Optical spectroscopies are emerging as powerful and exquisitely sensitive tools to probe surfaces, with many potential applications in determining surface structure or monitoring the growth of materials. However, the interpretation of surface optical spectra is not at all straight forward and may even be counter-intuitive. It requires either comparisons of with already understood spectra for similar structures or detailed calculations of the line shape. Unfortunately, such calculations are very delicate and computationally demanding. They have therefore seldom been helpful in understanding and predicting the surface optical response.

However, thanks to theoretical and computational progress in the last couple of years, it has now become possible to calculate surface optical spectra accurately and with true predictive power. On one hand, this allows for a much better understanding of the origin of specific features in spectra. On the other hand, a good agreement between the measured and the calculated spectra offers conclusive confirmation of the surface structure.

In this talk I will focus on the simulation of Reflectance Anisotropy Spectroscopy (RAS) for semiconductor surface structures. Recent methodological advances in many-body physics will be discussed, including the modeling of self-energy, excitonic and local-field effects in large and complex systems. Potential applications to semiconductor surfaces functionalized with organic thin films will be discussed.

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