Gaussian beam reflection from Fizeau interferential wedge

摘要

The goal of the present paper is to develop a procedure for calculation of the fringe pattern in reflection for Fizeau interferntial wedge considering both positive and negative incidence at which the incident light beam undergoes multiple reflections within the wedge in direction of increasing or decreasing wedge thickness respectively. High-reflectivity coatings wedges with apex angle of 5 - 100 μrad and thickness of 5 - 500 μm are considered. To avoid the drawbacks of the plane-wave approximation and to calculate the interference pattern for a limited beam illumination at any distance from the wedge, we proposed a plane-wave expansion approach. We analyzed the wedge interaction with a Gaussian beam as a beam structure of particular importance in laser technique. In addition, an analytical solution of the involved integrals was obtained for the Gaussian intensity distribution. It was shown that both contra-incidences of the light beam could be described by the same mathematical expressions, i.e. the reflected fringe pattern at positive incidence could be considered as prolongation of the reflected pattern at negative incidence at some distance from the wedge. Experimental verification is also provided.