Issue |
A&A
Volume 488, Number 3, September IV 2008
|
|
---|---|---|
Page(s) | 1159 - 1165 | |
Section | Astronomical instrumentation | |
DOI | https://doi.org/10.1051/0004-6361:200810469 | |
Published online | 23 July 2008 |
Optical vortices with starlight
1
Dipartimento di Astronomia, Università di Padova, vicolo dell'Osservatorio 3, 35122 Padova, Italy e-mail: gabriele.anzolin@unipd.it
2
INAF-Osservatorio Astronomico di Capodimonte, salita Moiariello 16, 80131 Napoli, Italy
Corresponding author: G. Anzolin, gabriele.anzolin@unipd.it
Received:
26
June
2008
Accepted:
18
July
2008
Aims. In this paper we present our first observations at the Asiago 122 cm telescope
of optical vortices generated with starlight beams.
Methods. We used a fork-hologram blazed at the first diffraction order as a phase modifying device. The multiple system Rasalgethi (α Herculis) in white light and the single star Arcturus (α Bootis) through a 300 Å bandpass were observed using a fast CCD camera. In the first case we could adopt the Lucky Imaging approach to partially correct for seeing effects.
Results. For both stars, the optical vortices could be clearly detected above the smearing caused by the mediocre seeing conditions. The profiles of the optical vortices produced by the beams of the two main components of the α Her system are consistent with numerically simulated on-axis and off-axis optical vortices. The optical vortices produced by α Boo can also be reproduced by numerical simulations. Our experiments confirm that the ratio between the intensity peaks of an optical vortex can be extremely sensitive to off-axis displacements of the beam.
Conclusions. Our results give insights for future astronomical applications of optical
vortices both for space telescopes and ground-based telescopes with good seeing
conditions and adaptive optics devices. The properties of optical vortices can be
used to perform high precision astrometry and tip/tilt correction of the
isoplanatic field. We are now designing a optical vortex coronagraph
around a continuous spiral phase plate. We also point out that optical vortices
could find extremely interesting applications also in the infrared and radio
wavelengths.
Key words: instrumentation: miscellaneous / techniques: high angular resolution / atmospheric effects
© ESO, 2008
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