Ay. Savchencko et By. Zeldovich, WAVE-PROPAGATION IN A GUIDING STRUCTURE - BEYOND THE PARAXIAL APPROXIMATION ONE-STEP, Journal of the Optical Society of America. B, Optical physics, 13(2), 1996, pp. 273-281
Propagation of electromagnetic waves is considered for a medium with (
x, y)-dependent locally isotropic dielectric and magnetic susceptibili
ties epsilon(ik) = epsilon(x, y)delta(ik) and mu(ik) = mu(x, y)delta(i
k), i.e., for a waveguide. In the paraxial approximation the polarizat
ion is disconnected from the propagation. We have developed a self-con
sistent theory of the postparaxial corrections. It allows, in particul
ar, for the description of intrafiber geometrical rotation of polariza
tion and its inverse phenomenon, the optical Magnus effect, which are
both determined by the profile of refractive index n = root epsilon mu
only and constitute spin-orbit interaction of a photon. The birefring
ence splitting of linearly polarized modes or meridional rays on the o
ther hand, turns out to be dependent on the gradients of impedance rho
= root mu/epsilon the quadrupole part of spin-orbit interaction. An i
mportant point of the theory is a transformation of field variables su
ch that the z-propagation operator becomes Hermitian, in analogy with
the transitions from a full relativistic Dirac equation to the Schrodi
nger-Pauli equation with spin-orbital corrections. A theoretical expla
nation is given for the phenomenon previously observed in experiment:
preservation of circular polarization by an axially symmetric step-pro
file multimode fiber and depolarization of an input linearly polarized
wave by the same fiber. (C) 1996 Optical Society of America