Fabrication and characteristics of free-standing shaped pupil masks for TPF-coronagraph

Abstract

Direct imaging and characterization of exo-solar terrestrial planets require coronagraphic instruments capable of suppressing star light to 10 -10 . Pupil shaping masks have been proposed and designed 1 at Princeton University to accomplish such a goal. Based on Princeton designs, free standing (without a substrate) silicon masks have been fabricated with lithographic and deep etching techniques. In this paper, we discuss the fabrication of such masks and present their physical and optical characteristics in relevance to their performance over the visible to near IR bandwidth.

Demonstration of high contrast with an obscured aperture with the WFIRST-AFTA shaped pupil coronagraph

“…Shaped pupils in the past 9,10,12 have been transmissive, primarily using holes etched through wafers with deep reactive ion etching (DRIE) to create the pupil shape. 13 These masks were freestanding and self-supporting, and were successfully demonstrated at high contrast in the HCIT previously, including 4 × 10 −9 contrast in monochromatic, 790nm laser light with 2DMs in the summer of 2013. 15 Unfortunately, the features of the AFTA pupil-with a slightly-off-axis secondary, six spiders, and additional small circles around the secondary-proved hostile enough to optimization that pupil shapes could not be found without small isolated regions that could not be built in a freestanding optic, and new technology was required.…”

A high dynamic-range instrument for SPICA for coronagraphic observation of exoplanets and monitoring of transiting exoplanets

“…Binary-shaped pupil-mask coronagraphs are in principle achromatic (except for the PSF scaling with wavelength) and robust against telescope pointing. [37][38][39][40][41][42][43][44][45][46][47][48][49] In this coronagraph, a single binary pupil mask modifies the PSF and provides the required contrast. Some binary shaped pupil masks were designed for the SPICA pupil with the obscuration as illustrated in Figure 5.…”

“…[ [37][38][39][40][41][42][43][44][45][46][47][48][49] In this coronagraph, a single binary pupil mask modifies the PSF and provides the required contrast. Some binary shaped pupil masks were designed for the SPICA pupil with the obscuration as illustrated in Figure 5.…”

Shaped pupil coronagraphy

“…There are small differences in the specifics of the process between NIST and JPL, such as the wafer used, durations of etches, etc., but the overall procedure is very similar. More details can be found in Balasubramanian et al [9]. In addition to this process, JPL has developed a new process using silicon-onoxide (SOI) wafers.…”