Instantaneous phase retrieval with the vector vortex coronagraph - Theoretical and optical implementation

Coronagraphs are used as high-contrast imaging tools. However, it is well-known that the achievable contrast is primarily limited by wavefront aberrations in the optical train. Various kinds of devices and methods have been proposed to correct and calibrate these errors and, hence, improve the efficiency of coronagraphs. Here, we present an innovative idea that allows instantaneous measuring of the phase and the amplitude of residual stellar speckles in coronagraphic images. The technique is based on the unique polarization properties of the vector vortex coronagraph, which serves as a new type of phase diversity (POAM diversity), as well an extension of the Nijboer-Zernike theory of aberrations. We also propose and discuss a simple practical optical implementation of the technique, which only requires polarization splitting at the back-end of any existing vector vortex coronagraph systems.