Shearing interferometry via geometric phase

International audienceWe propose an approach based on geometric phase for performing several types of shearing interfer-ometry through a robust, compact, common-path setup. The key elements are two identical parallel plates with spatially-varying birefringence distributions , which perform the shearing by writing opposite geometric phases on the two circular polarization components of the linearly polarized incident wavefront. This setup allows the independent control of the shearing magnitude and relative phase of the two wavefront replicas. The approach is first illustrated for the simplest case of lateral shearing, and then extended to other ge-ometries where the magnitude and direction of the shear vary smoothly over the wavefront. http://dx.doi.org/10.1364/optica.XX.XXXXXX Introduction-Shearing interferometry is a widespread technique for analyzing optical wavefronts. Its main feature is that of not requiring a known reference; instead, two replicas of the test wavefront are made to interfere after being displaced laterally (lateral shearing), resized differently (radial shearing), or mutually rotated (azimuthal shearing) [1, 2]. The interferogram's interpretation depends not only on the type of shearing but also on its amount-the shear distance (SD)-, and the relative phase difference between the replicas-the shear phase (SP). In typical common-path layouts based on Snell refraction/reflection, such as shear plates or more complex setups [3-5], the SD and SP are coupled and depend on the position or orientation of an optical element. Several mechanisms have been suggested to control SD and SP independently [1, 6-9]. In particular, polarization-based shearing naturally presents this feature because the two replicas are orthogonally polarized. However, polarization-based shearing interferometers often require several optical components and tend to be bulky or expensive [10-14]. More recent propo