Normalized to: K.
[1]
oai:arXiv.org:1009.1015 [pdf] - 223674
Design, analysis, and testing of a microdot apodizer for the apodized
pupil Lyot coronagraph (Research note). III. Application to extremely large
telescopes
Submitted: 2010-09-06
The apodized-pupil Lyot coronagraph is one of the most advanced starlight
cancellation concepts studied intensively in the past few years. Extreme
adaptive optics instruments built for present-day 8m class telescopes will
operate with such coronagraph for imagery and spectroscopy of faint stellar
companions. Following the development of an early demonstrator in the context
of the VLT-SPHERE project (~2012), we manufactured and tested a second APLC
prototype in microdots designed for extremely large telescopes. This study has
been conducted in the context of the EPICS instrument project for the
European-ELT (~2018), where a proof of concept is required at this stage. Our
prototype was specifically designed for the European-ELT pupil, taking its
large central obscuration ratio (30%) into account. Near-IR laboratory results
are compared with simulations. We demonstrate good agreement with theory. A
peak attenuation of 295 was achieved, and contrasts of 10^-5 and 10^-6 were
reached at 7 and 12 lambda/D, respectively. We show that the APLC is able to
maintain these contrasts with a central obscuration ratio of the telescope in
the range 15% to 30%, and we report that these performances can be achieved in
a wide wavelength bandpass (BW = 24%). In addition, we report improvement to
the accuracy of the control of the local transmission of the manufactured
microdot apodizer to that of the previous prototype. The local profile error is
found to be less than 2%. The maturity and reproducibility of the APLC made
with microdots is demonstrated. The apodized pupil Lyot coronagraph is
confirmed to be a pertinent candidate for high-contrast imaging with ELTs.