“…with I 2 denoting the 2 × 2 identity matrix. It has been shown that under mild assumptions on v(x), n(x, k) and Σ(x, k) equation ( 15) is well-posed and that the solution W(x, k, t) is Hermitian [9]. Furthermore, the solution is related to the four Stokes parameters I, Q, U, V, see [5,7], as…”