- #1
- 3
- 0
I understand how polarization can be explained using EM waves. However, I am unable to understand how to explain how polarization filters work when we use the concept of photon spins. Can someone help me with that?
This is because the little group of a massive particle, SU(2), is different than the little group of a photon, E(2).Does that mean, instead of saying that the photon has spin 1, we should instead say that it has helicity 1? I didn't realize that the representations of the Poincare group for massless particles cannot be labeled by spin!
The usual terminology is to say that the photon has spin 1 (in the sense of ##\vec{J}^2## has the lowest eigenvalue ##1 \cdot (1+1)=2##). Since the photon is massless this implies that there are two spin-degrees in freedom. A natural choice for a single-photon basis is to take momentum eigenvectors and eigenvectors of the angular momentum component in direction of the photon's mopmentum, i.e., the helicity, and this helicity ##h \in \{-1,1\}##.Does that mean, instead of saying that the photon has spin 1, we should instead say that it has helicity 1? I didn't realize that the representations of the Poincare group for massless particles cannot be labeled by spin!