Yijie Shen (Nanyang Technological University) Topological photonic quasiparticles of free space-time

Topological complex electromagnetic waves give access to nontrivial light-matter interactions and provide additional degrees of freedom for information transfer. For instance, topologically stable quasiparticles or skyrmions have been demonstrated in quantum fields, solid-state physics, and magnetic materials, but only recently observed in photonic fields, triggering fast expanding research across different spectral ranges and applications. Here I introduce an extended family of photonic skyrmions within a unified framework, starting from fundamental theories to experimental generation and topological control in spatiotemporally structured light. I will further highlight generalized classes of optical topological quasiparticles beyond skyrmions and outline their exotic topological robust properties, emerging applications, future trends, and open challenges. A complex vectorial field structure of optical quasiparticles with versatile topological characteristics controlled in ultrasmall and ultrafast space-time domain emerges as an important feature in modern spin-orbital optics, imaging and metrology, optical informatics, and topological and quantum technologies.