generalized ellipsometry

**Generalized Ellipsometry** is an **extension of standard ellipsometry that handles anisotropic, depolarizing, or non-specular samples** — going beyond the simple ($Psi, Delta$) framework to characterize materials where the optical response depends on polarization direction. **When Is Generalized Ellipsometry Needed?** - **Anisotropic Films**: Materials with different refractive indices along different crystal axes (birefringent). - **Tilted Optic Axes**: When the optical axis is not aligned with the sample normal. - **Gratings**: Periodic structures that mix polarization states (cross-polarization). - **Rough Surfaces**: Surfaces that depolarize the reflected light. **Why It Matters** - **Birefringent Materials**: Accurately characterizes crystalline films (HfO$_2$, TiO$_2$, sapphire) with anisotropic optical properties. - **OCD (Optical CD)**: Critical for scatterometry-based CD measurement of complex grating structures. - **Complete Model**: Captures effects that standard SE misses, preventing systematic modeling errors. **Generalized Ellipsometry** is **ellipsometry without simplifying assumptions** — handling anisotropy and depolarization that break the standard SE model.