Finite–element analysis of plane wave diffraction from dielectric gratings

An analysis method based on the finite element method is proposed for solving the problem of diffraction of a plane wave by a dielectric grating. For both the TE and TM wave incidences, a systematic formulation is presented. Although numerous analysis methods have been reported on dielectric gratings, it is necessary in general to divide a grating into several layered planar dielectric gratings when a dielectric grating with an arbitrary profile is analyzed. On the other hand, the finite element method used in this paper enables direct treatment of a dielectric grating with an arbitrary profile without multilayered division. In practice, gratings made of grooves with rectangular, sinusoidal and trapezoidal profiles created on the surface of a semi-infinite dielectric medium are analyzed. The results of analysis on the diffraction characteristics are presented. Next, as an example for groove gratings with complex geometry, the analysis results of the diffraction efficiency are presented for a holographic grating fabricated at IBM. The analysis results agree well with those by other methods and with experimental values so that the validity and usefulness of the present method are confirmed.