Phase-induced amplitude apodization complex-mask coronagraph tolerancing and analysis

Abstract

Phase-Induced Amplitude Apodization Complex Mask Coronagraphs (PIAACMC) offer high-contrast performance at a small inner-working angle (< 1 lambda/D) with high planet throughput (> 70%). The complex mask is a multi-zone, phase-shifting mask comprised of tiled hexagons which vary in depth. Complex masks can be difficult to fabricate as there are many micron-scale hexagonal zones (> 500 on average) with continuous depths ranging over a few microns. Ensuring the broadband PIAACMC design performance carries through to fabricated devices requires that these complex masks are manufactured to within well-defined tolerances. We report on a simulated tolerance analysis of a "toy" PIAACMC design which characterizes the effect of common microfabrication errors on on-axis contrast performance using a simple Monte Carlo method. Moreover, the tolerance analysis provides crucial information for choosing a fabrication process which yields working devices while potentially reducing process complexity. The common fabrication errors investigated are zone depth discretization, zone depth errors, and edge artifacts between zones.