Experimental evaluation of achromatic phase shifters for mid-infrared starlight suppression
Abstract
Phase shifters are a key component of nulling interferometry, one of the potential routes to enabling the measurement of faint exoplanet spectra. Here, three different achromatic phase shifters are evaluated experimentally in the mid-infrared, where such nulling interferometers may someday operate. The methods evaluated include the use of dispersive glasses, a through-focus field inversion, and field reversals on reflection from antisymmetric flat-mirror periscopes. All three approaches yielded deep, broadband, mid-infrared nulls, but the deepest broadband nulls were obtained with the periscope architecture. In the periscope system, average null depths of 4×10-5 were obtained with a 25% bandwidth, and 2×10-5>/SUP> with a 20% bandwidth, at a central wavelength of 9.5 μm. The best short term nulls at 20% bandwidth were approximately 9×10-6, in line with error budget predictions and the limits of the current generation of hardware.
- Publication:
-
Applied Optics
- Pub Date:
- February 2009
- DOI:
- 10.1364/AO.48.000868
- Bibcode:
- 2009ApOpt..48..868G