Fig. 1. Working principle and structure of metasurface polarized beam combiner. (a) Working principle of mid-infrared metasurface polarized beam combiner; (b) metasurface structure; (c) three-dimensional structure (left) and top view (right) of the unit cell

Fig. 2. Design principle of metasurface. (a) Reflection phases and (b) reflectivity of X-LP and Y-LP incident light induced by Si nano-antennas with different length L and width W; (c) comparison of the desired phase (Des. X and Des. Y ), the localized cell induced phase (Sim. X and Sim. Y), and the reflectance (Amp. X and Amp. Y) for X-LP and Y-LP incident light at 4.0 μm wavelength

Fig. 3. Simulation results at 4.0 μm wavelength. (a) Normalized far-field intensity distribution and (b) near-field transmission phase distribution of the reflected field when X-LP and Y-LP light incident on the metasurface at 11.54° and -11.54°, respectively; (c) normalized far-field intensity distribution and (d) near-field transmission phase distribution of the reflected field when both of X-LP and Y-LP light incident on the metasurface perpendicularly; (e) normalized far-field intensity distribution of 50 mrad divergence angle at 4.0 μm wavelength

Fig. 4. Simulation results in 3.9-4.1 μm wavelength band. Reflectance of (a) X-LP and Y-LP light within 3.9-4.1 μm wavelength band; (b) normalized far-field intensity distribution and (c) near-field transmission phase distribution of reflected field when X-LP and Y-LP light wavelengths are 3.9 μm and 4.1 μm.

Fig. 5. Transmission performance of the reflected beam. (a) Near filed intensity distribution and (b) phase distribution of reflected X-LP and Y-LP light; spot radii of reflected (c) X-LP and (d) Y-LP light transmitting to different distances

Fig. 6. Performance of polarized beam combining. (a) Variation of beam width with transmission distance after polarized beam combining; (b) comparison of output spectra before and after polarized beam combining