Recently, researchers Lu Wei, Chen Xiaoshuang, Zhou Jing, and collaborators at the National Key Laboratory of Infrared Science and Technology have pioneered the development of a long-wave infrared (LWIR) circularly polarized focal plane array (FPA) detector. Through photon-electron co-design and nanoscale perforation alignment processes, they adressed three major bottlenecks in integrated circularly polarized detectors: low polarization discrimination,reduced absorption in the detection material, and fabrication complexity. This breakthrough enables the in-situ integration of a 320×256-pixel quantum well infrared photodetector (QWIP) with a chiral metasurface array,overcoming alignment challenges in micro/nano-scale integration. This breakthrough enables the in-situ integration of a 320×256-pixel quantum well infrared photodetector (QWIP) with a chiral metasurface array, paving a new path for developing high-performance circularly polarized depth-of-field partitioned array (DoFPA) detectors for long-wave infrared applications. This achievement was published in the journal “Advanced Science” under the title “Circular Polarimetric Imaging with a Metamaterial Integrated Long-Wavelength Infrared Focal Plane Array.”

Long-wave infrared (LWIR) circularly polarized imaging holds significant applications in circular dichroism spectroscopy, visual defogging, astronomical magnetic field sensing, optical encryption, and biomolecular diagnostics. Traditional circular polarization detection relies on discrete optical components (such as prisms, lenses, polarizers, and waveplates), suffering from issues like bulky size, complex structure, and low temporal resolution. The DoFPA polarimeter achieves compact structure and single-shot imaging capability by directly integrating polarization-selective structures into pixels. However, it faces challenges in the long-wave infrared band, including low polarization extinction ratio, reduced absorption capacity of detection materials, and manufacturing complexity.

The research team employed a chiral metasurface structure to efficiently excite surface plasmon polariton (SPP) modes under the primary circularly polarized incident light while reflecting the other circularly polarized state. Combined with quantum well materials to generate a dual-polarization selection mechanism, this approach achieved a circular polarization extinction ratio (CPER) as high as 23.3. Additionally, the team designed a checkerboard pattern arrangement in the focal plane array. This configuration enables near-in-situ single-exposure detection of the Stokes parameter S3. Although adjacent pixel diffraction and scattering reduced the CPER to 5.67, it still outperforms most integrated infrared circular polarization detectors. This long-wave infrared DoFPA circular polarimeter achieves S3 imaging across the 10-11 μm spectral range with a noise-equivalent S3 difference of 1.16×10⁻⁴, fully meeting high-quality circular polarization imaging requirements. It provides new technical approachesfor realizing more efficient and precise polarization imaging.

Dr. Tianyun Zhu is the first author of the paper. This research was supported by the Chinese Academy of Sciences B-type Pioneer Project, the National Key Research Program of China, the National Natural Science Foundation of China, and the Shanghai Municipal Science and Technology Commission.

Figure 1. LWIR DoFPA circular polarimeter. a) Schematic diagram of the LWIR DoFPA circular polarimeter. One super pixel consists of 1 × 2 pixels, which

are integrated with two chiral meta-mirror structures of opposite chiralities, respectively. b) A photo picture of the LWIR DoFPA circular polarimeter chip

(256 × 320 pixels). c) Schematic diagram of circular polarimetric imaging.

Paper link: https://advanced.onlinelibrary.wiley.com/doi/10.1002/advs.202509292

Contact：Prof. Jing Zhou Email: jzhou@mail.sitp.ac.cn