The Annular Groove Phase Mask coronagraph (AGPM) is an intrinsically achromatic vectorial vortex. It consists of integrated subwavelength optical elements whose space-variant polarization properties can be engineered and optimized to synthesize one of the theoretically most efficient coronagraphs. This paper briefly recalls the principles of the AGPM, presents the benefit of its implementation inside a Polarimetrie differential imager, realistic numerical simulations assessing its performances, as well as the current status of the near-infrared and visible prototype manufacturing operations.

We propose a new family of achromatic phase shifters for infrared nulling interferometry. These key optical components can be seen as optimized Fresnel rhombs, using the total internal reflection phenomenon, modulated or not. The total internal reflection indeed comes with a phase shift between the polarization components of the incident light. We propose a solution to implement this vectorial phase shift between interferometer arms to provide the destructive interference process needed to disentangle highly contrasted objects from one another. We also show that, modulating the index transition at the total internal reflection interface allows compensating for the intrinsic material dispersion in order to make the subsequent phase shift achromatic over especially broad bands. The modulation can be induced by a thin film of a well-chosen material or a subwavelength grating whose structural parameters are thoroughly optimized. We present results from theoretical simulations together with preliminary fabrication outcomes and measurements for a prototype in Zinc Selenide.

We propose a new family of achromatic phase shifters that uses the modulated total internal reflection (TIR) phenomenon. These components can be seen as enhanced Fresnel rhombs for infrared applications like nulling interferometry and polarimetry. The TIR phenomenon comes with a differential phase shift between the polarization components of the incident light. Modulating the index transition at the TIR interface allows compensating for the intrinsic material dispersion in order to make the subsequent phase shift achromatic over broad bands. The modulation can be induced by a thin film of a well-chosen medium or a subwavelength grating whose parameters are specially optimized. We present results from theoretical simulations together with preliminary fabrication outcomes.