The refractive index is a fundamental optical constant of matter, required for the design of each and every photonic device. The refractive index exhibits global dependencies on frequency and temperature, as well as spatial dependencies with respect to i) sample’s topology, in the presence of inhomogeneity and ii) incidence’s wave polarization and propagation direction, in the presence of optical anisotropy. In general, it is a complex quantity, the imaginary part of which incorporates light attenuation effects (absorption, scattering) and vanishes only for optically transparent media.
Established methods for measuring the refractive index of transparent samples rely on refractometry, ellipsometry, or interferometry approaches. These methods come up with variable operational specifications in terms of accuracy, complexity, tolerance to sample quality, etc. However, they all share a common limitation: error in refractive index measurement increases with increasing light absorption or scattering. The attenuation-induced error is intuitively acknowledged by researchers in the field, but its unambiguous determination – let alone correction – remains an elusive task.
We aim to discover and validate analytical procedures that will enable the accurate calculation of the complex refractive index of attenuating media, from experimental data of the angle-dependent Fresnel reflectance at a prism/sample interface. This line of research will provide directions on the design of future refractometers and expand their use to new application areas.
Group’s journal publications on this topic [click for more]
17 S. Koutsoumpos, P. Giannios, K. Moutzouris. Critical angle refractometry with optically isotropic attenuating media. Applied Physics B 128, 91 (2022).
15 S. Koutsoumpos, P. Giannios, K. Moutzouris. Critical angle refractometry for lossy media with a priori known extinction coefficient. Physics 3, 569 (2021).
14 S. Koutsoumpos, P. Giannios, K. Moutzouris. Extended derivative method of critical-angle refractometry for attenuating media: Error analysis. Measurement Science & Technology 32, 105007 (2021).
12 S. Koutsoumpos, P. Giannios, I. Stavrakas, K. Moutzouris. The derivative method of critical angle refractometry for attenuating media. Journal of Optics, 22, 075601 (2020).
11 S. Koutsoumpos, P. Giannios, D. Triantis, K. Moutzouris. Critical-angle differential refractometry of lossy media: a theoretical study and practical design issues. Instruments 3, 36 (2019).
Group’s conference publications on this topic [click for more]
Pending