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ABSTRACT: Applications of computational manufacturing experiments (CMEs) for selection of the most manufacturable designs among a variety of different design solutions are demonstrated. We compare design solutions with respect to estimations of their production yields. Computational experiments are performed using two simulation software tools. In the course of CMEs, we take into account all major factors causing errors in our deposition process. Real deposition experiments are in agreement with CMEs; the most manufacturable design exhibits better target performances compared to other designs.
Applied Optics 12/2012; 51(36):8677-86. · 1.41 Impact Factor
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ABSTRACT: We propose a general approach that allows one to reveal factors causing production errors in the course of the deposition process controlled by broadband optical monitoring. We consider computational experiments simulating the real deposition process as a crucial point of this approach. We demonstrate application of the approach using multiple experimental deposition runs of the selected multilayer coatings.
Applied Optics 11/2012; 51(31):7604-15. · 1.41 Impact Factor
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ABSTRACT: Several modern optical coating designs tools are discussed in the frame of a new design paradigm proposing the search not for a formally optimal solution with the lowest possible merit function value but for the most practical solution that takes into account additional feasibility demands. Considered design tools include a stochastic optimization procedure that takes into account upper and lower constraints for layer optical thicknesses. This procedure allows one to obtain multiple solutions to a design problem, which presents additional opportunities for choosing a practically optimal design. Two special design techniques involving integer optimization also take into account additional demands. The first one is aimed at designing multicavity narrow bandpass filters with quarter wave or multiple quarter wave layer optical thicknesses. It enables obtaining bandpass filters with extremely steep transmittance slopes, bandwidths of several tens of nanometers, and very small ripples in transmission zones. The second technique is aimed at covering design problems that have been traditionally solved using the theory of equivalent layers. One more technique considered in this paper is aimed at reducing the influence of noncorrelated thickness errors on design spectral characteristics.
Applied Optics 10/2012; 51(30):7319-32. · 1.41 Impact Factor
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ABSTRACT: Determination of actual parameters of manufactured optical coatings (reverse engineering of optical coatings) provides feedback to the design-production chain and thus plays an important role in raising the quality of optical coatings production. In this paper, the reliability of reverse engineering results obtained using different types of experimental data is investigated. Considered experimental data include offline normal incidence transmittance data, offline ellipsometric data, and online transmittance monitoring data recorded during depositions of all coating layers. Experimental data are obtained for special test quarter-wave mirrors with intentional errors in some layers. These mirrors were produced by a well-calibrated magnetron-sputtering process. The intentional errors are several times higher than estimated errors of layer thickness monitoring, and the reliability of their detection is used as a measure of reliability of reverse engineering results. It is demonstrated that the most reliable results are provided by online transmittance data.
Applied Optics 08/2012; 51(22):5543-51. · 1.41 Impact Factor
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ABSTRACT: We explain reasons of oscillations frequently observed in total losses spectra (1 - R - T) calculated on the basis of measurement spectral photometric data of thin film samples. The first reason of oscillations is related to difference in angles of incidence at which spectral transmittance and reflectance are measured. The second reason is an absorption in a thin film. The third reason is a slight thickness non-uniformity of the film. We observe a good agreement between theoretical models and corresponding measurements, which proves above statements on the origins of oscillations in total losses.
Optics Express 07/2012; 20(14):16129-44. · 3.59 Impact Factor
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ABSTRACT: We perform characterization of thin films and reverse engineering of multilayer coatings on the basis of multiangle spectral photometric data provided by a new advanced spectrophotometer accessory. Experimental samples of single thin films and multilayer coatings are produced by magnetron sputtering and electron-beam evaporation. Reflectance and transmittance data at two polarization states are measured at incidence angles from 7 to 40 deg. We demonstrate that multiangle reflectance and transmittance data provide reliable characterization and reverse-engineering results.
Applied Optics 01/2012; 51(2):245-54. · 1.41 Impact Factor
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ABSTRACT: We deal with design and production of optimal two-component antireflection (AR) coatings for an ultra broadband spectral range from 450 nm to 1800 nm. We demonstrate the whole design-production chain including design selection, choosing monitoring technique, coating production, and reverse engineering of the deposited coatings. At each step of this chain we provide thorough analysis on the basis of theoretical results and adequate computational manufacturing experiments. In order to produce the designed AR coatings we use magnetron sputtering deposition technique and accurate time monitoring.
Applied Optics 12/2011; 50(35):6468-75. · 1.41 Impact Factor
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ABSTRACT: Optical properties of metal island films (MIFs) can be combined with interference of dielectric coatings. A set of multilayer designs containing metal clusters reflecting different colours from front and back side of the coating was obtained by numerical optimization. The chosen designs presenting the range of feasible colours were deposited by electron beam evaporation. Spectrophotometric and ellipsometric measurements verified that the produced coatings present an excellent agreement with the optical performance calculated from the designs. Numerical optimization was verified as a useful method in designing of coatings containing MIFs. This approach can ease the implementation of metal clusters into multilayer designs and broaden the applications of MIFs.
Optics Express 12/2011; 19(25):25521-7. · 3.59 Impact Factor
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ABSTRACT: In the present study we determine the optical parameters of thin metal-dielectric films using two different characterization techniques based on nonparametric and multiple oscillator models. We consider four series of thin metal-dielectric films produced under various deposition conditions with different optical properties. We compare characterization results obtained by nonparametric and multiple oscillator techniques and demonstrate that the results are consistent. The consistency of the results proves their reliability.
Applied Optics 11/2011; 50(33):6189-97. · 1.41 Impact Factor
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ABSTRACT: Two algorithms used for the on-line and off-line characterization of multilayer optical coatings are experimentally compared using test samples produced by two different deposition processes and different monitoring approaches. One of these algorithms, called the triangular algorithm, demonstrates its superiority in all considered situations. We performed experiments with multilayer samples formed by high-density thin films, which allowed us to neglect possible errors in the film refractive indices and concentrate only on errors in the thicknesses of the layers of the produced coatings.
Applied Optics 07/2011; 50(20):3389-95. · 1.41 Impact Factor
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ABSTRACT: Optical constants of thin metal films are strongly dependent on deposition conditions, growth mode, and thickness. We propose a universal characterization approach that allows reliable determination of thin metal film optical constants as functions of wavelength and thickness. We apply this approach to determination of refractive index dispersion of silver island films embedded between silica layers.
Applied Optics 04/2011; 50(10):1453-64. · 1.41 Impact Factor
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ABSTRACT: A rigorous definition of the error self-compensation effect is provided. An existence of this effect in the case of coating production with broadband optical monitoring of layer thicknesses is investigated for several widely used types of optical coatings.
Applied Optics 03/2011; 50(9):C111-6. · 1.41 Impact Factor
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ABSTRACT: Modern design approaches enable one to construct a series of theoretical designs with excellent spectral properties for almost all optical coating design problems. Selection of a practical optimal design among a variety of possible theoretical designs becomes a key issue. We demonstrate how preproduction estimations of expected production yields can be used for selection of a practical optimal design. The question of reliability of such estimations is also addressed.
Applied Optics 03/2011; 50(9):C141-7. · 1.41 Impact Factor
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ABSTRACT: Wavelength dependencies of refractive indices of thin film materials differ for various deposition conditions, and it is practically impossible to attribute a single refractive index wavelength dependence to any typical thin film material. Besides objective reasons, differences in the optical parameters of thin films may also be connected with nonadequate choices of models and algorithms used for the processing of measurement data. The main goal of this paper is to present reliable wavelength dependencies of refractive indices of the most widely used slightly absorbing oxide thin film materials. These dependencies can be used by other researchers for comparison and verification of their own characterization results.
Applied Optics 03/2011; 50(9):C75-85. · 1.41 Impact Factor
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ABSTRACT: We present an indirect broadband optical monitoring approach based on using several witness substrates that are brought to a measurement position in a special sequence. Different witness substrates are used to monitor not groups of successive design layers but specially chosen design layers. An attractive feature of the presented monitoring approach is the ability to reliably control thin dielectric and metal layers. Considered examples demonstrate a good accuracy of the proposed approach.
Applied Optics 05/2009; 48(12):2315-20. · 1.41 Impact Factor
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ABSTRACT: A new model for the determination of group delay (GD) and GD dispersion of dispersive mirrors is presented. The algorithm based on this model enables one to process interferometric data provided by a white-light interferometer and to obtain GD wavelength dependence over a broad spectral range.
Applied Optics 03/2009; 48(5):949-56. · 1.41 Impact Factor
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ABSTRACT: The constrained optimization approach is applied to the design of quasi-rugate optical coatings. These coatings are defined as multilayers with no thin layers where refractive index profiles resemble rugate-type refractive index profiles and where spectral properties are typical for rugate filters. It is shown that all design problems that are usually solved using rugate filters can be solved successfully in the frame of quasi-rugate optical coatings. Comparison between quasi-rugate and two-component multilayer designs is provided.
Applied Optics 11/2008; 47(28):5103-9. · 1.41 Impact Factor
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ABSTRACT: A new optical monitoring system has been developed that allows recording of transmission spectra in the wavelength range between 400 and 920 nm of a growing optical coating during deposition. Several kinds of thin film sample have been prepared by use of a hybrid monitoring strategy that is essentially based on a combination of quartz monitoring and in situ transmission spectra measurements. We demonstrate and discuss the applicability of our system for reengineering procedures of high-low stacks and measurements of small vacuum or thermal shifts of optical coatings.
Applied Optics 06/2008; 47(13):C49-54. · 1.41 Impact Factor
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ABSTRACT: We deal with optimal two-material antireflection (AR) coatings for the visible and adjacent spectral regions. It has been shown before that, for a given set of input parameters (refractive indices of the substrate, ambient medium and high- and low-index coating materials, and for a given spectral width of the AR coating), such designs consist of one or more clusters of layers of approximately constant optical thickness and number of layers. We show that, through the analysis of many different optimal coatings, it is possible to derive two parameters for a simple empirical expression that relates the residual average reflectance in the AR region to the number of clusters. These parameters are given for all possible combinations of relative spectral bandwidth equal to 2, 3, and 4; low-index to ambient-medium index ratio equal to 1.38 and 1.45; and high-to-low index ratio equal to 1.4, 1.5, and 1.7. The agreement between the numerically and the empirically calculated values of residual average reflectance is excellent. From the information presented the optical thin-film designer can quickly calculate the required number of layers and the overall optical thickness of an AR coating having the desired achievable residual average reflectance.
Applied Optics 06/2008; 47(13):C124-30. · 1.41 Impact Factor
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ABSTRACT: We present an algorithm for the automatic generation of a monitoring spreadsheet that enables the most effective application of the termination level correction algorithm proposed in our previous publication. On a whole the presented monochromatic monitoring strategy entirely eliminates a cumulative effect of thickness errors in optical coating production using direct optical monitoring. The effectiveness of the new monitoring strategy is demonstrated by computational manufacturing experiments in which such error factors as instability of deposition rates, errors in measured transmittance data, shutter delays, and variations of layer refractive indices from their theoretical values are simulated.
Applied Optics 11/2007; 46(28):6936-44. · 1.41 Impact Factor
