While diffractive optical elements can be modeled in both sequential and non-sequential mode in ZEMAX, non-sequential mode's ray splitting capabilities can be quite advantageous for diffractive modeling.

Open the file "Samples > Non-sequential > Diffractives > Diffraction grating multiple orders.zmx".

Notice that the single input ray is split into five rays at object 2.

   

In this case, the rays are not splitting as a result of a coating or scattering settings. Instead, we are seeing the splitting of energy into multiple diffractive orders by the transmission diffraction grating (object 2). The fundamental property of this grating (i.e. the grating frequency in lines per micron) is defined in the parameter columns for this object. Notice that the Diffraction Grating object has the same parameters as a Standard Lens object plus a diffraction grating frequency parameter (lines per micron).

The ray splitting settings for this object are set in the Diffraction tab of the Object Properties dialog.



In this tab, the relative amount of energy that is split into each order is specified.

TIP:  Users of the full, licensed version of ZEMAX can use custom diffractive DLLs in which arbitrary order splitting can be specified. These DLLs can also be used to explicitly specify all of the properties of rays after diffraction including relative energy, direction cosines and electric field orientation and magnitude.