Black lines are axes (both spatial axes, at a snapshot in time), and blue lines represent the surfaces of constant phase of a plane wave traveling along the horizontal axis.
However, obviously most light beams are not infinite in extent. This means that most light beams are composed of components with nonzero transverse spatial frequency.
My question is, what do those components look like?
If I put such a plane wave through a lens, it gets focused to a different spot in the lens's Fourier plane, leading me to believe that this is the right idea.
Are there other ways to make a plane wave with nonzero spatial frequency aside from just "tilting" the beam?
EDITS: To clarify what I meant by "spatial frequency" as well as the axes on my drawings, and to hone in on my exact question.