ZnS and ZnSe interference filters exhibit fast switch‐on times (10 and 50 μs, respectively) with milliwatt powers at room temperature The nonlinearity in the refractive index is found to result from heating by absorption Crosstalk between two light beams is negligible for separations exceeding 20 μm with 77‐μm beam diameters

Microsecond room-temperature optical bistability and crosstalk studies in ZnS and ZnSe interference filters with visible light and milliwatt powers

First, an introductory review of deposition-dependent microstructural peculiarities of real optical thin films is presented. Then, some physical and chemical properties of particular interest for the user of coated optical elements are surveyed. Of the optical properties, the refractive index is discussed in detail, and reflectivity, light scattering, and surface plasmon excitation are also included. Of the mechanical properties, adhesion, hardness, abrasion as well as some aspects of intrinsic stress are illustrated with practical examples. The importance of the thermal stability of optical coatings is emphasized, and some examples of severe alterations of coating properties after thermal treatment are given. The degradation of coatings as a result of radiation impact is also treated briefly. Finally, the discussion of diffusion processes within some coatings and in the surface region of substrates leads to a survey of selected chemical reactions between the substrate and the coating, within the coating itself, and between the coating and the environment.

Physical and chemical aspects in the application of thin films on optical elements.

Thin film narrow band optical filters

The optical properties of thirty-five all-dielectric spectral filter coatings for the visible spectrum have been investigated and correlated with the deposition conditions of the constituent layers of cryolite and zinc sulfide and with the processes which occur when the coatings are exposed to atmosphere. It will be shown that the results of measurements of transmittance and reflectance over the passband wavelengths can be predicted theoretically only if account is taken of absorption in the layers and scattering at the rough boundaries and of changes in the refractive indices of the layers due to water penetration.

Optical properties of narrowband spectral filter coatings related to layer structure and preparation

Thin films are applied to effect a desired change in chemical and/or physical properties of glass and plastic surfaces. Glass containers such as nonreturnable and returnable bottles, conventional, and light-weight are coated by CVD and spray processes with various metallic oxides such as tin oxide, and are given topcoats such as nontoxic silicones, various waxes, and glycols. The thin invisible oxide film is deposited generally by the application of a hot-end coating after the containers leave the forming machine, and before they enter the annealing lehr. The organic coating, known as a cold-end coating, is applied over the oxide film at a lower temperature when the glass containers emerge from the lehr. Protection from friction damage is essential in modern filling lines where speeds of up to 800 bottles min –1 are used. Thin vitreous coatings of SiO 2 , TiO 2, and ZrO 2 deposited by precipitation from solutions, and suitable for a variety of technical glass applications, can also be used to protect ancient glasses against weathering. Moisture-sensitive optical components, such as alkali metal halide materials, require protection against exposure to high humidity. In addition, they need antireflective surface properties. With plasma polymerization, pinhole-free, highly adherent, mechanically intact fluorocarbon-type polymer films in the thickness range between 500 and 1500 nm can be obtained.

Application of Coatings on Glass

For narrow-band interference filters, we generally observe a small variation of peak wavelength with time; this variation of filter characteristics depends to a large degree on the materials of which these filters are made, and on the manufacturing process. Several explanations have been given to take account of this effect, which is particularly dramatic in the case of very narrow-band filters, so it is of the utmost importance to study in detail the influence of parameters such as the shift of temperature within the plant during deposition. The aim of this work is to know how to produce filters whose optical characteristics are steady with time. A significant advance in the study of this problem has been obtained by simulating the monitoring process on a computer. However, it is necessary, for each material used, to determine the dilatation coefficients of both refractive index and thickness. In this work we show how these coefficients may be deduced from measurements of shifts with temperature of the p...

Influence of Temperature on the Optical Properties of Narrow-band Interference Filters

Computer simulation of thin-film multilayer production has shown that the effects of errors in the layers on the performance of complete coatings depends strongly on the particular monitoring process used. Deposition of dielectric quarter-wave multilayers is usually controlled by a method which involves the detection of the maxima and minima of transmission for the centre wavelength of the filter, the turning value method, and we know that this technique profits from an exceptionally efficient error compensation. The true tolerances in stack production are much larger than we would calculate neglecting this compensation. However, the analysis of experimental results shows that we must consider other effects which have so far been neglected in the computer simulation and which affect the monitoring process enough to prevent the fabrication of interference filters with very narrow transmission bands. Here we describe how the computer simulation is modified to take account of the influence of temperature cha...

P. Roche

Papers

Influence of Temperature on the Optical Properties of Narrow-band Interference Filters

On the Limiting Bandwidth of Interference Filters : Influence of Temperature during Production

Influence of temperature on the optical properties of narrow band interference filters