Diffraction of surface electromagnetic waves by the open end of a strip optical microwaveguide

A theoretical study is made of the diffraction of surface electromagnetic waves by the open end of a strip optical microwaveguide. An approximation equivalent to the Kirchhoff approach is used to obtain analytic dependences for the angular distribution of diffracted waves in the far-field zone in the Fraunhofer diffraction case and a study is made of the distribution of electric fields of the diffracted waves in the near-field zone in the Fresnel diffraction case. It is shown that the angular distribution of the diffracted waves depends on the mode index of a strip microwaveguide and it differs considerably for thin-film and graded-index strip microwaveguides in a plane perpendicular to the waveguide. It is shown that in solving of the problem of the end contact between strip microwaveguides and fiber waveguides it is possible to ignore the distortion of the distribution of the electric field of the fundamental mode at the open end of a strip microwaveguide.