Fig. 1. (a) Schematic illustration of dual-wavelength (1310 and 1550 nm) imaging polarimetry using the designed metasurface grating. The bottom part shows the experimental image of the detected eight diffraction orders under illumination from 1310 and 1550 nm lights. The incident polarization is randomly chosen. (b) Schematic optimization routine for dual-wavelength (1310 and 1550 nm) polarization metasurface grating design. Unit cell of the dual wavelength metasurface grating, featuring silicon (Si) nanocuboids with an 800 nm height on the silica (SiO₂) substrate. The width (W_x) and length (W_y) vary to enable independent and adjustable phase delays ϕ_x and ϕ_y for x- and y-polarized lights.

Fig. 2. Simulated phase shift ϕx for x-polarized light as a function of the length (W_y) and width (W_x) of the nanocuboid at the wavelength of 1310 (a) and 1550 nm (b). Simulated transmission amplitude |t_x|² for x-polarized light as a function of the length (W_y) and width (W_x) of the nanocuboid at the wavelength of 1310 (c) and 1550 nm (d).

Fig. 3. (a) Optical image of the fabricated metasurface grating sample captured by a 20× microscope. (b) Scanning electron microscope (SEM) images of the fabricated metasurface grating sample.

Fig. 4. Linear polarization detection experimental results of DOP (a) and azimuth (b). Gray lines indicate the theoretical values of DOP and azimuth. Linear polarization detection mean absolute errors of DOP (c) and azimuth (d) at both 1310 nm (green spots) and 1550 nm (red spots). The shaded areas represent the error range (green for 1310 nm, red for 1550 nm).

Fig. 5. Circular polarization detection experimental results of DOP (a), azimuth (b), and ellipticity (c). Gray lines indicate the theoretical values of DOP, azimuth, and ellipticity. Circular polarization detection mean absolute errors of DOP (d), azimuth (e), and ellipticity (f) at both 1310 nm (green spots) and 1550 nm (red spots). The shaded areas indicate the error range, with green indicating 1310 nm and red indicating 1550 nm.

Fig. 6. DOP versus incident linear polarization orientation: theoretical (gray solid lines) and experimental data (green spots for 1310 nm and red spots for 1550 nm). The blue figure depicts the 45° linear polarizer; minimum measured DOP values for 1310 and 1550 nm are 0.024 and 0.055, respectively. The orange figure depicts the 45° linear polarizer; minimum measured DOP values for 1310 and 1550 nm are 0.026 and 0.0018, respectively.