Phase masks in astronomy: From the Mach-Zehnder interferometer to coronagraphs

Phase masks have numerous applications in astronomical optics, in particular related to two themes: coronagraphy for detection and analysis of extrasolar planets or circumstellar disks, and wavefront analysis for extremely precise adaptive optics systems or cophasing of segmented mirrors. I review some of the literature concerning phase masks and attempt to bridge the gap between two instrumental systems in which they are often found: the Mach-Zehnder interferometer and the coronagraph.