Prof. Alexander Quandt Profile

Prof. Alexander Quandt

at Univ of the Witwatersrand

SPIE Involvement:

Conference Program Committee | Author

Proceedings Article | 20 August 2020 Presentation

Optical topological materials and winding numbers

Alexander Quandt

Proceedings Volume 11461, 1146115 (2020) https://doi.org/10.1117/12.2567486

KEYWORDS: Systems modeling, Mathematical modeling, Photonic crystals, Waveguides

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Proceedings Article | 1 April 2020 Presentation

Simulations in glass photonics (Conference Presentation)

Alexander Quandt, Robert Warmbier

Proceedings Volume 11357, 113570V (2020) https://doi.org/10.1117/12.2557808

KEYWORDS: Glasses, Dielectrics, Photonics, Solids, Optical properties, Solar cells, Ions, Device simulation, Materials science, Systems modeling

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We will discuss the use of some of the standard methods of computational materials science to predict the optical properties of glasses. Given the accuracy of state-of-the-art ab initio methods to simulate the dielectric properties of solids, some of these methods turn out to be a viable alternative to experimental studies, and they also allow for the prediction of dielectric properties in frequency ranges, which might not be easily accessible in a real experiment. Density functional based linear response theory for example allows for the simulation of dielectric properties over a wide frequency range, related to the many-electron system of a solid. We will summarize the corresponding theoretical background, and discuss the predictions made by applying some of these theoretical and numerical approaches to a variety of glasses. Beyond the modelling of one-particle excitations that contribute to the dielectric properties of a solid, we also point out the possibility to include contributions from particle-hole excitations based on the Bethe-Salpeter equation. We will summarize the corresponding theoretical background and show some numerical examples. Additional contributions to the dielectric properties, which stem from the vibrational motion of ions in a solid, are less straightforward to implement. Therefore, our principal focus will be on a critical assessment of various theoretical and numerical approaches discussed in the literature. With respect to novel types of technological applications based on thin glass films, we will focus on the implementation of up/down-conversion process in conventional types of solar cells as mediated by the deposition of glass layers containing rare earth ions. We will point out several possibilities, where numerical rather than experimental data may become the basis of a typical solar cell device simulation. Finally, we will suggest possible methodological improvements, which also take advantage of the accuracy and the numerical efficiency of first principles approaches.