Michael A. Kokarev

Effect of systematic errors in spectral photometric data on the accuracy of determination of optical parameters of dielectric thin films

The determination of optical parameters of thin films from experimental data is a typical task in the field of optical-coating technology. The optical characterization of a single layer deposited on a substrate with known optical parameters is widely used for this purpose. Results of optical characterization are dependent on not only the choice of the thin-film model but also on the quality of experimental data. The theoretical results presented highlight the effect of systematic errors in measurement data on the determination of thin-film parameters. Application of these theoretical results is illustrated by the analysis of experimental data for magnesium fluoride thin films.

Key role of the coating total optical thickness in solving design problems

A key role of the design total optical thickness in the synthesis process is demonstrated by practical examples and confirmed by rigorous theoretical results. A special development of the needle optimization procedure called the synthesis by gradual evolution is proposed. This synthesis process does not require any starting design. It automatically constructs a set of designs with various combinations of three major design parameters: merit function value, number of design layers, design total optical thickness. This provides the optical coating engineer with additional opportunities in choosing the most practical design.

Indirect broadband optical monitoring with multiple witness substrates

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.

Optical Characterization of Thin Metal Films

The origin of difficulties connected with optical characterization of thin metal films is theoretically explained. A methodology of optical characterization that can raise accuracy of determination of optical parameters of thin metal films is proposed.

Reverse Engineering of Fabricated Coatings Using Off-Line and On-Line Photometric Data

We propose an approach to the determination of thicknesses of individual coating layers from on-line monitoring data. We demonstrate an application of this approach to the analysis of the 52-layer filter.

Phase properties of WDM filters

A simple relationship between the radiant energy transmittance and group delay in the passband region is established. This relationship is based on the consideration of complex poles of the amplitude transmittance.

New optimization algorithm for the synthesis of rugate optical coatings

By comparing multilayer and rugate solutions to a typical rugate synthesis problem we demonstrate that rugate synthesis methods are still of a great importance. The new accurate algorithm for the synthesis of rugate coatings with arbitrary refractive index profiles is discussed. It is shown that this algorithm can be successfully applied for solving such classical rugate synthesis problem as reducing sidelobes accompanying stopbands of rugate filters.