Flexible tuning of multifocal holographic imaging based on electronically controlled metasurfaces

Programmable hyper-coded holography has the advantage of being programmable as well as being flexibly modifiable. Digitally coded metamaterials with excellent electromagnetic modulation capability and the ability to control the phase to modulate the spatial radiation field through external excitation in the form of switching can be used to realize low-cost digital arrays. We design a 1-bit encoded programmable metasurface, which is electrically connected to control the PIN diode in the switching state and to switch the condition of each metasurface cell between “0” and “1.” Using the designed programmable metasurface, we can randomly encode the cell structure to realize single-focus focusing, multi-focusing, and simple holographic letter imaging. Based on the nonlinear holographic model, we employ the Gerchberg-Saxton improvement algorithm to modulate the energy distribution at the focus by adjusting the phase distribution. Importantly, we introduce the Fourier convolution principle to regulate the holographic imaging focus flexibly.