Metasurfaces are optically thin metamaterials that promise complete control of the wavefront of light but are primarily used to control only the phase of light. Here, we present an approach, simple in concept and in practice, that uses meta-atoms with a varying degree of form birefringence and rotation angles to create high-efficiency dielectric metasurfaces that control both the optical amplitude and phase at one or two frequencies. This opens up applications in computer-generated holography, allowing faithful reproduction of both the phase and amplitude of a target holographic scene without the iterative algorithms required in phase-only holography. We demonstrate all-dielectric metasurface holograms with independent and complete control of the amplitude and phase at up to two optical frequencies simultaneously to generate two- and three-dimensional holographic objects. We show that phase-amplitude metasurfaces enable a few features not attainable in phase-only holography; these include creating artifact-free two-dimensional holographic images, encoding phase and amplitude profiles separately at the object plane, encoding intensity profiles at the metasurface and object planes separately, and controlling the surface textures of three-dimensional holographic objects.

超表面是光学上薄的超材料，可以完全控制光的波前，但主要用于仅控制光的相位。在这里，我们提出一种概念和实践上简单的方法，该方法使用具有不同程度的形式双折射和旋转角度的亚原子来创建可控制一个或两个频率的光振幅和相位的高效介电超表面。这打开了计算机生成全息术中的应用程序，允许忠实地复制目标全息场景的相位和幅度，而无需仅相位全息术所需的迭代算法。我们演示了全介电超表面全息图，具有独立且完全控制的振幅和相位，且同时最多可产生两个光学频率，以生成二维和三维全息对象。我们表明，相振幅超表面能够实现仅相位全息术无法实现的一些功能；这些措施包括创建无伪像的二维全息图像，在物平面分别编码相位和振幅轮廓，在超表面和物平面分别编码强度轮廓以及控制三维全息物体的表面纹理。