Subject: How can light be circularly polarized

If the Magnetic Field and the Electric Field of an electromagnetic
wave are, by definition, existing at right angles to each other. How
can a radio or light wave have circular polarization in free space?

Birefringence explains the phenomenon while traveling through a 
medium,but does not explain to me how the polarization can continue
to rotate in space.

Does a photon of light that is circularly polarized have only specific
polarizations? e.g. 45 or -45 degrees?

Re: How can light be circularly polarized