Rotating scale-invariant electromagnetic fields

The concept of scalar fields with uniformly rotating intensity distributions and propagation-invariant radial scales is extended to the case of electromagnetic fields with rotating but otherwise propagation-invariant states of polarization. It is shown that the conditions for field rotation are different for scalar and electromagnetic fields and that the electromagentic analysis brings in new aspects such as the possibility that different components of a rotating electromagnetic field can rotate in opposite directions. (C) 2001 Optical Society of America.