The Grating and Cross Grating boundary conditions, together with the Diffraction Order (Grating) and Diffraction Order (Cross Grating) subnodes, respectively, are used to model the separation of rays by diffraction at a periodic microstructure. Typically, the unit cell of the microstructure is comparable to the wavelength. The Grating is periodic in one direction and homogeneous in the orthogonal direction, whereas the Cross Grating is periodic in two directions. Either boundary condition can reflect or transmit rays and emit secondary rays. You can specify the direction of periodicity and the size of the unit cell.

The Mirror boundary condition is a simplified Wall that only causes specular reflection.

The Axial Symmetry boundary condition is only available in 2D axisymmetric models. It is automatically applied at the axis of symmetry and can’t be applied anywhere else.

Optical devices like the Linear Polarizer and Linear Wave Retarder are available when ray intensity or power is computed. They don’t have any effect on the ray direction but they can affect the ray polarization.