Abstract
This work investigates the link between surface topography at the mesoscopic scale and emissivity at the macroscopic scale within the Morphology-Driven Radiative Analysis and Design framework. The analysis is conducted on periodic lamellar titanium gratings characterized by the period P, groove width W, and groove depth H. Their emissivity is investigated by comparing three modelling approaches: the Agababov model, ray-tracing simulations, and Rigorous Coupled-Wave Analysis (RCWA), used as the electromagnetic reference. A numerical design comprising 8,100 configurations is used to investigate the effects of geometry, wavelength, and incidence angle. The results show that the accuracy of the geometrical-optics models (Agababov and ray tracing) is governed by the relative scales of the surface geometry and wavelength, as well as by the incidence angle. The largest discrepancies with respect to the electromagnetic solution occur at small P/λ, particularly when associated with large H/λ. The resulting validity regions and their dependence on incidence angle are consistent with the trends reported by Tang and Fu. Overall, ray tracing does not systematically outperform the Agababov model, which exhibits errors of the same order over substantial regions of the investigated parameter space, highlighting its ability to provide reliable predictions despite its simpler formulation.