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

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 3-10λ/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 ~10⁻⁶ Torr and over a range of bandpasses with central wavelengths from 500 to 650nm and bandwidths (BW) from 1% to 15%. Our jitter in vacuum is <3×10⁻³ λ/D, and the best contrast performance to-date in a half-sided D-shaped dark hole is 2.2×10⁻⁹ in a 1 % BW, 4×10⁻⁹ in a 2% BW, and 2.5×10⁻⁸ in a 15% BW.