1 Faint Near-Neighbor Detection with a Fiber Nuller

Abstract—Direct detection of nearby extra-solar planets via their thermal infrared emission can be carried out by means of infrared nulling interferometry. In this approach, the central star is nulled, while the emission from off-axis sources is transmitted and modulated by the rotation of the off-axis fringes. Because of the high contrasts involved, and the novelty of the measurement technique, it is essential to gain experience with this technique before launch of potential missions such as the Terrestrial Planet Finder Interferometer (TPF-I). Here a simple ground-based experiment that can test the essential aspects of the TPF signal measurement and image reconstruction approaches is described. It is based on generating a rotating interferometric baseline within the pupil of a large single-aperture telescope. This approach should allow for testing of proposed signal extraction algorithms for the detection of single and multiple near-neighbor companions, and also allows for the development and deployment of potential nulling beam combiners. Interestingly, such an interferometric nuller on a single aperture telescope also functions as a coronagraph with a rather small inner working distance. Such a “nulling coronagraph ” can thus outperform classical coronagraphs in certain respects. 1