Achromatic Phase Shifters are mandatory components in the field of nulling interferometry and phase coronagraphy. Indeed, in order to detect faint objects (e.g. exo-planets) around a central bright star, one must attenuate the latter by all means. To do this, the most efficient way is to “create” a destructive interference on the blinding light. This technique is called nulling and is common to the two fields mentioned above; the first with several telescopes, the second with only a single aperture. How does it work? The incoming light from the central object is divided into several beams on which one applies a differential π phase shift by means of these so-called phase shifters. Then, when the beams are properly recombined together, they simply subtract from each other. “Achromatic” means that we can apply this process over a large spectral bandwidth. This quality will not only be required for the detection and characterization of exo-planets but also for several other astrophysical objects involving huge contrasts like dust shells around young bright stars, AGN,... The proposed birefringent phase shifters and the original implementation schemes we suggest should provide flexible and powerful solutions for these purposes.

Achromatic lens

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OPTOPUS observations of Halley’s comet

The Messenger (1986)

G. Lund Jean Surdej

Halley's Comet

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A generalized method for deriving mass-loss rates: The first order moment of unsaturated P Cygni line profiles

Astrophysics and Space Science (1983)

Jean Surdej

Line (geometry)

Limb darkening

10.1007/bf00650064

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Formation of resonance doublet profiles in rapidly expanding envelopes

Astrophysics and Space Science (1980)

Jean Surdej

Envelope (radar)

10.1007/bf00642369

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Simultaneous Photometry and Spectroscopy of the B2(e) Variable Star HD 4567

International Astronomical Union Colloquium (1979)

R. Barbier N. Klutz Anna Surdej Jean Surdej Jean-Pierre Swings

Light variations are observed for HD 45677 in the visible, if they are due to obscuration by circumstellar patchy dust clouds, part of the stellar UV and visible radiations are back-scattered inside the extended atmosphere surrounding the star. The excitation of all atoms and ions in the envelope is thus affected, and the result is seen most for the atoms moving towards the observer: the intensity variations of the blue emission wings of the Balmer lines in opposite phase with simultaneous variations of the stellar flux are therefore understandable.

Balmer series

Circumstellar envelope

10.1017/s0252921100073619

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