Hitting the diffraction limit
with the VORTEX project
Olivier Absil
FNRS Research Associate University of Liège
The birth of a concept
• FQPM à sub-‐wavelength gra@ngs à Annular Groove PM
•
Advantages of the AGPM
• Inner working angle ≈ 1 λ/D
• Clear 360° discovery space
• Achroma@c (SG design)
• Easy to implement 2
0 0
π π
Mawet, Riaud, Absil & Surdej 2005
Grating design/optimization
3
Delacroix et al. 2013
Lo g(n ull de pth ) -‐4 -‐3 -‐2 3.5 3.6 3.7 3.8 3.9 4.0 4.1 Log(peak rejec@on)
Etching on CVD diamond
•
Nanoimprint lithography + dry plasma etching
• N band (gra@ng period = 4.6 µm)
• L band (gra@ng period = 1.4 µm)
•
Parameters close to op@mal … need to test!
4N band (Nov 2009) N band (Feb 2012) L band (Sep 2012)
1.4 µm
Forsberg & Karlsson 2013
4.7 µm 4.6 µm
Setting up the bench
5 “Yacadire” @ Paris-‐Meudon
Anguish…
High performance
7 1 10 100 1000 Pe ak re je c7 onDelacroix et al. 2013
Bliss!
Installation at VLT
9
NACO: science demonstration
Raw image of β Pic Post-‐processed image
10
Absil et al. 2013
Sensitivity to inner planets
11
Absil et al. 2013
β Pic b
New discovery
The VORTEX project
(2013-‐2018)12
WP1
Exploita@on
Improvement
WP2
WP3
Performance
Observa@onsOp@mal image processing Other telescopes
Improved mid-‐IR AGPMs Extension to K and H bands
Higher topological charges
Perfo simula@on & tes@ng Post-‐coronagraphic WF sensing
Vortex quantum proper@es
Highest gain
WP1: ScientiWic exploitation
• L-‐band = sweet spot for
exoplanet imaging
• Complementary to XAO
near-‐IR imagers à characteriza@on
• Access to new
parameter space à
targeted surveys
• New perspec@ves on
more telescopes (Keck
coming soon) 13
L
WP1: image processing
WP2: manufacturing
• Bewer control of gra@ng
parameters
• Solvent-‐assisted micro-‐ moulding replaces NIL
• All etching recipes further op@mised
• Steeper side walls
• New L-‐band AGPMs
etched, currently tested
• Improvement of AR
performance
• Etching tests for K-‐band
AGPMs to start soon 15 1
Solvent-assisted micro moulding
4
R1813:AZ EBR 6000 rpm 30 s
Cut-out stampC
115°C 60s
Solvent-assisted micro moulding
5
WP2: charge-‐2 vortex (AGPM)
•
Op@mized L+M band
AGPMs under study
• Goal: 10-‐3 over whole
L+M band
•
Designs for shorter
wavelengths (H-‐K) to
be op@mised axer
feedback from
etching
16
! VVC! Lb![nm]! Etch!depth!
[µm]! Etch!time!(4!cycles)! Date! Defect! B1_D4! 570B580! 4.72B4.86! 09!min!45!s! 2014B03B06! ! B1_D5! 580B590! 4.72B4.86! 09!min!45!s! 2014B03B06! ! B2_D3! 590B600! 4.81B4.95! 10!min!10!s! 2014B04B02! Rough! B2_D4! 570B580! 4.81B4.95! 10!min!10!s! 2014B04B02! ! B3_D1! 580$590& 4.71B4.80! 09!min!40!s! 2014B04B14! ! B3_D3! 570$580& 4.75B4.84! 09!min!45!s! 2014B04B14! Scratch! ! ! ! Possible!! B2_D3& B2_D4& & & B1 _D 4 & B1 _D 5 & & & B3 _D 3& & B3 _D 1&
WP2: charge-‐4 vortex
•
Rejec@on in θ
4•
Mandatory for near-‐
infrared applica@ons
on ELTs
17Step'2:'FDTD'
!'Phase'ramp
' 8! transmission λ/D charge-‐2 charge-‐4 0 1 2 1WP2: charge-‐4 vortex
22! 18 17!Phase'ramp:'SGVC4'with'lines
' 51.2'x'51.2'µm' dx'='dy'='0.1'µm' dz'='0.2'µm' 204.8'x'204.8'µm' dx'='dy'='0.2'µm' dz'='0.2'µm' ' 0 1 2 3 4 5 6 20 10 Pancharatnam phase φp 0 X ax is (µ m) − 10 − 20 − 25 − 20 − 15 − 10 − 5 0 5 10 15 20 25 Ya x is (µm ) 0 1 2 3 4 5 6 100 50 Pancharatnam phase φp 0 X ax is (µ m) − 50 − 100 − 100 − 80 − 60 − 40 − 20 0 20 40 60 80 100 Ya x is (µm ) 18!Phase'ramp:'SGVC4'with'curves
' 51.2'x'51.2'µm' dx'='dy'='0.1'µm' dz'='0.2'µm' 102.4)x)102.4)µm) dx'='dy'='0.1'µm' dz'='0.2'µm' ' 0 1 2 3 4 5 6 20 10 Pancharatnam phase φp 0 X ax is (µ m) − 10 − 20 − 25 − 20 − 15 − 10 − 5 0 5 10 15 20 25 Ya x is (µm ) 0 1 2 3 4 5 6 50 Pancharatnam phase φp 0 X ax is (µ m) − 50 − 50 − 40 − 30 − 20 − 10 0 10 20 30 40 50 Ya x is (µm ) !)Better)on)the)xAaxis,)but)much)worse)on)the)yAaxis)WP3: performance estimation
Vortex'Phase'Mask:'Charge'2'
f' f' f' f' f' f' f' 3' Min:'2.33*10T11'' Max:2.23*10T3'Entrance*pupil* Before*Lyot*Stop* Detector*
19 3D FDTD
simula@ons
AO residuals + op@cal design
WP3: performance testing
•
VODCA: the Vortex Op@cal Demonstrator for
Coronagraphic Applica@ons
•
AGPM tes@ng + in-‐lab valida@on of new concepts
20
Design
VODCA Layout
WP3: post-‐corono sensing
•
At Lyot stop or on the science camera
•
See talk by Elsa Huby this axernoon
WP3: quantum properties
22
No OAM No OAM
