Reconfigurable Terahertz Holograms with Cascaded Diffractive Optical Elements

This work demonstrates cascaded diffractive optical elements (DOEs) designed through Machine Learning at terahertz frequencies. Machine learning in this application enables the realization of reconfigurable terahertz holograms through a tailored multi-degree-of-freedom variation; that is by either varying the spacing, number, order, and the rotational alignment of the elements it is possible to attain targeted holograms. The designed DOEs are fabricated by 3D printing technique and validated through experimental measurements. In all cases, the desired diffraction patterns are achieved. Such spatial terahertz light control can have a profound impact on terahertz signal multiplexing, displays, and imaging.