LIGHT-DIFFRACTION FROM ROUGH GRATINGS

Two holographic diffraction gratings with very similar parameters, des igned for maximum performance in TM polarization, are investigated, th eir diffraction efficiency measured, an electron microscopic picture o f their surface observed, and numerical simulation of light diffractio n done with the surface roughness taken into account. It is demonstrat ed numerically that a small-scale roughness imposed on the grating sur face could increase significantly both scattering and absorption from the surface, this influence being greater in the TM case. A very good coincidence between the numerical and experimental data is obtained in TE polarization, whereas in TM polarization only a qualitative agreem ent exists.