A metalens-based optical polarization sensor

An optical microsensor of the laser light polarization state based on a metalens is proposed. Well-known polarization sensors based on metasurfaces usually transmit different types of polarization at different angles to the optical axis. The polarization sensor proposed in this work forms different patterns for different polarization types at the metalens focus. Specifically, the left-handed circular polarization at the focus forms a ring-shaped spot, the right-handed circular polarization – a round focal spot, and linear polarization forms an elliptical spot with two side lobes. Moreover, the angle of inclination of the elliptical focal spot corresponds to the angle of inclination of the initial E-vector of the linearly polarized beam. The simulation is consistent with theoretical predictions. A 30-$\mu m$ metalens with a low aspect ratio, high numerical aperture, and short focal length equal to the incident wavelength 633 nm in a 120-nm thick thin film of amorphous silicon is designed, fabricated and characterized.