TPF-I SWG Report - Exoplanet Exploration Program - NASA

C HAPTER 6
Figure 6-1. The State of the Art of Nulling Interferometry: Laboratory results showing null depth as a
function of bandwidth for experiments at visible, infrared, and mid-infrared wavelengths. Results that are
plotted with a zero bandwidth are laser measurements. Almost all results are limited to a singlepolarization
input. All but one of the results are from two-beam nulling interferometers. The result by
Martin et al. (2005) is from the four-beam Planet Detection Testbed, described later in this Section. The
result by Gappinger (2006) is an unpublished result from the Achromatic Nulling Testbed. The result by
Peters (2007) is a preliminary and unpublished result from the Adaptive Nuller. The literature references,
where available, are listed at the end of this chapter.
TPF-I are the experiments that have been conducted at mid-infrared wavelengths, which are indicated by
the red circles in the plot.
From the results to date, we can draw the following conclusions.
1. Experiments have shown that achromatic effects (predominantly pathlength variations) can be
controlled in the lab at a level that allows rejection ratios better than 1,000,000:1 to be achieved
repeatedly. This level of performance exceeds the requirements for TPF-I. Narrow-bandwidth
laser nulls have been attained with mid-infrared rejection ratios of 2,000,000:1 and at visible
wavelengths of 10,000,000:1.
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