Direct measurement of the extinction coefficient by differential transmittance
Thin films used as optical coatings have a light extinction coefficient that is barely measurable today.
Madrid / November 22, 2023
A team of researchers from the “Daza de Valdés” Institute of Optics and the “Blas Cabrera” Institute of Physical Chemistry of the CSIC and NASA Goddard Space Center has developed an innovative procedure to precisely measure the extinction coefficient for sheets of very transparent materials. The study, published in the journal Optics Express, describes a pioneering optical method that eliminates the need to assume that the material behaves following a constant optical model and knowledge of additional physical properties of the material.
The proposed method is based on the preparation of a sample with two zones, at least one of them covered with a film of the target material. By measuring the differential transmittance between these two areas, the researchers demonstrated that this difference is proportional to the extinction coefficient k of the film material, under specific measurement conditions.
The procedure requires knowing the Brewster angle of the film, which is achieved by previously measuring the refractive index of the material. The refractive index of these thin films can be easily measured using ellipsometry.
The team of researchers demonstrated the usefulness of the method by calculating the extinction coefficient in AlF3 films deposited by evaporation in the far ultraviolet spectrum. Furthermore, they analyzed the uncertainty associated with the new procedure in terms of the uncertainty of the refractive index of the film, the wavelength and the degree of polarization of the incident light, concluding that an uncertainty of 2 × 10-5 is achievable in the measurement of the extinction coefficient k.
The results obtained with this new procedure open new possibilities in the design and development of more efficient optical coatings. This innovative study represents a significant advance in the direct measurement of the extinction coefficient in transparent materials, offering a valuable tool for the research and development of cutting-edge optical applications.
Chemometric-driven quantification of construction and demolition waste using Raman spectroscopy and SWIR: Enhancing sustainability in the ceramic sector
Madrid / November 24, 2023A team of researchers from the Institute of Ceramics and Glass and the Optics Institute, both of the CSIC, has achieved...
Correlation between structure and mechanical properties in α-quartz single crystal by nanoindentation, AFM and confocal Raman microscopy
Madrid / November 7, 2023A group of European researchers has carried out a study that reveals the correlation between the internal structure and...
Unveiling the effects of the surface and in-depth nanostructure on the far-UV optical reflectance of thin fluoride multilayer coatings
Madrid / November 3, 2023Researchers from the Optics Institute of the CSIC, the Materials Microanalysis Center of the Autonomous University and the...