Cheapest nuller in the World: Crossed beamsplitter cubes François Hénault Institut de Planétologie et d’Astrophysique de Grenoble, Université Joseph Fourier, CNRS, B.P. 53, 38041 Grenoble – France Alain Spang Laboratoire Lagrange, Université de Nice-Sophia Antipolis, CNRS, Observatoire de la Côte d’Azur, B.P. 4229, 06304 Nice – France Cube 2
Principle
Cube 1 Beam 1
Beam 3
Y’ SubPupil 2
X’
0
SubPupil 1
Z SubPupil 3
Y’ Polarization Y’
0
X’
π
π
•
0
π X’
SubPupil 4
•
X’
•
0
π
•
Cubes polarization model
U
1 arcsec
1 arcsec
have their semi-reflective (SR) perpendicular one to the other The input beams propagates parallel to both cubes SR layers It is spitted into four parallel beams, being recombined axially A “null” is created at the focal plane centre It is independent of polarization orientation and of wavelength (at least theoretically) This is actually an Achromatic phase shifter
U
1 arcsec
1 arcsec V
Unpolarized
1 arcsec
Beam 4
X’ Polarization Y’
Y’ Polarization V
• Two “crossed” beamsplitter cubes
Beam 2
Y’
X’ Polarization V
U
1 arcsec
Nulling maps at image plane
Secondary Mirror
Advantages
Monolithic telescope
(P)
Converging optics Diverging optics Fold mirror Beamsplitter or dichroïcs
Primary Mirror
Relay optics
Wavefront sensor
Crossedcubes nuller
Multi-axial combiner (exit pupil plane)
P’1
O’
(P’)
P’2 F’
B’ Focal plane
O” Z
X”
Simple, compact, low mass and volume Reasonable manufacturing tolerances Potentially not expensive High throughput, close to maximum Can be implemented into a nulling coronagraph telescope or a sparseaperture nulling interferometer • Very small Inner working angle (IWA) when used as a coronagraph • Capacity for fringes rotation and baseline modulation • Good candidate for future space missions characterizing extra-solar planets atmospheres • • • • •
B
P1
O
P2
Telescope 1
Telescope 2
Relay optics 1
Crossedcubes nuller
(P)
Relay optics 2
Fringe tracker 2-3 Tip-tilt sensors
Fringe tracker 1-4 Tip-tilt sensors
Fringe tracker 14-23
(P’) O’
O”
F’
Focal plane Z
Contacts
[email protected] [email protected]
