On-sky Demonstration of Second-stage Wave-front Control with a Photonic Lantern

Abstract Ground-based direct imaging of exoplanets at high contrast requires precise correction of atmospheric turbulence using adaptive optics (AO). The planet-to-star contrast ratio at small angular separations from the host star is often limited by non-common-path aberrations (NCPAs) that are seen only in the science plane. The photonic lantern (PL) can be used to sense aberrations at the final science imaging plane. This enables a two-stage wave-front control architecture, in which the first-stage wave-front sensor senses atmospheric turbulence and the PL senses NCPAs and other aberrations not seen by the first stage. We demonstrate closed-loop control of residual wave-front errors using a nondispersed PL after first-stage AO correction on the Shane 3 m telescope at Lick Observatory. Our results show that nondispersed PLs can be used for second-stage wave-front sensing, enabling performance improvements via minimally invasive retrofits to existing AO systems.