Metrological atomic force microscopy integrated with a modified two-point diffraction interferometer

Abstract

We propose a new concept for a metrological atomic force microscope integrated with a modified two-point diffraction interferometer that can determine the xyz-coordinates in an absolute manner. The interferometer consists of two single-mode optical fibers; one fiber is fixed to be stationary and the other is attached on an xyz-stage that moves with the measuring sample. The two fibers generate two separate spherical wavefronts that interfere with each other. Phase information can be obtained from this interference fringe pattern by applying well-known phase shifting techniques. This phase information is very sensitive to the relative coordinates between the two fiber ends, and thus the xyz-coordinates of the stage can be measured with respect to the fixed machine structure. A 100 mu m x 100 mu m x 20 mu m working volume is available in the proposed system.