Common-path lateral-shearing nulling interferometry with a Savart plate for exoplanet detection

We propose a common-path lateral-shearing nulling interferometer for direct detection of exoplanets. A Savart plate is placed between crossed polarizers to produce a lateral shear and realize fully achromatic and highly stable nulling interference for starlight. We construct a double-shearing interferometer using two Savart plates for implementing orthogonal x and y shears. A laboratory demonstration is carried out using a broadband light source with a band-width of Delta lambda/lambda(0) = 0.33 (Delta lambda = 0.2 mu m and lambda(0) = 0.6 mu m). As a result, achieved extinction levels are 4 x 10(-4) at peak and 4 x 10(-7) at 10 lambda(0)/D(L) (D(L) is the diameter of a Lyot stop). (C) 2010 Optical Society of America