The precise generation and manipulation of three-dimensional (3D) vectorial optical fields is essential for emerging applications in volumetric displays, secure data encoding, optical computing, and advanced photonic communication. However, conventional holographic techniques generally lack the capability to simultaneously control both light intensity and polarization within a volumetric region: most methods focus on 3D intensity modulation or two-dimensional (2D) polarization modulation. This constraint prevents conventional systems from reconstructing the complex vectorial light fields increasingly required across modern photonics.
In a new paper published in Light: Science & Applications , a team of scientists from Nanjing University reports a significant advance toward resolving this challenge. They present an ultrathin metasurface able to reconstruct 3D vectorial holograms by engineering the longitudinal evolution of hundreds of structured beams. This approach allows the device to sculpt both the axial intensity and the polarization state of each beam with high precision, enabling genuine volumetric vectorial holography for the first time.
The key innovation is a strategy that decomposes a target 3D light field into a high-density array of quasi non-diffracting beams. Each beam is assigned a tailored longitudinal response function, which quantitatively describes how its intensity and polarization evolve along the propagation axis. These responses are synthesized by superimposing multiple Bessel beam components with uniform spacing in wavevector space. Through careful adjustment of their complex coefficients, the metasurface can generate smooth or abrupt axial intensity patterns, rotating linear polarization, varying ellipticity, and full helicity switching. This grants unprecedented versatility in shaping 3D vectorial light fields.
The metasurface consists of carefully designed rectangular nanopillars of amorphous silicon patterned on a fused silica substrate. Each nanopillar functions as a subwavelength anisotropic scatterer capable of precisely controlling amplitude, phase, and polarization of transmitted light. Through a dual matrix holography framework, the researchers converted the desired vectorial field profile into physically realizable nanopillar geometries and orientations, forming a compact, programmable optical interface only about one millimeter across.
Experimental results show that the metasurface reconstructs sequences of images at well-defined axial depths with high contrast and across a broad range of visible wavelengths. Full Stokes polarimetry confirms that the designed polarization trajectories are accurately reproduced along the propagation direction. The device further demonstrates complex polarization evolution, including trajectories that traverse from one pole of the Poincare sphere to the opposite, validating its ability to create sophisticated 3D vectorial light patterns.
Beyond holography, the researchers demonstrate an all optical encryption scheme uniquely enabled by the platform. Since each symbol is encoded by its depth and polarization signature, information remains hidden within a field of decoy beams unless the correct polarization analyzer and axial position are applied. Without the key, the output pattern appears completely scrambled. With the correct key, the encoded symbols emerge with high contrast. This adds a powerful hardware-level security mechanism that cannot be circumvented through digital analysis or direct inspection of the metasurface.
The authors emphasize that the platform is readily scalable. Increasing the number of superimposed Bessel components or reducing the metasurface pixel size would further enhance axial resolution and enable even richer volumetric scenes. With continuing advances in large-scale metasurface fabrication, this technology holds strong potential for high density optical data storage, secure photonic communication, volumetric display systems, optical steganography, and advanced quantum light engineering.
Light Science & Applications
Longitudinally engineered metasurfaces for 3D vectorial holography