Heterogeneous-Gradient Supercell Metasurfaces for Independent Complex Amplitude Control over Multiple Diffraction...

The ability to achieve independent complex amplitude control across multiple channels can significantly increase the information capacity of photonic devices. Diffraction inherently holds numerous channels, which are good candidates for dense light manipulation in angular space. However, no convenient method is currently available for attaining this. Here, a flexible interference approach utilizing silicon-based transmission-type heterogeneous-gradient supercell metasurfaces is proposed. By simply designing the phases of the meta-atoms' radiations within a supercell, the complex amplitude of each diffraction channel can be individually and analytically controlled. Crucially, the complex amplitudes of multiple diffraction channels can be simultaneously controlled in a non-interleaved manner, where the number of channels is determined by the number of effective adjusting degrees of freedom (DoF). As a proof-of-concept validation, several meta-devices are experimentally demonstrated in the terahertz regime, which can generate multiple vortex beams, focal points, and splitting beams in different desired diffraction angles. This advancement heralds a new pathway for the development of multifunctional photonic devices with enhanced channel capacity, offering significant potential for both research and practical applications in photonics.