Polarimetric imaging device optimised in relation to polarisation contrast

摘要

The polarimetric imaging device comprises a structure having multi-well quantum structure operating on intersubband transitions by absorption of a radiation at a lambda wavelength. The structure comprises an elementary pixel matrix (Eij) for detection, where the matrix is organized into subsets of four elementary pixels. A first polarimetric pixel comprises a first diffraction grating (R(P1)) sensitive to a first polarization. A second polarimetric pixel comprises a second diffraction grating (R(P2)) sensitive to a second orthogonal polarization at the first polarization. The polarimetric imaging device comprises a structure having multi-well quantum structure operating on intersubband transitions by absorption of a radiation at a lambda wavelength. The structure comprises an elementary pixel matrix for detection, where the matrix is organized into subsets of four elementary pixels. A first polarimetric pixel comprises a first diffraction grating (R(P1)) sensitive to a first polarization. A second polarimetric pixel comprises a second diffraction grating (R(P2)) sensitive to a second orthogonal polarization at the first polarization. A third polarimetric pixel comprises a third diffraction grating (R(P3)) sensitive to a third polarization oriented along an angle between the first and second polarizations. The fourth pixel comprises a fourth diffraction network (R(2D)) non selective in polarization. A unit is arranged for processing signals recovered at the level of pixels for detection. The unit for processing signals comprises a unit for adding signals obtained respectively from the first, second and third pixel for detection and a unit for subtracting the signal obtained from the fourth detection pixel. The third pixel comprises a diffraction grating sensitive to a third polarization oriented at an angle of 45[deg] . The first, second and third diffraction networks are one-dimensional networks comprising lamellar patterns. A stack of layers is produced on the surface of a substrate, and comprises a multiwell quantum structure and external layers. The lamellar patterns are etched in an external layer. The multiwell quantum structure is composed of alternating doped gallium arsenide layers and undoped gallium aluminum arsenic layers. The outer layers are of ohmic contact layers made of more strongly doped gallium arsenide than those constituting the multiwell quantum structure. A transparent substrate is present at the wavelength of incident radiation. A reflective layer is present at the surface diffraction networks to operate the detector by reflection.