S2. Single-nuller Configuration
Figure S1 is a block diagram of an interferometer configuration using an achromatic nulling beam combiner to combine light from the two apertures. The nulling combiner is similar in principle to a Bracewell interferometer that combines the light from the two apertures out-of-phase in order to provide starlight cancellation. However, the achromatic nulling configuration uses polarization rather than a physical path delay to generate an achromatic 180o phase shift, allowing nulling over a wide spectral band. The delay lines in the figure maintain equality between the two arms of the interferometer. The depth of the achieved null is limited by the size of the source as well as various instrumental and residual atmospheric errors, as discussed in the next section.
Last updated March-06-1998