In CW excitation, the time dependence of the incident field is a single frequency
sinusoidal function. For example the incident Ey field has the following form:

FDTD - Equation 52

where A is the field amplitude, AF(x, zinc) is the transverse field distribution at the
incident plane location zinc.

The initial phase offset θis the phase difference between points in the incidence
plane. This offset can be adjusted to define the direction of the incident field.
ω = (2π ⁄ λ)c  is the frequency of the input wave. In the CW case the optical wave
analog propagates until it reaches the stationary state everywhere in the
computational window.