Topological complex electromagnetic waves give access to nontrivial light-matter interactions and provide additional degrees of freedom for information transfer. An important example of such electromagnetic excitations are space-time non-separable single-cycle pulses of toroidal topology. Here we introduce an extended family of super-toroidal electromagnetic excitation, which exhibit skyrmionic structure of the electromagnetic fields, multiple singularities, and fractal-like energy backflow. By further introducing bandlimited effect into super-toroidal pulses, we show that space-time non-separable band-limited light fields can exhibit superoscillations simultaneously in the spatial and temporal domains, i.e. can oscillate faster that the highest harmonics of their spectra. The super-toroidal pulses with space-time superoscillation are of interest for transient light-matter interactions, ultrafast optics, spectroscopy, and toroidal electrodynamics.
Structured light fields embody strong spatial variations of polarization, phase, and amplitude. Understanding, characterization, and exploitation of such fields can be achieved through their topological properties. Three-dimensional (3D) topological solitons, such as hopfions, are 3D localized continuous field configurations with nontrivial particle-like structures that exhibit a host of important topologically protected properties. Here, we propose and demonstrate photonic counterparts of hopfions with exact characteristics of Hopf fibration, Hopf index, and Hopf mapping from real-space vector beams to homotopic hyperspheres representing polarization states. We experimentally generate photonic hopfions with on-demand high-order Hopf indices and independently controlled topological textures, including Néel-, Bloch-, and antiskyrmionic types. We also demonstrate a robust free-space transport of photonic hopfions, thus showing the potential of hopfions for developing optical topological informatics and communications.
Topological complex electromagnetic waves give access to nontrivial light-matter interactions and provide additional degrees of freedom for information transfer. An important example of such electromagnetic excitations are space-time non-separable single-cycle pulses of toroidal topology. Here we introduce an extended family of super-toroidal electromagnetic excitation, which exhibit skyrmionic structure of the electromagnetic fields, multiple singularities, and fractal-like energy backflow. By further introducing bandlimited effect into super-toroidal pulses, we show that spacetime non-separable band-limited light fields can exhibit superoscillations simultaneously in the spatial and temporal domains, i.e. can oscillate faster that the highest harmonics of their spectra. The super-toroidal pulses with space-time superoscillation are of interest for transient light-matter interactions, ultrafast optics, spectroscopy, and toroidal electrodynamics.
The ray-wave geometric beams (RWGBs) are fantastic structured light field with multiple degrees of freedom (DoFs). These DoFs endow countless application prospects for RWGBs in optical communication, quantum entanglement, optical tweezers. Meantime, the intricate orbital angular momentum (OAM) structures and intensity shape brought by these DoFs have caused great difficulty in its sort and limited its application. We propose a new digital holographic method to identify multi-DoFs RWGBs based on the conjugated modulation theory, thus called conjugated modulation identification (CMI). The experiment results indicate that the RWGBs were fully resolved, and the reconstructed correlation degree shows good agreement with the theoretical values. Furthermore, the 8-bit and 16-bit multi-RWGBs shift keying encoding were demonstrated. The signal is well recovered with no error, demonstrating the proposed method with good data transmission performance. Our work reveals wide potential applications of RWGBs in realizing high-speed, high-dimensional time-varying modes multiplexed encoding and high-capacity multi-channel communication..
Structured light with diverse degrees of freedom (DoFs) has recently attracted wide attention. Especially, the ray-wave beams that could be described by both rays and wave packet, can open multiple DoFs by the ray- wave duality. Here a generalized ray-wave beam family is proposed to unify the spatial mode evolution of the azimuthally traveling-wave (TW) and standing-wave (SW) structured light, by introducing a reconfigureable ray-split/fusion structure. We derive an elegant closed-form expression by utilizing frequency-degenerate Ince- Gaussian eigenmodes to construct a new ray-wave beams family to precisely parameterize the ray-split/fusion process, pushing structured light control in higher dimensions. We also experimentally generate these modes by dynamic control of a digital hologram system, revealing their potential applications in optical manipulation and communication.
Toroidal light pulses are few-cycle pulses with doughnut-like electromagnetic field configuration and non-separable, “entangled”-like spatiotemporal structure. Toroidal light pulses exhibit self-similar and skyrmionic topological features and exotic propagation dynamics including isodiffracting and non-diffracting effects. Following the recent observation of such pulses, this talk will report on metamaterial-based schemes for their generation and detection and introduce tomography approaches for characterizing their “entangled” spatiotemporal profile. Implications for light-matter interactions, in particular in the context of toroidal electrodynamics, non-radiating configurations, and Lorentz non-reciprocity, will also be discussed.
Structured light, with ability to arbitrarily tailor degrees of freedom (DoFs) of light, amplitude, phase, wavelength, etc, has recently attracted great promotion for fundamental science and advanced applications. In addition to the basic DoFs in light, there are also some complex DoFs emerged as the combination of common DoFs, such as angular momentum, vector singularity, ray-wave trajectory, spatiotemporal vortex, etc., showing their power in optical manipulation. In this talk, I summarize the advanced methods of manipulating tunable DoFs and creating new DoFs in structured light, as a roadmap guiding the development of multi-dimensional structured light. We also discuss the significance of the multi- DoF control in both fundamental physics and novel applications.
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