Optical communications, laser science, microscopy and metrology demand control of light polarization, which is also used as a probe of chemical and biological systems. Typically, certain polarization states of light are achieved using macroscopic anisotropic crystals. Metamaterials and metasurfaces have recently been developed to act as efficient passive polarization components of subwavelength dimensions^1,2,3,4. However, active polarization control has so far been mainly limited to microwave and terahertz wavelengths^5,6,7. Here, we demonstrate all-optical switching of visible light polarization, achieving up to 60° rotation of the polarization ellipse at picosecond timescales. This is accomplished both under control illumination and in a self-phase modulation regime, where the intensity of light affects its own polarization state, by exploiting the strong anisotropy and nonlinear response of a hyperbolic metamaterial^3,8,9,10. The effects are general for any resonant, anisotropic, nonlinear nanoantennas and metasurfaces and are suited to numerous photonic applications and material characterization techniques where ultrafast polarization shaping is required.

光学通信，激光科学，显微镜和计量学要求对光的偏振进行控制，该偏振也可用作化学和生物系统的探针。通常，使用宏观各向异性晶体可以实现光的某些偏振态。超材料和超表面最近已经发展成为亚波长尺寸^1,2,3,4的有效无源极化组件。但是，到目前为止，主动偏振控制主要限于微波和太赫兹波长^5,6,7。在这里，我们演示了可见光偏振的全光切换，在皮秒级的时间范围内实现了高达60°的偏振椭圆旋转。通过利用双曲线超材料^3,8,9,10的强各向异性和非线性响应，这既可以在控制照明下又可以在自相位调制方案中完成，在该方案中，光的强度会影响其自身的偏振态。这种效应对于任何谐振，各向异性，非线性纳米天线和超表面都是普遍的，并且适用于需要超快极化整形的众多光子应用和材料表征技术。