29-06-2022 #
PIAA Coronagraph #
A new Coronagraph has been studied for RISTRETTO and shows very promizing characteristics. It is a PIAA, based coronagraph, that using distortion change the illumination of the pupil of the instrument from a top-hat (minus obstruction and spiders) to a truncated gaussian.
The gaussian profile allow to increase significantly the coupling into the fibers for the planetary signal, the truncation allow for the nulling of the stellar signals. In addition it keeps the circular symetry.
Broad band performances are achiveable:
It is the best possible solution for our figure of merit: the product of the transmission of the planetary signal and the achievable contrast.
We thank a lot Olivier Guyon et al and Patrice Martinez et al for the fruitful discussion the PIAA concepts.