Metasurfaces have been rapidly advancing our command over the many degrees of freedom of light; however, so far, they have been mostly limited to manipulating light in free space. Metasurfaces integrated on top of guided-wave photonic systems have been explored to control the scattering of light off-chip with enhanced functionalities—namely, the point-by-point manipulation of amplitude, phase or polarization. However, these efforts have so far been limited to controlling one or two optical degrees of freedom at best, as well as device configurations much more complex compared with conventional grating couplers. Here we introduce leaky-wave metasurfaces, which are based on symmetry-broken photonic crystal slabs that support quasi-bound states in the continuum. This platform has a compact form factor equivalent to the one of grating couplers, but it provides full command over the amplitude, phase and polarization (four optical degrees of freedom) across large apertures. We present devices for phase and amplitude control at a fixed polarization state, and devices controlling all the four optical degrees of freedom for operation at a wavelength of 1.55 μm. Merging the fields of guided and free-space optics through the hybrid nature of quasi-bound states in the continuum, our leaky-wave metasurfaces may find applications in imaging, communications, augmented reality, quantum optics, LIDAR and integrated photonic systems.

超表面一直在迅速推进我们对光的许多自由度的控制；然而，到目前为止，它们大多仅限于在自由空间中操纵光线。已经探索了集成在导波光子系统顶部的超表面，以控制片外光的散射，并具有增强的功能——即逐点控制振幅、相位或偏振。然而，到目前为止，这些努力仅限于控制一个或两个光学自由度，以及与传统光栅耦合器相比更复杂的设备配置。在这里，我们介绍了漏波超曲面，它基于支持连续体中准束缚态的对称性破缺光子晶体板。该平台具有相当于光栅耦合器的紧凑外形，但它提供了对大孔径的振幅、相位和偏振（四个光学自由度）的完全控制。我们展示了在固定偏振态下进行相位和振幅控制的设备，以及控制所有四个光学自由度以在 1.55 μm 波长下工作的设备。通过连续体中准束缚态的混合性质合并引导和自由空间光学领域，我们的漏波超表面可能会在成像、通信、增强现实、量子光学、激光雷达和集成光子系统中找到应用。以及控制所有四个光学自由度以在 1.55 μm 波长下工作的设备。通过连续体中准束缚态的混合性质合并引导和自由空间光学领域，我们的漏波超表面可能会在成像、通信、增强现实、量子光学、激光雷达和集成光子系统中找到应用。以及控制所有四个光学自由度以在 1.55 μm 波长下工作的设备。通过连续体中准束缚态的混合性质合并引导和自由空间光学领域，我们的漏波超表面可能会在成像、通信、增强现实、量子光学、激光雷达和集成光子系统中找到应用。