Design of diffractive optical micro-relief for waveguided beam focusing

Abstract

Introduction of diffractive optical elements (DOEs) opened the possibility to control field distribution in the cross-section of laser beam. In fact, by use of DOE one can focus the laser beam into predicted areas as well as form the beam with pre-given behavior propagation through waveguide medium. The diffractive micro- relief can be realized either on the separated substrate or directly on the waveguide surface. Some applications need the focusing of the output waveguided beam into predicted area. But generally, one can use diffractive micro-relief on the output of waveguide in the case of excitement of selected waveguide mode only. Another applications need selected waveguide mode excitement for fiber sensor sensitivity improvement. In the present talk it is suggested to use micro-relief on the input waveguide cross-section for selected mode excitement. The strategy of the search of waveguide mode with intensity distribution closed to the illuminating beam intensity distribution is suggested to be used. Corresponding numerical procedure is described. Computer simulation results are presented.