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We investigate the effects of the parasitic phase of imperfect band-limited occulting masks on the broadband contrast performance of a high-contrast imaging system through modeling and simulations. We also examine the effects of the phase and the optical-density dispersions of occulting masks whose parasitic phase has been compensated at the center wavelength but is nonzero at other wavelengths. Two types of occulting masks are considered: gray-scale masks such as those made on a high-energy beam-sensitive glass, and recently proposed spatially profiled metal masks, both having 1D [Sinc.sup.2] (linear-[Sinc.sup.2]) amplitude transmission coefficient ([Sinc.sup.4] intensity transmittance) profiles. We determine the conditions for obtaining 1 x [10.sup.-9] and 1 x [10.sup.-10] contrast values with a light centered at a 785 nm wavelength and having a 10% bandwidth in a coronagraphic telescope having ideal optical surfaces but imperfect band-limited image-plane occulting masks. OCIS codes: 110.6770, 220.4830.

A method for the control of polarization for a broadband dichroic filter was reported and some design examples were elaborated. This method could be applied over a wide range of wavelengths and a wide range of polarizations in the transmission region. A nonpolarizing broadband dichroic filter and a broadband dichroic filter with certain polarization were designed and fabricated by electron beam evaporation with ion beam assisted deposition. The experimental spectral performances showed good agreement with their theoretical curves. In addition, the application of the method was discussed. OCIS codes: 310.6860, 350.2460, 260.5430.