Local optical field variation in the neighborhood of a semiconductor micrograting

TL;DR

This study investigates the local optical field variations near a semiconductor micrograting using optical scanning, revealing effects of light penetration depth and diffraction image displacement.

Contribution

It introduces a method to measure local optical fields around microgratings and models the effects of light penetration and diffraction displacement.

Findings

High contrast imaging of micrograting achieved

Edge resolution limited by light penetration depth

Diffraction image displacement increases with distance from surface

Abstract

The local optical field of a semiconductor micrograting (GaAs, 10x10 micro m) is recorded in the middle field region using an optical scanning probe in collection mode at constant height. The recorded image shows the micro-grating with high contrast and a displaced diffraction image. The finite penetration depth of the light leads to a reduced edge resolution in the direction to the illuminating beam direction while the edge contrast in perpendicular direction remains high (~100nm). 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.