Terahertz Spin‐Multiplexed Holography Enabled by Photopatterned Large Birefringent Liquid Crystal

ABSTRACT The terahertz (THz) wave manipulation is a key requirement for advanced applications in next‐generation wireless communications, biomedical detection, and high‐resolution imaging. Optical holography is a promising enabling technology to carry out such complicated wavefront control. Compared to the mature techniques in the visible band, counterparts for the THz wave are severely lagging. Here, we propose a spin‐multiplexed and dual‐depth THz holography and demonstrate it in a single photopatterned liquid crystal (LC) device. An improved Gerchberg–Saxton (GS) algorithm is adopted to design the hologram, and random perturbation during the iterative process is introduced to avoid getting trapped in local optimization. The generated diagram is recorded into the alignment of a large birefringent LC with ∆n = 0.45 at 1.0 THz via photopatterning. By reversing the incident circular polarization, “0” and “L” are reconstructed at distances of 6 and 8 mm, respectively. This work validates the feasibility of spin‐multiplexed holography in the THz range and provides a low‐cost and compact solution for 3D THz tomography, anti‐counterfeiting, and information encryption.