Elements are construction blocks of any schema in rezonator.
The element can describe a general optical component such as a mirror or crystal. Additionally, it can express some physical but non-material entity - a distance between optical components, for example. Finally, it can also serve as some virtual helper object - point, for example.
rezonator supports a set of standard elements organized in a catalog.
The application utilizes conventional ABCD-matrix approach (by Kogelnik and Li) to compute the propagation of paraxial Gaussian beams through an element. In calculations, each element represented by its ray matrix.
You don’t have to assign matrices for elements manually. Instead, you can provide values for some typical element parameters - a focal length of a lens, thickness and refractive index for a crystal, and others. The software automatically computes element matrices based on these parameter values.