Spatial solitons of Maxwell’s equations propagating in an isotropic Kerr material differ significantly from the classical soliton of the nonlinear Schrödinger equation unless the electric field is linearly polarized along a geometric axis of the soliton intensity pattern. In general the polarization state changes continuously as the beam propagates, with a period of millimeters for highly nonlinear materials. This effect is due to the form birefringence of the soliton-induced waveguide. Equivalently, a soliton of Maxwell’s equations is composed of both the TE and TM modes of the axially uniform waveguide it induces. Modal beating leads to the polarization dynamics.
© 1994 Optical Society of America
Allan W. Snyder, D. John Mitchell, and Yijiang Chen, "Spatial solitons of Maxwell’s equations," Opt. Lett. 19, 524-526 (1994)