The field of subwavelength optics has opened new avenues for investigating light–matter interactions by enabling the exploration of novel phenomena at the subwavelength scale. In recent decades, advancements in fundamental understanding and micro–nano-technologies have significantly propelled the development of subwavelength optics and its practical applications. For instance, progress in surface plasmon subwavelength optics, which facilitates the confinement of light at scales below the diffraction limit, forms a basis for transformative applications such as sub-diffraction-limit imaging, waveguiding and sensing. Moreover, advancements in subwavelength phase manipulation have transcended the constraints of classical Snell’s law on wavefront engineering, leading to the creation of numerous innovative planar/flat optical devices. Furthermore, progress in subwavelength optics allows the integration of optical components onto a single chip, facilitating the miniaturization of optical systems.

This special issue aims to promote the advancement of subwavelength optics by highlighting cutting-edge developments in fundamental theory, core technologies, and engineering applications, encompassing topics such as nonlinear optics, chirality, optical singularities, and functional devices enabled by subwavelength optics.

In this issue, the review article “Nonlinear meta-devices: From plasmonic to dielectric” analyzes the theoretical frameworks of how plasmonic and dielectric materials inducing nonlinear optical properties, and explores plasmonic and dielectric nonlinear meta-devices that can excite strong resonant modes for efficiency enhancement. The researchers also discuss how nonlinear phase manipulation in meta-devices can benefit efficiency enhancement and radiation shaping.

The review titled “Enhancement methods for chiral optical signals by tailoring optical fields and nanostructures” focuses on current chiral optics research. The researchers introduce the theory of chirality and highlight the latest achievements in enhancing chiral signals through artificial nano-structures, with a particular focus on mechanisms such as light scattering and the use of Mie resonance to enhance chiral signals.
The article “Orbit–orbit interaction in spatiotemporal optical vortex” reveals the coupling between the longitudinal orbital angular momentum (OAM) and transverse OAM for the first time. This research demonstrates a new type of orbit–orbit coupling between the longitudinal OAM and the transverse OAM carried by a three-dimensional spatiotemporal optical vortex in the process of tight focusing.

The article “Compound metalens enabling distortion-free imaging” presents a generic approach for on-demand distortion engineering using compound metalenses. The study shows that the extra degrees of freedom afforded by a doublet metasurface architecture allow custom-tailored angle-dependent image height relations and hence distortion control while minimizing other monochromatic aberrations.

The article “Optical singularities in photonic microstructures with rosette symmetries: A unified theoretical scheme” revisits the process of generating optical singularities in microstructures from a symmetry viewpoint. The proposed theoretical scheme reveals that the eigenmodes of a symmetric microstructure can support multiplexed phase singularities in different components. In addition, the researchers demonstrate that the topological invariants associated with optical singularities are protected by the symmetries of the microstructure and formulate a so-called symmetry-matching condition to clarify the excitation of a specific type of optical singularity.

The article “Vectorial digitelligent optics for high-resolution non-line-of-sight imaging” proposes the concept of using vectorial digitelligent optics for high-resolution non-line-of-sight imaging, where the polarization and wavefront of the laser spot are intelligently optimized via a feedback algorithm to form a near-perfect focusing pattern through a random scattering wall. By raster scanning the focusing spot across the object’s surface within the optical-memory-effect range of the wall, nearly diffraction-limited non-line-of-sight imaging with an enhanced signal-to-noise ratio is achieved.

The article “Hybrid-layer data storage with high-orthogonality random meta-channels” proposes the concept of hybrid-layer optical data storage, which can record optical information into a physical layer and multiple virtual layers using high-orthogonality random meta-channels. In the virtual layer, 32 images are experimentally reconstructed through holography, yielding a data capacity of 2.5 Tbit·cm^–3.

The article “A neuro metasurface mode-router for fiber mode demultiplexing and communications” presents a neuro-meta-router optimized through deep learning that achieves spatial multi-mode division and supports multi-channel communication, potentially offering scalability, compatibility, and ultra-compactness. Accordingly, a mode-division multiplexing communication system is theoretically designed and experimentally demonstrated, showcasing a capacity of up to 100 gigabits per second (Gbps) and a symbol error rate down to the order of 10⁻⁴.

The article “Time evolution of orbital angular momentum modes for deep-routing multiplexing channels” introduces a novel approach based on the time evolution of OAM modes. This approach facilitates high-dimensional orthogonal transformations of OAM mode vectors, altering both the propagation direction and the spatial location. Using Fresnel diffraction matrices as unitary operators, it manipulates the spatial locations of light beams during transmission, breaking the propagation invariance and enabling temporal evolution.


Cite this article: Xiangang Luo, Jinghua Teng, Mingbo Pu. Editorial for the Special Issue on Subwavelength Optics. Engineering, 2025, 45(2): 1‒2 https://doi.org/10.1016/j.eng.2025.01.004

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https://www.sciencedirect.com/journal/engineering/vol/45/suppl/C