Roughness measurement with nanoscale resolution by symmetric array of optical vortices

Abstract

In present report we review the principles and applications of interference vortex method for the real time determination of polished optical surface roughness for transparent and reflecting materials with using of symmetric Laguerre-Gaussian array as a probe beams and reference beams with low topological charge. High spatial resolution caused by interference of vortices and their phase sensitivity, which is automatically analyzable to retrieve the 2D and 3D shape of micro- and nanostructured surfaces is applicable for non-destructive roughness testing of thin films and solid microstructures. The longitudinal and transverse resolution down to 1.75 nm and 7 nm respectively for visible light sources is achieved by the proposed method. The dependence of the rotational angle of the resulting interference pattern in form of two-petal laser beams on the optical path difference and sample thickness for two singular beams superposition is considered in detail.