RSM
Radiation Spectrum Method : a modal BPM (Beam Propagation Method)
RSM (Radiation Spectrum Method) is a 2D rigorous tool to solve the Maxwell equations for the propagation of light in integrated optics or photonics devices. It makes use of an eigenmode expansion method to solve the electromagnetic problem. This software running on Windows and MacOS comes with a GUI that permits to define with the aid of files or scripts the arbitrary and complex geometry of the waveguide. Of that way any waveguide geometry can be handled. Several plots are available : refractive index plot, field propagation plot and modes spectrum plot. This permits, with the interpretation of the guided and radiation modes spectrum, a physical understanding of the propagation mechanisms in the integrated optical device under evaluation. The complex geometry of the component is discretized in a stack of multilayer dielectric waveguides.
See : https://ipp.icube.unistra.fr/index.php/Photonics_Modeling_and_Simulation:RSM