On May 15, 2026, a lecture was held in Room 435 of Xingjian Building at the School of Physics Science and Technology, Nanjing Normal University. Academician Xiaocong Yuan of Academia Europaea, Chair Professor at Shenzhen University, was invited to deliver an academic lecture entitled “Singular Optical Field Manipulation and Picoscale Photonics.” The lecture was chaired by Professor Caojin Yuan. Graduate and undergraduate students from related disciplines attended the event.

At the beginning of the lecture, Academician Yuan introduced vortex structures as ubiquitous phenomena in nature, ranging from galactic rotations and black hole dynamics to Earth’s rotation and atmospheric storms. Extending this concept to optics, he explained that light can also form analogous optical vortices, which serve as the foundation of singular optics.

In the theoretical section, Academician Yuan systematically elaborated on two fundamental concepts: the spin angular momentum (SAM) and orbital angular momentum (OAM) of light. Beyond energy and linear momentum, light carries angular momentum: SAM is associated with polarization states, analogous to the Earth’s rotation, while OAM corresponds to the helical phase structure of optical vortices, similar to orbital motion in celestial systems. Together, they constitute the total angular momentum of light. He further highlighted a groundbreaking discovery—the existence of transverse spin angular momentum in evanescent waves, which challenges the conventional understanding that optical spin is strictly aligned with the propagation direction, thereby establishing a crucial theoretical foundation for ultra-precise optical field manipulation.

Subsequently, Academician Yuan presented two major research achievements. In the study of ultrafine optical field structures, his team introduced the concept of skyrmions from magnetism into optics and successfully discovered photonic skyrmions—a unique field configuration in which the spin vectors of photons in evanescent waves form vortex-like distributions. This structure surpasses the optical diffraction limit, reaching deep subwavelength spatial scales. Owing to its ultrafine spin distribution, it enables displacement sensing with picometer-level precision, opening new avenues for ultra-precision metrology.

In terms of technological applications, the lecture highlighted the broad prospects of singular optical fields in optical tweezers and high-speed optical communication. Optical tweezers utilize gradient and scattering forces generated by optical vortices to achieve non-contact manipulation of micro- and nanoscale particles, with important applications in biomedical cell manipulation and micro/nanofabrication. The team’s development of focused surface plasmon polariton (SPP) optical tweezers further enhances manipulation efficiency at the microscale. Meanwhile, optical communication based on OAM multiplexing overcomes the limitations of conventional systems that rely solely on wavelength and polarization, introducing an additional independent channel for information transmission. This significantly increases the capacity of a single communication link while maintaining compatibility with existing technologies, positioning it as a key direction for next-generation high-speed optical communications.

In the latter part of the lecture, Academician Yuan provided a forward-looking overview of the evolution of photonics. From the rise of nanophotonics around 2000 to the rapid development of picoscale photonics in recent years, optical research is advancing from molecular-scale nanometers toward atomic-scale picometers. In terms of spatiotemporal control, time resolution is progressing from femtoseconds to attoseconds, while spatial resolution is extending from the nanoscale to the picoscale, approaching the fundamental limits of matter. In light of the historical trajectory of Nobel Prizes in Physics—awarded to fields such as femtosecond lasers and nano-optics—picoscale photonics is widely regarded as a frontier area with strong Nobel-level potential.

Finally, Academician Yuan introduced a key breakthrough in ultra-precision measurement—the singular optical ruler. Phase singularities in optical fields possess inherently infinitesimal size and extremely large phase gradients, making them ideal natural references for precision metrology. Based on these properties, the team developed a three-dimensional optical ruler and singularity line localization techniques, achieving picometer-scale 3D displacement measurements and ultra-precise object positioning. These advancements have significant implications for applications such as gravitational wave detection, next-generation sub-nanometer lithography, single-atom and single-molecule detection, and quantum information processing.

The lecture was logically structured and content-rich, presenting a comprehensive framework spanning “natural phenomena—fundamental theory—frontier discoveries—technological applications—future perspectives.” The atmosphere was highly engaging, with active discussions between faculty and students. Questions regarding topics such as the controllability of the number of singularities in optical fields and the application prospects of transverse orbital angular momentum were addressed in detail by Academician Yuan, who provided insightful explanations grounded in his extensive research experience.

This lecture not only broadened the academic horizons of faculty and students and strengthened their theoretical foundation in optics, but also inspired enthusiasm for pursuing cutting-edge research and exploring unknown scientific frontiers. It provided a high-level platform for academic exchange at the university.

Speaker Biography:

Xiaocong Yuan is a Chair Professor at Shenzhen University and a Member of Academia Europaea. He is a nationally recognized leading talent and has served as a member of the Discipline Evaluation Group of the Academic Degrees Committee of the State Council (6th, 7th, and 8th terms). He is a Fellow of the Chinese Optical Society (FCOS), Optica (FOSA), the Institute of Physics (FInstP), and SPIE (FSPIE). He serves as Editor-in-Chief of the international journal Advanced Photonics and was awarded the 2026 SPIE Director’s Award. His research focuses on optical field manipulation and its applications. He has published over 600 SCI-indexed papers, including in Science, Nature Physics, Nature Photonics, Nature Communications, Science Advances, PNAS, and Physical Review Letters.