SPHERE IFS: The spectro differential imager of the VLT for exoplanets search

SPHERE is an exo-solar planet imager, which goal is to detect giant exo-solar planets in the vicinity of bright stars and to characterize them through spectroscopic and polarimetric observations. It is a complete system with a core made of an extreme-Adaptive Optics (AO) turbulence correction, pupil tracker and interferential coronagraphs. At its back end, a differential dual imaging camera and an integral field spectrograph (IFS) work in the Near Infrared (NIR) Y, J, H and Ks bands (0.95 - 2.32 mu m) and a high resolution polarization camera covers the visible (0.6 - 0.9 mu m). The IFS is a low resolution spectrograph (R similar to 50 and R similar to 30) which works in the near IR (0.95-1.7 microns), an ideal wavelength range for the detection of planetary features. In our baseline design the IFU is a new philosophy rnicrolens array of about 145x145 elements designed to reduce as low as possible the contrast. The IFU will cover a field of view of about 1.8 x 1.8 square arcsecs reaching a contrast of 10(-7), giving an high contrast and high spatial resolution "imager" able to search for planet well inside the star PSF.