  Spectro-photometry of debris disks in total intensity and polarimetry can
provide new insight into the properties of the dust grains therein (size
distribution and optical properties).
  We aim to constrain the morphology of the highly inclined debris disk HD
32297. We also intend to obtain spectroscopic and polarimetric measurements to
retrieve information on the particle size distribution within the disk for
certain grain compositions.
  We observed HD 32297 with SPHERE in Y, J, and H bands in total intensity and
in J band in polarimetry. The observations are compared to synthetic models of
debris disks and we developed methods to extract the photometry in total
intensity overcoming the data-reduction artifacts, namely the self-subtraction.
The spectro-photometric measurements averaged along the disk mid-plane are then
compared to model spectra of various grain compositions.
  These new images reveal the very inner part of the system as close as 0.15".
The disk image is mostly dominated by the forward scattering making one side
(half-ellipse) of the disk more visible, but observations in total intensity
are deep enough to also detect the back side for the very first time. The
images as well as the surface brightness profiles of the disk rule out the
presence of a gap as previously proposed. We do not detect any significant
asymmetry between the northeast and southwest sides of the disk. The spectral
reflectance features a "gray to blue" color which is interpreted as the
presence of grains far below the blowout size.
  The presence of sub-micron grains in the disk is suspected to be the result
of gas drag and/or "avalanche mechanisms". The blue color of the disk could be
further investigated with additional total intensity and polarimetric
observations in K and H bands respectively to confirm the spectral slope and
the fraction of polarization.
