Ultrafast All‐Optical Polarization Switching Based on Composite Metasurfaces with Gratings and an Epsilon‐Near‐Zero Film

Active control of light polarization is necessary for the development of laser physics, optical communications, and also the molecular dynamics. Conventional polarization control methods suffer from low speed, and the existing all‐optical switching based on nonlinear materials solely has a lot of conducting restrictions, impeding its practical utilizations. Herein, an all‐optical polarization switching in the near‐IR range, composed of the plasmonic gratings deposited on an indium tin oxide (ITO) film with epsilon‐near‐zero response, is realized. A sub‐1 ps response speed and the 19° rotation of the polarization ellipse are determined with the excitation power of 1.37 GW cm−2. The device is demonstrated to output the varied signal with tuning the incident polarization and intensity in a spectral range from 1200 to 1500 nm. The ultrafast processing speed, broadband, and diverse tunability ensure the designed device a promising and necessary element for practically integrating into the next‐generation signal‐processing systems with high performance and large capacity.