[[File:PMOM111.png]]
where ?η<sub>0</sub> = 120p 120π is the characteristic impedance of the free space, '''k<sub>1</sub>''' and '''k<sub>2</sub>''' are the unit propagation vectors of the incident plane wave and the wave reflected off the topmost substrate layer, respectively, and '''ê<sub>1</sub>''' and '''ê<sub>2</sub>''' are the polarization vectors corresponding to the electric field of those waves. R is the reflection coefficient at the interface between the top half-space and the topmost substrate layer and has different values for the TM and TE polarizations.
EM.Cube's [[Planar Module]] provides the following polarization options:
* RCPz
The direction of incidence is defined through the theta and phi angles of the propagation vector in the spherical coordinate system. The default values are ? θ = 180° and f φ = 0°, representing a normally incident plane wave propagating along the -Z direction with a +X-polarized electric field vector. In the TM<sub>z</sub> and TE<sub>z</sub> polarization cases, the magnetic and electric fields are parallel to the XY plane, respectively. The left-hand (LCP) and right-hand (RCP) circular polarization cases are restricted to normal incidences only (? θ = 180°).
To define a plane wave source, follow these steps: