Conference Agenda

Optical skyrmions can be encoded as spin-textured fields in structured light, where the polarisation varies across the transverse profile of the beam. Their topological properties are characterised by the skyrmion number, an integer-valued topological invariant that groups these field configurations into distinct classes. However their classification typically requires full-field polarimetric reconstruction and subsequent numerical evaluation of the topological invarient. Here, we present a diffractive optical neural network for the direct classification of modes carrying orbital angular momentum (OAM), which are then used to infer the polarity and vorticity of optical skyrmions. Rather than training the network on every possible skyrmionic texture, we train it on the constituent OAM modes in each polarisation channel. The measured modal output then provides the information required to determine the skyrmion number.We discuss how this architecture can be trained in real time using optical feedback from the measured output intensity, enabling hardware-in-the-loop optimisation of the diffractive phase layers. This approach reduces the problem from full-field topological reconstruction to fast, physically interpretable mode classification. By linking OAM detection to skyrmion topology, the platform offers a compact route towards adaptive topological photonic classifiers for structured-light communication, optical information processing, and real-time recognition of complex vector fields.

The broadband THz topological wavepacket is studied and generated via optical rectification through dispersion-engineered polarization control. This THz wavepacket is a superposition of vortices with unique topological structures across the spectrum. The spatial and spectral distributions of the topological wavepacket were measured using full-field THz imaging. The experimental results reveal the frequency-dependent topological transition, including the chirality reversal scalar vortex and cylindrical vortex frequency components. This work establishes a nonlinear route for generating THz topological wavepacket, demonstrates spectral topology in ultrafast THz light springs, and provides a versatile platform for engineering the topological wavepackets by dispersion manipulation.

This paper investigates the 3D polarization dynamics and propagation of Structured Laser Beams (SLB). Generated by optical systems with specific spherical and defocus aberrations, these coaxial beams utilize a "Mexican hat" wavefront to form a self-penetrating wave. This unique architecture enables a transition from a 10 µm source diameter to long-range propagation with an exceptionally low divergence of 10 µrad.

We characterize the internal field structure, fully described by a three-component “vector phase” that represents phase shifts in the transverse and longitudinal directions. A primary contribution is the analysis of illuminating the generator with spatially variant, locally elliptical polarization. We demonstrate, through modeling and experimental validation, that the phase difference and amplitude ratio between radial and azimuthal electric field components are directly mapped onto longitudinal electric (E) and magnetic (B) oscillations within the hollow core. We show that both E and B can be simultaneously longitudinal, with the ability to tune their amplitude ratio and phase difference precisely. In these dark regions, the Poynting vector vanishes due to the dominance of longitudinal components. These results provide a robust framework for applications in high-precision alignment, optical metrology, and a wide range of other fields.

Optical crosstalk between waveguides limits the miniaturization of photonic integrated circuits. Recently, it has been shown that the crosstalk in waveguide arrays can be significantly reduced using higher-order modes, opening a new avenue for decreasing the footprint of photonic chips. Here, we investigate the crosstalk suppression and other peculiar properties of azimuthally polarized higher-order modes by using a semianalytical method for computing the Hamiltonian of the waveguide system. Our findings shed light on the crosstalk suppression mechanism and other discrete diffraction phenomena realizable in waveguide arrays designed to carry higher-order modes.

We report the development of a TD-THz spectroscopic ellipsometry setup to generate and probe vortex beams carrying orbital angular momentum (OAM). Extending structured light to the THz domain opens new opportunities to investigate light–matter interactions beyond the electric dipole approximation. THz vortex beams with tunable OAM and polarization are generated using 3D-printed spiral phase plates (SPPs) or a double-axicon. Full spatial, polarization, and phase-resolved mapping is achieved via time-domain measurements combined with polarization analysis and aperture scanning. Results confirm the ability of the setup to generate vortex beams with controlled OAM and expected properties, enabling future studies of OAM-dependent light–matter interactions in quantum materials.