A mid-infrared broadband achromatic astronomical beam combiner for nulling interferometry

摘要

Integrated optic beam combiners offer many advantages over conventional bulkoptic implementations for astronomical imaging. To date, integrated optic beamcombiners have only been demonstrated at operating wavelengths below 4 microns.Operation in mid-infrared wavelength region, however, is highly desirable. Inthis paper, a theoretical design technique based on three coupled waveguides isdeveloped to achieve fully achromatic, broadband, polarization-insensitive,lossless beam combining. This design may make it possible to achieve the verydeep broadband nulls needed for exoplanet searching.