Distortion and cross polarization of a simple gaussian beam on diffraction from grating couplers for Q.O. gyrotrons

We examine the distortion and cross polarization of a Gaussian beam diffracted from a planar grating with curvilinear grooves or from an elliptical grating with curved grooves placed in the Littrow mount. The electromagnetic field diffracted from the gratings in the 0th order and propagating to an HW11 waveguide has been numerically computed. The output patterns, distortion, and cross polarization have been obtained for the gratings; the results agree well with the cold results. The comparison between the gratings shows that the elliptical grating is more effective than the planar grating. (author) 2 figs., 1 tab., 5 refs