Vortex Coronagraphy G. Serabyn Jet Propulsion Laboratory, California Institute of Technology A. Carlotti (IPAG), J. Hoffman (JH), D. Mawet (ESO), C. Norman (HST), L. Pueyo (HST), N. Kasdin (Princeton) ACWG2.5 Oct 24, 2013 Copyright 2013 California Institute of Technology. Government sponsorship acknowledged. The technical data contained in this document may be restricted for export under the International Traffic in Arms Regulations (ITAR) or the Export Administration Regulations (EAR)

The Vortex Coronagraph A vortex phase shifter applies a helical phase to focal plane Airy field Coronagraphic Image Input pupil Focal plane Pupil plane bypass vortex  = eim through vortex LCP mask PC mask Lyot stop Advantages: Phase mask  -Small IWA (chg. 2: 0.9 λ/D; chg. 4: 1.7 λ/D) (no central block) -High throughput -Clear 360 azimuthal FOV -Layout: simple: common w. Lyot, shaped pupil

Liquid Crystal Polymer (LCP) Vector Vortex Masks JDSU: Orientation defined by slit Beamco: Orientation defined by line focus Central defect ~ 1 micron   Charge 4 vortex: axis spins 2x as fast JDSU Second Gen. Covered central defect ~ 30 – 40 m

10% bandwidth test on JDSU gen 2 mask; 3-8 λ/D 10% BW avg. contrast for 3-8 λ/D = 1.1 x 10-8 (dominated by one bright dust speckle) 5.0 x 10-9 without bright speckle Used five 2% filters Wavefront control using all 10% BW

Vortex Mask Performance for 10% BW 9 x 10-9 average contrast over 1.5 to 9.5 λ/D dark hole for 10% BW dominated by a few dust particles or defects; new mask in hand Soon to test a 25% bandwidth mask

Broadband Performance Three approaches to broadband: Spectral Polarization Filtering: Multi-layer half-wave-plate vortex: LCP layers rotate (twist) as a function of depth Working with three companies: JDSU: New mask with 30 mu defect and cover is here Future: potentially, a classical broadband three-layer mask Beamco: Reduce central defect to insignificance; no central cover 25% BW twisted multi-layer mask with 3 micron defect is here Below 10-8 monochromatically with no cover North Carolina State: Lay down opaque spot first as reference; twisted multi-layer 20% BW; mid-range defect size; contract in place

Obscured Pupil Sources of Contrast Degradation On-axis secondary Secondary support legs Other small nubs Does the vortex coronagraph have solutions for all of these? Yes, in general; Vortices on Palomar, Subaru, VLT, LBTI So, what’s the problem? Promising solutions for the highly obscured input pupil recently proposed; basic codes now exist (written by Europeans) And B from Palomar: contrast ~ few 10-5 HD141569: Wahl et al., in prep.

Aperture Blockage: Two part solution: Several solutions for a secondary obstruction: Dual-stage vortex: (d/D)^4 rejection for charge 2 Three stage vortex: perfect rejection, but lots of optics Apodized vortex (Mawet et al. 2013): perfect rejection with few optics Solution for the spider support legs: ACAD: Active Correction of Aperture Discontinuities (Pueyo and Norman 2013)

The Ring Apodized Vortex require 0 in outer ring Input Pupil 2nd Lyot Pupil Mawet et al. 2013

RAVC charge 4: Add a ring Theoretical throughput for transmissive apodizer Transmission low for high charge and large obscurations

Current AFTA Vortex Layout Provides a Pupil Usable for an Apodizer similar to band-limited & shaped pupil (at least) apodizer vortex

ACAD for Vortex Coronagraphs ACAD + RRAVC (Pueyo, Mawet, et al.): ~510-9 @ 2.0λ/d, 33% BW ~70% throughput (l=2), ~50% (l=4) (or a PIAA-like solution for spider) Pueyo et al. 2012, 2013

Solution Options Options Throughput SP-AVC + ACAD high RAVC + ACAD med low Key: SP-AVC: uses shaped pupil apodizer RAVC: uses uniform apodizer Two types of apodizer: “uniform ring” or “shaped pupil”

Submitted Vortex Solution: ACAD Hoffman, Norman, Pueyo Stroke ~ 1 micron along supports; max ~ 1.5 microns in small region

Optimized “shaped pupil’’ apodizer for AFTA “Camouflaging the support legs Increased throughput by relaxing strict zero-flux condition Light can be present at high spatial frequencies Mask throughput 47% apodizer Lyot stop A. Carlotti et al. 2013, SPIE 8864-34, 8864-60

Predicted Contrast for Submission IWA ~ 3λ/D Can see closer in

Transmission and Search Space Maximum system transmission ~ 11% IWA ~ 3.0 λ/D OWA ~ 19 λ/D IWA OWA

Yield of RVs

Conclusions and Disclaimer New software hurriedly written and debugged to evaluate the vortex option for the recently-cleared AFTA pupil Lots being learned in a hurry Final parameter errors found and fixed A vortex solution with a system transmission of 11%, and IWA ~ 3 λ/D has been identified