Design, fabrication and characterization of phase masks for astronomical applications

In this work, a three-dimensional fabrication process was used to create a phase modulating device for astronomical applications. This phase mask, also known as spiral phase plate (SPP), finds its application in astronomy for optical vortex coronagraphy in the search of extra solar planets. SPPs are helicoidal transmission optical devices, similar to spiral staircases, that imprint vorticity onto the phase distribution of the incident light beam, changing it smoothly and continuously, while preserving the direction of the optical axis. In this paper we present a fabrication process based on electron beam lithography (EBL) and optical and topographical characterization of a nanofabricated SPP.