Experimental results from a visible ing interferometer

Direct detection of planets around nearby stars requires the suppression of the parent starlight to many orders of magnitude (9 orders for visible, 6 for the MidIR). Myriad techniques have been proposed to accomplish this task including: pupil masking, coronagraphy and ing interferometry. All of these techniques are currently undergoing rapid development. Nulling interferometry in the visible part of the spectrum is viewed as particularly difficult for two reasons: 1) fundamentally, the planet/star contrast is greater by roughly three orders of magnitude and 2) practically speaking, the expected residual fabrication errors produce larger phase error at shorter wavelengths. For these reasons, ing interferometry experiments are currently planned for 7-12 μm, where both of these factors are mitigated. However, progress may not be smooth at these mid IR wavelengths due to the lack of readily available components, and the difficulty of working with a large thermal background. Therefore, ing interferometry in the visible continues to be compelling, particularly if it can be done deeply. Our team has proposed an instrument known as a visible ing coronagraph. This instrument resides behind a single aperture and provides deep and stable interferometric s that are consistent with the requirements for direct detection. Its two key components are a ing interferometer and a single mode fiber array (for reducing scattered light after the interferometer). In this paper, we first summarize the benefits of a ing coronagraph. We subsequently show experimental measurements made with the visible ing interferometer. We have demonstrated the feasibility of the shearing ing concept, and are the first to control the with a (laser) metrology system. As a result of these experiments, the visible ing coronagraph continues to be a compelling technique for planet detection and spectroscopy.