Single-shot digital holography of multiple-beam Fizeau holograms for optical phase reconstruction through the focal depth of optical fibers

Abstract

Multiple-beam Fizeau interference (MBFI) is characterized by its ability to represent the fine features of phase objects. Single-shot digital holographic interferometry (SSDHI) is used for numerical focusing of the recorded holograms. In this work, the two methods are gathered and employed for solving the problem of studying the thick phase objects. The problem of thick phase objects, such as optical fibers, in MBFI is the full focusing of the fiber's optical phase in one-time single shot phase map. The proposed method is designed to collect the optical phase map due to the optical fiber through the focal depth. The main idea is based on the analysis of the MBFI to several two-beam interference sets. Each two-beam interference is treated by SSDHI method to get the optical phase at different planes of focus inside the object. Then, the resultant optical phase due to the optical fiber is collected from these planes of focus. Retrieving the optical phase maps of the multiple-beam holograms through the focal depth, for the first time, is possible using the angular spectrum method. In this case, a laser source with quite long coherence length is used as a light source.The proposed method is applied on two thick samples of, single mode and graded index, optical fibers to reconstruct the resultant optical phase maps through the focal depth. The reconstructed optical phase maps are determined for the harmonics of MBFI holograms’ angular spectra. The method proves its ability to provide more accurate, numerical focusing and phase maps reconstruction. Where, MBFI analyses indicate the magnification of optical phase differences.