Local optical field variation in the neighborhood of a semiconductor micrograting

The local optical field of a semiconductor micrograting (GaAs, 10 X 10,mu m) is recorded in the middle field region using an optical scanning probe in collection mode at a constant height. The recorded image shows the micrograting with high contrast and a displaced diffraction image. The finite penetration depth of the light leads to a reduced edge resolution in the direction of the illuminating beam while the edge contrast in the perpendicular direction remains high (similar to 100 nm). We use the discrete dipole model to calculate the local optical field to show how the displacement of the diffraction image increases with increasing distance from the surface. (c) 2006 Optical Society of America.