectivity would be lower than the calculated one due to the surface roughness. The algorithm enables finding the optimal design for two chosen incident and final media, and it is capable of taking into account the existence of a finite, optically thick substrate. We have investigated two systems: air/sapphire/A1_xGa_1-xN reflector/GaN and GaN/A1_xGa_{1- x}N/air.