Angular distribution of light scattered from a sinusoidal grating

The angular distributions of light scattered by gold-coated and aluminum-coated gratings with amplitudes of similar to 90 nm and periods of 6.67 mu m were measured and calculated for light incident from a He-Ne laser at an angle of 6 degrees. Experimental results are compared with predictions of Beckmann's scalar theory and Rayleigh's vector theory. The measured scattering pattern has a background of scattered light due mainly to residual surface roughness. Also the power in the higher-order peaks is larger by several orders of magnitude than the computed one, which can be attributed mainly to the low-order contributions of the harmonics in the profile. (C) 2000 Optical Society of America OCIS codes: 050.1950, 050.2770, 050.1960.