Structured light for free-space applications

Underwater optical ranging systems face distance limitations due to power loss caused by scattering in turbid water. The authors demonstrate an attenuation-resilient approach using a petal-like structured beam with a tailorable longitudinal intensity profile, which provides a distance-dependent center power gain to ensure accurate ranging in challenging underwater environments.

Intensity-rotating beams are a class of structured beams that can potentially enable advanced optical manipulation techniques, as well as applications in free-space optical communication and high-resolution imaging, but their exploration has remained mostly theoretical. The authors demonstrate galactic-form spinning beams, i.e a stable, intensity-rotating beam whose dynamics and divergence can be precisely controlled.

Vortex-beam-based shift keying secure systems enhance secure digital communications, while it faces challenges such as limited capacity and vulnerability to attacks. This paper presents a double encryption scheme leveraging coherent structures and spatial reading trajectories whichenables key updates without retraining, and maintains high security.

Optical skyrmions, as topologically stable structures, offer promising applications in spintronics and quantum computing, yet their dynamic transitions remain underexplored. Here, the authors demonstrate controllable transitions of two-dimensional optical skyrmions by adjusting Bessel beam components, revealing potential for advanced information processing and transmission technologies.

High dimensional quantum key distribution (QKD) systems will allow for higher key generation rate, but with added complexity for creating and detecting high dimensional quantum states. The authors demonstrate a QKD protocol using “qubit-like” qudit states, “F-qubits”, with simpler generation and detection, maintaining the benefits of high dimensional QKD protocols.

Efficient free-space-to-fiber coupling of cylindrical vector beams (CVBs) is crucial for high-capacity optical communications, yet remains constrained by low coupling efficiency and poor dynamic adaptability in conventional methods. The authors address this issue by introducing a twisted moiré transformation approach that develops ring radius adjustable perfect CVBs using paired meta-devices

Environmental conditions, such as temperature and wind speed, create turbulence that distorts light. Where deciphering the exact origins of any specific optical distort is challenging. In this work, the authors utilize light that twists as it propagates through the air to probe turbulence formation and present a first of its kind optical weather sensor.

High-dimensional quantum key distribution will allow for higher information density and greater error tolerance in future quantum networks. This work experimentally demonstrates how implementing an adaptive optics system in a spatial-mode free-space optical link can allow for quantum communications where it would otherwise be impossible.

Optical beams carrying orbital angular momentum (OAM) are promising candidates for free-space optical communication. The authors devise a hybrid optical-electronic convolutional neural network approach reaching a 4-bit OAM-coded signal demultiplexing accuracy of 72.84% under strong atmospheric turbulence conditions with 3.2 times faster training time than all electronic convolutional neural network.

Photonic integrated processors couple to free-space structured light and on-chip processing reveals its amplitude and phase distribution. The authors demonstrate this concept for higherorder beams, thereby expanding the potential applications of photonic integrated processors.