Hosna Sultana, Binbin Weng, University of Oklahoma, Norman, OK
Metasurface is an artificial thin film structure, that offers powerful capability to downsize conventional 3D optics components to 2D flat design, which stimulates new rich photonic engineering areas of manipulating electromagnetic (EM) interaction. This area is boosted by the fast-improving nanofabrication technologies, aiding the subwavelength patterns to manipulate light for optical detection, imaging, and medical technologies becoming more affordable with embedded multifunctionalities. The mid-wavelength infrared (MWIR) spectral range is not only suitable for chemical sensing, and thermal imaging but also for optical communications overcoming the atmospheric loss. So far, the optical detectors for the MWIR range are limited to appropriate materials and sensor operations basis. Flat optics metasurface integration with MWIR detectors could leverage the exploration of the hidden features with high contrast edge detection imaging. In this talk, we propose to explore Germanium-based metasurface for devising polarization-sensitive MWIR detectors. We adopt the single-mode high-contrast metasurface design based on the meta element’s shape, periodicity, aspect ratio, orientation, multiple combinations, and unit cell element number for full phase and transmission control. Assuming the integration with an uncooled focal plane array, this will work as a stoke imager for the 4-micron wavelength. For design optimization, we use the FDTD simulation for implementing asymmetric geometry to minimize the effect of one of the orthogonal phases. This type of design ranges around 2:1 to 4:1 aspect ratio for the Ge meta element on CaF₂ substrate and can yield about 50 percent transmission for each incident polarization state of light with a symmetric 26-degree angular separation in the far field for the two detector positions for separating the incident linearly polarized light or elliptically polarized light. This metasurface integration makes the MWIR detector more sensitive to thermal image recognition with a compact, and affordable price for various agricultural, chemical, and environmental sensing and military applications.