Lyot Coronagraphs with Band-Limited Masks - Exoplanet ...

Exoplanet Detection with Coronagraphs 2006
Lyot Coronagraphs with Band-Limited Masks
DISCUSSION
Relative to other coronagraph architectures, band-limited masks offer modest throughput, excellent robustness to
dynamic aberrations, low optical complexity, and unrivaled experimental verification. The experimental
verification, and the maturity of the models that accompany band-limited masks, make this approach relatively
low-risk compared to other architectures, at their current state of development.
The theoretical band-limited mask throughput is better than that of shaped pupils, similar to that of the visible
nuller, and worse than those of optical vortices, phase-induced amplitude apodization, or external occulters. The
diffractive efficiency (PSF width) compares in the same ways with other architectures.
The construction of occulting masks accurate enough in phase and OD for broadband performance at TPF-C
levels has not been demonstrated, but is not expected to lie outside of current state-of-the-art. Current bandlimited
masks have achieved the best experimental contrast to date, below 10 -9 monochromatically. The
requirements on other optics are the same as for other coronagraph architectures, with the exception of the
external occulter (which has very different optical requirements).
To summarize, band-limited masks have modest theoretical performance, but offer the most evidence of any
architecture to date that they will ultimately be capable of delivering TPF-C performance, a challenging task.
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