The space coronagraph optical bench (SCoOB): 4. vacuum performance of a high contrast imaging testbed

TL;DR

The paper presents the latest vacuum performance results of the SCoOB high-contrast imaging testbed, demonstrating starlight suppression at contrast levels below 10^-8 in a space-like environment with various optical configurations.

Contribution

It reports the integration of new components and the achievement of record contrast performance in a vacuum environment for a space coronagraph testbed.

Findings

Achieved contrast of 2.2×10^-9 in a half-sided dark hole.

Demonstrated stable jitter below 3×10^-3 λ/D.

Operated successfully over 500-650 nm bandwidths.

Abstract

The Space Coronagraph Optical Bench (SCoOB) is a high-contrast imaging testbed built to demonstrate starlight suppression techniques at visible wavelengths in a space-like vacuum environment. The testbed is designed to achieve ${<}10^{-8}$ contrast from $3-10\lambda/D$ in a one-sided dark hole using a liquid crystal vector vortex waveplate and a 952-actuator Kilo-C deformable mirror (DM) from Boston Micromachines (BMC). We have recently expanded the testbed to include a field stop for mitigation of stray/scattered light, a precision-fabricated pinhole in the source simulator, a Minus K passive vibration isolation table for jitter reduction, and a low-noise vacuum-compatible CMOS sensor. We report the latest contrast performance achieved using implicit electric field conjugation (iEFC) at a vacuum of ${\sim}10^{-6}$ Torr and over a range of bandpasses with central wavelengths from 500 to 650nm and bandwidths (BW) from $\ll 1\%$ to 15\%. Our jitter in vacuum is $<3\times10^{-3} \lambda/D$, and the best contrast performance to-date in a half-sided D-shaped dark hole is $2.2\times10^{-9}$ in a $\ll 1 \%$ BW, $4\times10^{-9}$ in a 2\% BW, and $2.5\times10^{-8}$ in a 15\% BW.