How to generate a plane wave that is constant in time

[hfdihfd]

I understand that this generates a time-harmonic plane wave whose time dependence is $e^i\omega t$.

sources = [mp.Source(mp.ContinuousSource(frequency=frequency, is_integrated=True),
        component = mp.Ex,
        center=sourceLocation,
        size=sourceSize
        )]

Such a plane wave oscillates in time. I wonder if it is possible to generate a plane wave that is constant in time. That is, it can be expressed as a beam of light like the following: