Circular Polarimetric Imaging with a Metamaterial Integrated Long-Wavelength Infrared Focal Plane Array

Long-wavelength infrared (LWIR) circular polarimetric imaging plays an important role in many areas. The immediacy of polarimetric imaging and the miniaturization of devices drive considerable efforts to division-of-focal-plane-array (DoFPA) circular polarimeters. However, the realization of such detectors is hampered by low polarization discrimination, reduced absorption in the detection material, and fabrication complexity. The situation becomes more serious in the LWIR range since the pixel size is only a few wavelengths of the incident light. Here, a quantum well infrared photodetector based LWIR DoFPA circular polarimeter featuring a 320 × 256 pixel array integrated with a chiral meta-mirror array is established. The spectral range of this detector is from 10 to 11 µm. Taking advantage of the dual polarization selection, a CPER of 23.3 is achieved for the pixels integrated with the same chiral meta-mirror structure, and a CPER of 5.67 for the pixels integrated with left- and right-handed chiral meta-mirror structures in a checkerboard pattern. The peak responsivity is improved by a factor of 9.13 compared to a standard reference device. With the LWIR DoFPA circular polarimeter, Stokes parameter S₃ imaging is achieved with a noise equivalent S₃ difference of 1.16×10^-4, and demonstrate background suppression and target highlighting.