The Effect of Errors in the Optical Monitoring of Narrow-band All-dielectric Thin Film Optical Filters
TL;DR: In this paper, an approximate theory of the effects of these two types of error on turning value monitoring is developed and the results are used to devise a modification to the conventional technique which enables filter performance much nearer theoretical to be achieved.
Abstract: Errors which occur during the deposition of thin film narrow-band optical filters can be classified as either static or dynamic. An approximate theory of the effects of these two types of error on turning value monitoring is developed and the results are used to devise a modification to the conventional technique which enables filter performance much nearer theoretical to be achieved.
Citations
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TL;DR: A versatile deposition error compensation program developed at the National Research Council of Canada for the simulation and real-time control of the manufacture of multilayers composed of dielectric or absorbing films is described.
Abstract: The manufacture of complicated optical coatings consisting of many layers of different thicknesses can be a challenge, especially if the deposition technique does not produce dense layers. Deposition errors in a layer can affect not only the desired performance of a multilayer, but can also lead to a complete breakdown of the monitoring and control of subsequent layers. The best chance to achieve the desired optical performance of a multilayer involves deposition error compensation. In this process, the construction parameters of a completed layer are evaluated to determine if any deposition errors have occurred and then the remaining layers of the multilayer system are reoptimized to compensate for any errors made. This paper describes a versatile deposition error compensation program developed at the National Research Council of Canada for the simulation and real-time control of the manufacture of multilayers composed of dielectric or absorbing films. To model porous layers, an effective medium theory approach is used to relate the optical constants of the layer in vacuum and air to the microstructure of the layer. In the simulation mode, random errors are applied to the thickness and porosity of the layers and measurement errors are also included. The best monitoring strategy for the manufacture of a given multilayer is established on the basis of statistical information obtained from a number of these simulations. In this paper the results of calculations on the effectiveness of various monitoring strategies are presented for a sharp edge filter produced by three different physical vapor deposition methods. An extensive list of references to previous papers dealing with sources of errors during deposition is also provided.
104 citations
TL;DR: The goal is to attract attention to the increasing importance of computational manufacturing at the current state of the art in the design and manufacture of optical coatings and to demonstrate possible applications of this research tool.
Abstract: Computational manufacturing of optical coatings is a research area that can be placed between theoretical designing and practical manufacturing in the same way that computational physics can be placed between theoretical and experimental physics. Investigations in this area have been performed for more than 30 years under the name of computer simulation of manufacturing and monitoring processes. Our goal is to attract attention to the increasing importance of computational manufacturing at the current state of the art in the design and manufacture of optical coatings and to demonstrate possible applications of this research tool.
63 citations
TL;DR: It is shown that in the turning value monitoring of broad-band components the most important factor is the small consistent overshoot made by experienced plant operators and that, to be effective, a pre-coating must minimize the interactions between errors caused by the successive overshoots.
Abstract: Theoretical techniques which were developed for the study of errors and error compensation in the turning value monitoring of thin-film narrow-band filters are applied to the monitoring of broad-band components, especially anti-reflection coatings and edge filters. The technique of pre-coating the test plate in semi-direct monitoring is examined. It is shown that in the turning value monitoring of broad-band components the most important factor is the small consistent overshoot made by experienced plant operators and that, to be effective, a pre-coating must minimize the interactions between errors caused by the successive overshoots. Techniques for predicting the magnitudes of such interactions are given. The stability of an alternative technique for edge filters, that of semi-direct level monitoring, is considered and the way in which pre-coatings can improve the accuracy of edge position demonstrated.
61 citations
TL;DR: In this paper, a review of the problems in the production of narrow-band all-dielectric thin-film optical filters is presented, where the authors consider only designs composed entirely of optical thicknesses which are integral multiples of a quarter-wave.
34 citations
TL;DR: A new approach to choosing a sequence of monitoring wavelengths for monochromatic monitoring of optical coating production based on a preproduction estimation of expected levels of errors in thickness of layers of a deposited coating is presented.
Abstract: We presents what we believe to be a new approach to choosing a sequence of monitoring wavelengths for monochromatic monitoring of optical coating production. The new approach is based on a preproduction estimation of expected levels of errors in thickness of layers of a deposited coating. It is demonstrated that the proposed monitoring strategy reduces the effect of accumulation of thickness errors. An advantage of the new monitoring strategy becomes especially noticeable when the number of monitored layers is equal to several dozens.
33 citations
References
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TL;DR: In this article, the effects of errors in the turning value method of film-thickness monitoring on the performance of all-dielectric interference filters were studied theoretically by both an accurate and an approximate method, and it was shown that although the potential accuracy of the method in monitoring a single layer is very poor, the theoretical accuracy of peak frequency and the overall performance of complete narrow-band filters are extremely good.
Abstract: The effects, on the performance of all-dielectric interference filters, of errors in the turning value method of film-thickness monitoring, are studied theoretically by both an accurate and an approximate method. It is shown that, although the potential accuracy of the method in monitoring a single layer is very poor, the theoretical accuracy of peak frequency and the overall performance of complete narrow-band filters are extremely good. Poor performance of real production filters is therefore unlikely to be due to an inherent limitation of the method, but rather to a faulty application of it, or to other factors unconnected with the monitoring method.
131 citations
TL;DR: In this article, it is known that the optical properties of dielectric quarter-wave multilayers are stationary in relation to the thickness of each layer, and this property is particularly interesting for the purpose of controlling the production of such stacks.
91 citations
TL;DR: In this article, a simulation par le calcul sur ordinateur permet de montrer que l'influence des erreurs de realisation de chaque couche, sur le resultat final, depend du procede de controle utilise.
Abstract: Pour controler la formation de couches d'epaisseurs optiques ne egales ou multiples d'une meme valeur u0/4, on utilise couramment des methodes optiques. Il est en particulier commode de reperer, au cours de l'evaporation, pour la longueur d'onde de centrage du filtre u0, les extremums du facteur de transmission T. Mais on doit bien distinguer les extremums correspondant a T/ e=0 des extremums du profil spectral (T/u=0) observables pendant le depot de chaque couche. La simulation par le calcul sur ordinateur permet de montrer que l'influence des erreurs de realisation de chaque couche, sur le resultat final, depend du procede de controle utilise. Le reperage des zeros de T/u ne permet pas de beneficier d'une compensation des erreurs aussi exceptionnelle que celui des zeros de T/e. On souligne ainsi l'interet du choix d'un controle ‘stable’ ou l'influence des erreurs cumulatives est telle que leurs effets se compensent parfaitement. Les tolerances de realisation des filtres interferentiels sont alor...
20 citations
TL;DR: In this article, the effects of absorption on the theoretical accuracy of the turning value method of film thickness monitoring in the production of thin-film all-dielectric narrow band optical filters are investigated.
Abstract: The effects of absorption on the theoretical accuracy of the turning value method of film thickness monitoring in the production of thin-film all-dielectric narrow band optical filters are investigated. It is shown that the performance of the method is at least as good as it is in the absence of absorption, although care must be taken in the interpretation of the monitoring signals for certain critical layers.
13 citations