Limits of vortex fiber nulling

Abstract

Stars are known to be partially coherent light sources and this might affect the efficiency of the nulling interferometry methods. In this paper, we investigate the limits of vortex fiber nulling (VFN) measurements by calculating the spatial coherence of stars with exoplanets detected using direct imaging. We found that most stars with directly imaged exoplanets have spatial modes other than l = 0. While the weights of these spatial modes may appear small compared to potential planetary signals that will enter the fiber, such signals could still interfere with the planetary signal and alter planetary properties obtained using direct imaging.