Vasu Dev and Yijie Shen of Nanyang Technological University have established a new approach to twistronics by manipulating light fields directly in three-dimensional space. Their work breaks from traditional twistronics which relies on twisted layers of two-dimensional materials, instead creating a “twisted lattice” of propagating light. This freespace twistronics generates previously unreported high-dimensional topologies, including “skyrmionium bags, skyrmion bag superlattices, skyrmion clusters, and optical quasicrystals”. These optical textures maintain their structure over long distances, demonstrating “nondiffractive behavior and robustness” for potential use in robust information transfer and encryption.
Freespace Twistronics Extends Moiré Physics Beyond Materials
The fundamental principle behind this innovation is the superposition of fields, rather than electronic coupling between stacked layers as seen in material-based twistronics. This allows for the creation of higher-dimensional and dynamically reconfigurable geometries that are difficult to achieve with solid-state materials. As the twist angle between the light fields increases, the resulting interference patterns transition from regular lattice structures to more complex, quasiperiodic arrangements, initiating a high-dimensional topological organization in free space.
The researchers explain in their published work. One example detailed in the study is the generation of a C6 skyrmionium lattice beam, where the polarization Stokes vectors form a periodic array of skyrmioniums possessing sixfold rotational symmetry. This tunability is central to freespace twistronics, providing direct optical access to moiré physics and emergent topology without the need for material interfaces. The team’s work allows for the manipulation of moiré photonics with topologies capable of addressing modern challenges in robust information transfer and encryption, offering a new paradigm for optical communication and data security.
“Our work allows for higher dimensions to manipulate moiré photonics with high-capacity topologies,” said Yijie Shen of Nanyang Technological University. The implications of this research extend beyond fundamental physics, offering a pathway to engineer light fields with control and stability.
By moving beyond the limitations of material platforms, freespace twistronics promises a versatile toolkit for manipulating light in ways previously unattainable, potentially impacting fields ranging from optical computing to advanced imaging techniques. The ability to create and maintain these complex optical structures over long distances represents a step towards realizing robust and reconfigurable photonic systems.
Optical Supertopologies: Skyrmionium Bags and Quasicrystals
The creation of stable, three-dimensional light structures with previously unseen topologies is now possible through a new approach to manipulating light, bypassing the need for physical materials. Researchers have demonstrated the generation of complex optical textures, including skyrmionium bags and quasicrystals, that maintain their form over extended distances, a feature not previously achieved in similar systems. These supertopologies, generated by twisting volumes of light, exhibit a robustness against disturbances that promises advancements in areas requiring stable light-based information transfer.
This work establishes a framework for generating a diverse family of optical supertopologies, extending beyond conventional material-based systems. Unlike prior observations of skyrmion bags in liquid crystals or on metal surfaces, these newly created structures exist as freely propagating light fields, eliminating the limitations imposed by a supporting material.
The team’s experiments show long-range distributions of spin textures, confirming the formation of skyrmionium bag superlattices, isolated skyrmionium bags and skyrmion clusters at varying twist angles. The ability to decompose these lattices allows for even more complex structures. This versatility stems from the approach of “freespace twistronics,” which uses twisted moiré interference fields to generate novel topologies. “Many novel topologies, skyrmionium bags, skyrmion-bag superlattices, supertopological quasicrystals, etc., not accessible in any physical system before, now, can be simply generated in twisted bi-volume morié structured light,” the paper states.
The long-range stability and robustness of these optical structures are particularly significant, addressing a key challenge in the field of topological photonics. The team’s findings suggest that these supertopologies could be used to create more reliable and secure methods for transmitting information, as the nondiffractive behavior minimizes signal degradation over distance.
Twisted Optical Lattices Generate Complex Moiré Interference
Moiré structured light, when twisted, can generate topologies previously unseen in optical systems, including complex arrangements of skyrmionium bags, bag superlattices, and optical quasicrystals with controllable symmetry. This expansion of observable structures stems from a new approach to twistronics that moves beyond layered two-dimensional materials and instead manipulates three-dimensional propagating light fields. Researchers have demonstrated the creation of these complex patterns by twisting volumes of topological optical lattices, generating moiré interference fields with novel topologies.
The method relies on the superposition of two structured light fields, each with binary and helical phase distributions and orthogonal polarizations, a technique known as N-wave interference. These lattices, expressed as arrays of discrete point sources in the Fourier domain, are then twisted relative to one another, inducing the moiré effect and resulting in complex, high-dimensional topologies. The stability of these optical moiré textures over long distances represents an advancement over prior moiré superlattices.
These structures exhibit nondiffractive behavior and robustness against perturbations and obstacles, allowing them to maintain their topology during propagation. This is achieved through careful control of the lattice generation process, ensuring high phase stability and accuracy. Experiments with twisted C4 skyrmion lattices at angles of 10.35° and 12.7° for counts of 25 and 13, respectively, yielded geometry-independent skyrmion clusters that maintained their shape during propagation.
Nondiffractive Propagation of Robust Topological Light States
Optical moiré textures generated through this new approach maintain their topological features over extended distances, a characteristic differentiating them from earlier moiré superlattices, and demonstrating a resilience to disruptions during propagation. This long-range stability stems from the fundamental way these supertopologies are created, by twisting light fields from two elementary topological lattices, resulting in interference fields with novel topologies. The resulting light fields exhibit non-diffracting behavior, meaning they maintain their shape and intensity over considerable distances without spreading out, a critical feature for applications requiring precise beam control.
These newly generated supertopologies encompass a range of complex structures, including skyrmionium bags, skyrmion bag superlattices, and topological quasicrystals, all demonstrating this nondiffractive propagation and robustness. To model the intensity of each point source within these lattices, researchers approximated it using a Gaussian distribution, defining coordinates within the Fourier domain to generate the twisted patterns.
Experimental verification of these structures, specifically skyrmion bags, clusters and quasicrystals, was achieved at twist angles of 16.4°, 21.8°, and 27.8°, with measured skyrmion numbers aligning with theoretical predictions. Unit of coordinates for these measurements was millimeters. The stability of these optical lattices extends beyond simple propagation; the structures also demonstrate resilience to obstacles.
While topological protection of skyrmions has been previously studied in complex media, this work demonstrates similar protection within topological lattices even when encountering solid obstructions. “The supertopologies are generated by twisting the light fields of two elementary topological lattices,” the researchers explain, “Therefore, they exhibit the propagation properties of elementary lattices.” This is because a C6 skyrmionium lattice, for example, is composed of only one radial frequency component with six point sources, leading to equal diffraction and propagation invariance within the interference region.
Topological Quasiparticles Enabled by Freespace Twistronics
Freespace twistronics expands the possibilities of moiré engineering by generating optical supertopologies, including skyrmionium bags, skyrmion clusters and topological quasicrystals, that propagate without significant diffraction or loss of stability. These newly observed structures represent a departure from conventional topological light states typically confined to material systems, offering a platform for robust information transfer.
Controlling Topology with Twist Angles in Structured Light
Moiré structured light, manipulated by precise twist angles, now generates optical quasicrystals and skyrmionium bag superlattices, topologies previously unseen in any physical system. Researchers have demonstrated the creation of complex topologies by varying the twist angle between propagating light fields, resulting in both periodic and aperiodic geometries within the moiré patterns. At a twist angle of 13.2 degrees, the resulting optical field forms a superlattice composed of complex skyrmionium bags, each containing multiple elementary skyrmionium clusters surrounded by a larger skyrmionium of opposite polarity.
The outer skyrmionium provides an additional layer of topological protection for the embedded clusters, enhancing their stability. “By varying the twist angle, the lattice topology, and the underlying symmetry, a broad family of nontrivial moiré patterns can be realised,” the researchers state. The ability to create Bloch-type skyrmions and antiskyrmion lattices, alongside the observed skyrmionium bags, expands the range of accessible topological textures.
Extended Data figures illustrate the formation of these textures and their corresponding polarization and skyrmion density maps. These findings demonstrate a resilience to deviations in twist angle; even as long-range order breaks down, the core topology of the central skyrmionium bag remains preserved. This robustness is a key feature of this freespace approach, offering potential for applications requiring stable, long-range propagation of complex light patterns.
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