Physically meaningful solutions of Maxwell equations on S3 × R spacetime are derived, as linear superposition of the α- and β-polarized, left- and right-moving modes, of positive and negative frequencies. Using the orthonormal electric and magnetic fields intensities, we compute the components of the Umov-Poynting vector, of the effective momentum and the energy density. In the last section, non-trivial solutions for the 4-potential A, satisfying the F= 0 property, are employed to analyze how the presence of the electromagnetic vacuum modes is affecting the solution of the Klein-Gordon equation, in comparison to its usual form on the Minkowskian background.