The Space Coronagraph Optical Bench (SCoOB): 5. End-to-end simulations of polarization aberrations

TL;DR

This paper models polarization aberrations in a space-based high-contrast imaging system, revealing their impact on contrast performance and identifying key sources of aberrations affecting exoplanet imaging.

Contribution

It provides the first end-to-end simulation of polarization aberrations in a high-contrast imaging testbed, incorporating measured retardance maps and analyzing their effects on contrast.

Findings

Polarization aberrations cause brighter speckles limiting contrast to 1e-9.

Mean contrast remains unaffected by polarization aberrations, but small inner working angles are impacted.

VVC and QWP retardance errors have a greater effect on contrast than polarization aberrations.

Abstract

Polarization aberrations originating from the telescope and high-contrast imaging instrument optics introduce polarization-dependent speckles and associated errors in the image plane, affecting the measured exoplanet signal. Understanding this effect is critical for future space-based high-contrast imaging instruments that aim to image the Earth analogs with 1e-10 raw contrast and characterize their atmospheres. We present end-to-end modeling of the polarization aberrations for a high-contrast imaging testbed, SCoOB. We use a vector vortex coronagraph (VVC) as the focal plane mask, incorporate polarization filtering, and estimate the peak contrast in the dark hole region. The dominant polarization aberrations in the system are retardance defocus and tilt due to the OAPs and fold mirrors. Although the mean contrast in the dark hole region remains unaffected by the polarization aberrations, we see brighter speckles limiting the contrast to 1e-9 at smaller inner working angles. We extend the simulations using the measured retardance maps for the VVC. We find that the mean contrast in SCoOB is more sensitive to the VVC and the QWP retardance errors than the polarization aberrations.