Toward 10 ¹⁰ contrast for terrestrial exoplanet detection: Demonstration of wavefront correction in a shaped-pupil coronagraph

The Shaped Pupil Coronagraph (SPC) is a high-contrast imaging system pioneered at Princeton for detection of extrasolar earthlike planets. It is designed to achieve 10 ^-10 contrast at an inner working angle of 4λ/D. However, a critical requirement in attaining this contrast level in practice is the ability to control wavefront phase and amplitude aberrations to at least λ/10 ⁴ in rms phase and 1/1000 rms amplitude, respectively. Furthermore, this has to be maintained over a large spectral band. The High Contrast Imaging Testbed (HCIT) at the Jet Propulsion Lab (JPL) is a state-of-the-art facility for studying high contrast imaging systems and fine wavefront control methods. It consists of a vacuum chamber containing a configurable coronagraph setup with a Xinetics deformable mirror. In this paper, we present the results of testing Princeton's SPC in JPL's HCIT. In particular, we present the achievement of 4×10 ^-8 contrast using a speckle nulling algorithm, and demonstrate that this contrast is maintained across wavelengths of 785, 836nm, and for broadband light having 10% bandwidth around 800nm.