Moussa N’Gom

Recent technological breakthroughs in synchrotron and x-ray free electron laser facilities have revolutionized nanoscale structural and dynamic analyses in condensed matter systems. This review provides a comprehensive overview of the advancements in coherent scattering and diffractive imaging techniques, which are now at the forefront of exploring materials science complexities. These techniques, notably Bragg coherent diffractive imaging and x-ray photon correlation spectroscopy, x-ray magnetic dichroism, and x-ray correlation analysis leverage beam coherence to achieve volumetric three-dimensional imaging at unprecedented sub-nanometer resolutions and explore dynamic phenomena within sub-millisecond timeframes. Such capabilities are critical in understanding and developing advanced materials and technologies. Simultaneously, the emergence of chiral crystals—characterized by their unique absence of standard inversion, mirror, or other roto-inversion symmetries—presents both challenges and opportunities. These materials exhibit distinctive interactions with light, leading to phenomena such as molecular optical activity, chiral photonic waveguides, and valley-specific light emissions, which are pivotal in the burgeoning fields of photonic and spintronic devices. This review elucidates how novel x-ray probes can be leveraged to unravel these properties and their implications for future technological applications. A significant focus of this review is the exploration of new avenues in research, particularly the shift from conventional methods to more innovative approaches in studying these chiral materials. Inspired by structured optical beams, the potential of coherent scattering techniques utilizing twisted x-ray beams is examined. This promising direction not only offers higher spatial resolution but also opens the door to previously unattainable insights in materials science. By contextualizing these advancements within the broader scientific landscape and highlighting their practical applications, this review aims to chart a course for future research in this rapidly evolving field.

Recent advancements in optical wavefront shaping have brought multimode fibers (MMFs) into the spotlight as potential contenders for long-haul communication, positioning them as promising substitutes to single-mode fibers. MMFs offer greater data rates, countering the impending congestion of fiber-based networks. Additionally, their suitability for single fiber endoscope procedures presents them as compelling alternatives for minimally invasive endoscopy, providing information comparable to, if not surpassing, current cutting-edge technology. However, the complex modal behavior of light in MMFs hinders the implementation of these promising applications. Hence, precise modal excitation and control are crucial for improving the transmission of structured light in MMFs. This study introduces a groundbreaking approach that achieves the retrieval of the transmission matrix in a single step, thereby facilitating coherent light propagation through highly dispersive MMFs. By combining iterative phase retrieval algorithms with the measurement of phase shifts between experimentally established focal points, potential arbitrary interference control is enabled, leading to effective phase correction. The efficacy of our method is validated through the successful transmission of diverse structured light beams, including Laguerre–Gauss and Hermite–Gaussian types, as well as handwritten characters via MMF. The examination of structured light is simplified using an off-axis holographic technique that accurately captures both intensity and phase information. These results hold significant potential, paving the way for major advancements in long-distance communication and minimally invasive medical procedures, thereby transforming the telecommunications and healthcare sectors.