High contrast internal and external coronagraph masks produced by various techniques Kunjithapatham Balasubramanian*, Daniel Wilson, Victor White, Richard Muller, Matthew Dickie, Karl Yee, Ronald Ruiz, Stuart Shaklan, Eric Cady, Brian Kern, Ruslan Belikov 1 , and Olivier Guyon 2 , N. Jeremy Kasdin 3 Jet Propulsion Laboratory, California Institute of Technology 4800 Oak Grove drive, Pasadena, CA 91109 1 NASA Ames Research Center, Moffett Field, CA 2 University of Arizona, Tucson, AZ; 3 Princeton University, NJ kbala@jpl.nasa.gov Tel: 818-393-0258 ABSTRACT Masks for high contrast internal and external coronagraphic imaging require a variety of masks depending on different architectures to suppress star light. Various fabrication technologies are required to address a wide range of needs including gradient amplitude transmission, tunable phase profiles, ultra-low reflectivity, precise small scale features, and low-chromaticity. We present the approaches employed at JPL to produce pupil plane and image plane coronagraph masks, and lab-scale external occulter type masks by various techniques including electron beam, ion beam, deep reactive ion etching, and black silicon technologies with illustrative examples of each. Further development is in progress to produce circular masks of various kinds for obscured aperture telescopes. Keywords: Exoplanet, coronagraph, mask, occulter, PIAA, Shaped pupil 1. INTRODUCTION Detection and characterization of faint exoplanets require an efficient coronagraph to suppress the star light and allow planet light to get through to the final image plane of the telescope. Various coronagraph architectures are being studied for this purpose. Central to all coronagraphs are star light suppressing masks to function either in the focal plane or pupil plane or both. Modified Band Limited Coronagraph (BLC, Trauger 1,2 ), Shaped Pupil Coronagraph (SPC, Belikov 3 ), Vector Vortex Coronagraph (VVC, Mawet 4 ), and Phase Induced Amplitude Apodization Complex Mask Coronagraph (PIAACMC, Guyon 5,21 ) are chief among these architectures. Different kinds of masks are needed for each of these architectures and hence different technologies are needed to produce them. In addition, with the availability of the 2.4 m Astrophysics Focused Telescope Assets (AFTA) to NASA, the need has arisen for advanced coronagraphs that function with an obscured aperture. This further stresses the importance of high-quality circularly symmetric masks with accurate amplitude and phase profiles to perform apodization and achromatization at high levels of contrast for exoplanet detection. We present here illustrative examples of masks produced by various techniques at JPL. 2. BACKGROUND AND CURRENT EXPERIENCE Two major categories of masks are needed for different types of coronagraph architectures: (1) achromatic focal plane mask, and (2) reflective or transmissive binary apodizers and pupil plane masks. To fabricate such masks, different complementary techniques have been explored at JPL for development and advancement: (1) electron beam evaporation through a scanning slit, (2) electron beam lithography, (3) deep reactive ion etching, (4) focused ion beam deposition, and (5) cryogenic black silicon processing. *kbala@jpl.nasa.gov; phone: 818-393-0258