The rotation of a photon around an axis with orientation given by the vector n⃗ is the action representated by the operator $ U = e^{ i \theta \vec{n}. \vec{J} } $. But to get a clearer understanding of what that would mean in a specific case... $$ $$ Suppose $ \vec{n} $ were parallel to $ \vec{J} $ and that and the photon's direction of propagation is along z$z$ and that at time $t = t_0$, the photon's electric field $ \vec{E} $ were pointing up along y$y$ direction. $$ $$ Suppose now at $t_0$, the photon is 'rotated' about $ \vec{n} $ by an angle $ \Pi $, (180 degrees) what now are the directions of $ \vec{E} $ and $ \vec{J} $ ?