title: OPD measurement and dispersion reduction in a monolithic interferometer.
abstract: We describe a white light fringe scanning and pupil bisecting method of measuring the optical path difference (OPD) between arms of a monolithic nulling interferometer that is designed to enable direct imaging of planetary companions and the environments around nearby stars. This measurement is used to determine the differential thicknesses of optically contacted compensator plates used to reduce OPD, which can drastically impair the optic's performance in broadband light. By making this correction, we were able to reduce the initial OPD from 949+/-44 nm to 63+/-10 nm. In the absence of any other asymmetries that can compromise the null, such a correction corresponds to an increase in an R-band (lambda(c) = 648 nm) nulling bandpass from monochromatic to 25%.
authors: Center for Space Physics, Boston University, 725 Commonwealth Avenue, Boston, MA 02215, USA. bahicks@bu.edu
authors: Brian
authors: B
authors: Hicks
authors: Timothy
authors: T
authors: Cook
authors: Benjamin
authors: B
authors: Lane
authors: Supriya
authors: S
authors: Chakrabarti
mesh_terms: D004867:Equipment Design; D007368:Interferometry / Q000295:instrumentation; D008027:Light; D055095:Optics and Photonics; D012031:Refractometry / Q000379:methods*