Oblique propagation in a cholesteric liquid crystal: 4 × 4 matrix perturbational solution

While deriving an exact closed-form solution for the general propagation problem in a cholesteric liquid crystal remains elusive, we present a perturbational treatment which is correct to the second order in the anisotropy parameter. The perturbation terms are given in closed form and can thus be easily used to study wave propagation phenomena in cholesteric liquid crystals under the conditions of oblique (i.e., not normal to the optic axis of the unidirectionally inhomogeneous media) incidence.