The light whose endpoints of the rotating electric vector trace a circular trajectory is called circularly polarized light, which is a special case of elliptically polarized light. When the propagation directions are the same, the vibration directions are perpendicular to each other and the phase difference is constant as φ=(2m±1/2)π, the circularly polarized light with regular changes in electric vector can be synthesized after superposition of two plane polarized lights.
