arXiv subjects

Chengda Song

Publications and source records attributed to Chengda Song.

3 recordsLinked to original sources

arXiv2026

Extreme Energy Concentration of Band-Limited Superoscillatory Vortices for Efficient Optical Micromanipulation

The Abbe diffraction limit, tied to the fundamental spatial bandwidth constraint imposed by any physical aperture, remains the primary barrier to achieving ultimate far-field optical resolution and precise light-matter interactions. However, current efforts to engineer structured light fields beyond this limit often come at the cost of massive sacrifices in energy efficiency. In this work, we mathematically complete the family of non-zero azimuthal-order Circular Prolate Spheroidal Wave Functions (CPSWFs), introducing them as a complete class of band-limited superoscillatory optical vortices carrying helical phase. Compared with classical Laguerre-Gaussian (LG) beams, we rigorously prove that these eigenmodes achieve the theoretical upper bound for extreme energy concentration under strict band-limited constraints. At the scale of light-matter interactions, this optimal concentration directly amplifies the intensity gradients and angular momentum densities that govern optical forces. This advantage translates directly into a 29.9% reduction in the trapping power threshold and a 2.3-fold increase in the subdiffraction orbital rotation speed of nanoparticles. Looking forward, this fundamental physical framework not only establishes strict mathematical boundaries for structured light fields but also serves as an absolute theoretical benchmark for deep-learning inverse design, and next-generation extreme optical micro-manipulation systems.

physics.optics↗

arXiv2025

Subdiffraction confinement and non-diffractive propagation of optical Stokes skyrmions enabled by a super-oscillatory metalens

Optical Stokes skyrmions have garnered extensive interest due to their intrinsic topological robustness and potential in informatics.However, most research remains confined to paraxial, low-numerical-aperture (low-NA) regimes, where their large transverse dimensions restrict broader applications.Under high-NA focusing, the polarization texture typically degrades or transforms abruptly as the beam traverses the focal region, hindering topology-preserving transport.In this work, we propose a strategy to generate a skyrmion needle field that maintains both subdiffraction confinement and non-diffractive propagation under high-NA conditions, thus preserving their topological characteristsics. Leveraging the polarization invariance of conventional optical needles, we realize the Stokes skyrmion needle using a single plasmonic metalens,designed to function as both a polarization filter and a super-resolving focusing element.Experimental and simulation results verify non-diffractive propagation over an extended depth of focus (up to 5 lambda), while the Stokes-vector texture retained at subdiffraction scales throughout propagation. This skyrmion needle not only addresses previous propagation constraints but also opens new avenues for diffraction-unlimited information transport. Such skyrmion needles exhibit substantial potential in fields including light-matter interaction, optical metrology, and informatics.

physics.optics↗

arXiv2025

Generic full-vector angular spectrum method for calculating diffraction of arbitrary electromagnetic fields

Numerous vector angular spectrum methods have been presented to model the vectorial nature of diffractive electromagnetic field, facilitating optical field engineering in polarization-related and high numerical aperture systems. However, balancing accuracy and efficiency in state-of-the-art vector methods is challenging, especially with not well-defined incident fields. Here, we propose a full-vector angular spectrum method for accurate, efficient, robust diffraction computation, allowing truly arbitrary incidence by precisely modeling the projection rule among Cartesian polarization components. We address a prior oversight, that the longitudinal electric field's projection onto the diffracted field was insufficiently considered. Notably, our method inherently handles reflection and transmission at dielectric interfaces, which can be viewed as k-space filters. For rotationally symmetric system, it achieves unprecedented computation times of a few seconds, speeding up optical design via faster input-output mapping in optimization algorithms.

physics.optics↗