Planet detection in visible light with a single aperture telescope and nulling coronagraph

Abstract

This paper describes the latest progress for visible direct detection of Earth like extrasolar planets using a nulling coronagraph instrument behind a 4m class telescope. Such a system is capable of satisfying the scientific objectives of the Terrestrial Planet Finder mission In our design, a 4 beam nulling interferometer is synthesized from the telescope pupil, producing a very deep null proportional to θ⁴ which is then filtered by a coherent array of single mode fibers to suppress the residual scattered light. With diffraction limited telescope optics and similar quality components in the optical train (λ/20), suppression of the starlight to 10^-10 is achievable. Such a telescope with this nulling interferometer as back-end instrument can image and detect planets, or provide the input to a low resolution spectrometer. Shown are key features of this system in a space mission, latest results of laboratory measurements demonstrating achievable null depth, and progress toward fabrication of coherent single mode fiber arrays.