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

摘要

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 bandwidth of (DELTA)(lambda)/(lambda)_(0) velence 0.33 ((DELTA)(lambda) velence 0.2 (mu)m and lambda_(0) velence 0.6 (mu)m). As a result, achieved extinction levels are 4 X 10~(-4) at peak and 4 X 10~(-7) at 10lambda_(0)/D_(L) (D_(L) is the diameter of a Lyot stop).