Nonparaxial Gaussian beams: 1. vector fields

Rigorous analytical solutions were obtained for the vector field of a propa gating nonparaxial Gaussian beam in the vicinity of the beam focus. It is d emonstrated that a nonparaxial beam of the lowest order has six modes. Upon the limiting transition kz(0) much greater than 1, four of these modes exh ibit degeneracy and convert into a paraxial Gaussian beam, while the other two modes form the azimuth-symmetric TE and TM fields. A characteristic fea ture of the nonparaxial modal beam is the absence of symmetry between (stil l mutually orthogonal) electric and magnetic fields. The deviation from sym metry results in the appearance of negative energy fluxes in the vicinity o f the phase singularity manifested by Airy's fringes, "light drops" (specia l states of the light field), and "singularity islands". The obtained resul ts are in good agreement with other relevant data published. (C) 2000 MAIK "Nauka/Interperiodica".