SKM 2023 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 6: Poster

KFM 6.3: Poster

Dienstag, 28. März 2023, 17:00–19:00, P3

Modelling of CARS — •Leonard M. Verhoff and Simone Sanna — Instutute for theoretical physics, Giessen, Germany

Coherent anti-stokes Raman spectroscopy (CARS) is a widely used method for material characterization which has been recently extended to crystalline solids. Even though it relies on the same vibrational modes as Raman spectroscopy, it yields a much stronger output signal. Being a third order, non-linear optical process, it depends on the material’s χ⁽³⁾ tensor.

In this contribution, we report on our theoretical modelling of the CARS-signal. In particular, we model the generation of the signal beam by solving the underlying differential equations resulting from Maxwell’s equations numerically for LiNbO₃, to extract a frequency-dependent amplitude that is also measured in experiments. The χ⁽³⁾ tensor is calculated from first principles using density functional theory before. Exploiting the symmetry of LiNbO₃ crystals, lower order non-linear optical effects can be neglected.

The partial differential equations defining the signal beam are further simplified by assuming plane waves for all involved lasers, including the pump, stokes and probe beam and explicitly using a specific scattering geometry.