What experiment proves light is a transverse electromagnetic wave consisting of both electric and magnetic fields? Can we somehow produce visible light by some kind of antenna or other mechanism that would produce light in the form of a transverse EM wave?
Atoms transitioning between a higher energy state and a lower one are basically little antennas that can produce visible light. Their electronic charge density is moving back and forth, creating an oscillating electric dipole moment that is conceptually identical to that of, say, a radio antenna but on a smaller and faster scale.
Of course, there is also the general argument that modeling light as transverse EM radiation is consistent with innumerable observations. For example, this theory predicts that light should exert a particular pressure, and it does. We see this when using solar sails.