For a sinusoidal plane wave propagating along z axis the orbital angular momentum density vanishes. The spin angular momentum density is in the z direction and is given by L = | E | 2 8 π π ω ω ( | ⟨ ⟨ R | ψ ψ ⟩ ⟩ | 2 − − | ⟨ ⟨ L | ψ ψ ⟩ ⟩ | 2 ) = 1 ω ω E c ( | ψ ψ R | 2 − − | ψ ψ L | 2 ) where again the density is averaged over a wavelength.