Eclipse apodization: realization of occulting spots and Lyot masks

A key element in the Eclipse coronagraph is the apodized occulting spot. For exo-planet detection in the presence of a sun-like star, the specification for intensity transmittance at the center of the spot is less than 1×10-8. It must also taper smoothly with a desired functional form to avoid diffraction artifacts in the angular region of planet detection. From a fabrication point of view, these requirements are very challenging. A candidate technology for fabricating such spots is electron-beam exposure of high-energy beam sensitive (HEBS) glass (a product of Canyon Materials, San Diego, CA). In this work, we have calibrated HEBS glass optical density as a function of electron-beam exposure and attained optical densities up to 7.66 without saturation. We then fabricated occulting spots having various functional forms including circular Gaussian, one-dimensional sinc2, and circular sinc2. Preliminary quantitative analysis of the circular sinc2 occulting spot is encouraging.