Optical Pin Beams Achieve Resilient, Long-Distance Propagation for Free-Space Systems

Optical pin beams represent a significant advance in structured light technology, offering enhanced resilience and long-distance propagation compared to traditional optical beams. Ze Zhang, Hongwei Jiang from China University of Geosciences (Beijing), and Hongyue Xiao from Aerospace Information Technology University and Shandong University, lead a team that comprehensively examines the principles, creation, and potential applications of these unique light fields. The researchers demonstrate how precisely shaping the optical wavefront generates beams with distinctive, pin-like features that exhibit remarkable stability and self-healing capabilities, even when disturbed by atmospheric turbulence. This work, also involving Meiling Guan from Chinese Academy of Sciences, Lu Gao, and Nikolaos K. Efremidis from University of Crete and Institute of Applied and Computational Mathematics, Foundation for Research and Technology-Hellas, highlights the promise of optical pin beams for future innovations in optical communications, precision sensing, and advanced imaging technologies.

This work investigates the fundamental properties of OPBs and explores their potential applications in free-space optical communication and imaging. The research team systematically examines the generation, propagation dynamics, and robustness of OPBs against atmospheric turbulence. Specifically, the study focuses on designing and optimising OPB modes to maximise their on-axis intensity and minimise their sidelobe levels, thereby enhancing signal-to-noise ratios in communication systems., The approach involves utilising advanced beam propagation methods and numerical simulations to model the behaviour of OPBs in various atmospheric conditions.

Researchers develop a novel optimisation algorithm based on a genetic algorithm to tailor the beam parameters for optimal performance. This algorithm considers factors such as beam waist, divergence angle, and wavefront shaping to achieve robust propagation characteristics. The team also investigates the impact of different turbulence models on the beam quality and explores techniques to mitigate turbulence-induced degradation., Key contributions of this work include the demonstration of significantly improved turbulence resilience compared to conventional Gaussian beams, achieving a 2.3-fold increase in the Strehl ratio at a propagation distance of 1000 metres under strong turbulence conditions.

Furthermore, the study introduces a new family of OPB modes with enhanced on-axis intensity and reduced sidelobe levels, resulting in a 1.7-fold improvement in the peak signal-to-noise ratio in a simulated free-space optical communication link. The developed optimisation algorithm provides a versatile tool for designing robust optical beams tailored to specific atmospheric conditions and application requirements, paving the way for more reliable and efficient free-space optical communication and imaging systems.

Tunable Optical Pin Beams Resist Beam Spread

Optical Pin Beams (OPBs) are a class of structured light beams engineered to maintain a tight focus and resist spreading over long distances by precisely controlling the phase and amplitude of the light. Key characteristics of OPBs include reduced beam divergence compared to traditional Gaussian beams, enhanced propagation stability in the presence of atmospheric turbulence or other distortions, and tunable parameters such as beam width, focal length, and polarization for application-specific optimization. Variations of OPBs explored in the research include Vortex Optical Pin Beams (VOPBs) with helical phase fronts, Inverted Optical Pin Beams (IOPBs) with inverted phase profiles, and Vector Optical Pin Beams (VVOPBs) that incorporate polarization control.

A major area of research focuses on Free-Space Optical (FSO) communication, where OPBs are used to improve the reliability and range of long-distance optical links, with successful demonstrations over 1 km outdoor distances. OPBs provide resilience against atmospheric turbulence, resulting in reduced signal fading and improved bit error rates (BER). They also offer higher power efficiency, deliver more optical power to the receiver, and are less sensitive to receiver misalignment or aperture variations. Performance metrics commonly used in these studies include BER, root mean square error (RMSE) of coupled optical power, power fluctuation suppression ratio (PFSR), and eye diagram analysis.

Underwater optical communication is another application area, where OPBs demonstrate advantages in turbulent and particle-laden water environments. Their stability improves BER and error vector magnitude (EVM), providing more reliable underwater links compared to conventional beams.

In imaging applications, OPBs enable hyper-sampling techniques that achieve sub-pixel resolution, enhancing image clarity and detail. These capabilities have been demonstrated with Chinese characters, QR codes, and drone imagery, showcasing the potential for high-precision imaging in complex environments.

The research also explores specific techniques for generating and controlling OPBs. Spatial Light Modulators (SLMs) are used for beam shaping, and plasma structures integrated into optical fibers allow the creation of subwavelength IOPBs. Comparative analyses indicate that OPBs consistently outperform Gaussian beams in stability, signal quality, and propagation range. Their tunability allows optimization for specific environments, while metrics such as scintillation index and beam wander are used to evaluate and mitigate turbulence effects.

Tables and data included in the studies compare performance metrics under various conditions, highlighting the key features and advantages of different structured beams. Overall, the research demonstrates that Optical Pin Beams are a promising technology for enhancing the performance and reliability of optical communication and imaging systems, with ongoing work focusing on parameter optimization, turbulence mitigation, and exploration of new applications in challenging environments.

Airy Beam Arrays Stabilize Light Propagation

This research demonstrates a breakthrough in optical beam propagation, achieving remarkably stable and resilient light transmission through the development of optical pin beams, or OPBs. Scientists constructed these beams by precisely arranging multiple Airy beams, effectively cancelling out transverse wave vectors and compressing the laser beam divergence angle. Simulations reveal that increasing the number of Airy beams from four to 32 significantly optimizes propagation characteristics, with further increases beyond 32 yielding minimal improvement., The team measured a substantial reduction in beam divergence, achieving a Rayleigh length nearly three times greater than that of a conventional Gaussian beam. Analysis of the Poynting vector distribution during propagation revealed a dynamic energy transfer within the beam profile, maintaining beam morphology and fundamentally differing from the outward diffusion observed in Gaussian beams.

This unique characteristic enables stable propagation and disturbance suppression, even in challenging conditions., Experiments and simulations confirm the OPB’s resilience, demonstrating stable wave field maintenance during propagation through turbulence. Notably, the beam exhibits self-healing properties; even with partial obstruction, the beam spot restores its original profile after propagating a certain distance. The research team mathematically describes the system’s dynamics using a Fresnel integral, demonstrating that the initial Airy-type phase, proportional to ρ3/2, is key to achieving stable propagation. These findings pave the way for next-generation optical communication, precision sensing, and advanced imaging technologies.

Optical Pin Beams Resist Turbulence Robustly

Optical pin beams represent a significant advancement in structured light technology, offering robust and stable propagation characteristics for free-space optical systems. Research demonstrates that these beams maintain exceptional collimation and self-reconstructive properties, making them highly resilient to atmospheric and aquatic turbulence, unlike conventional Gaussian beams. Experimental results confirm their effectiveness in diverse applications, including free-space and underwater optical communications, optical trapping, and super-resolution imaging., Investigations into long-distance communication links reveal that OPBs outperform traditional beams in terms of signal stability and bit error rate, even at high data transmission speeds. A receiver-side implementation, reshaping distorted beams into an extended-Rayleigh-length OPB structure, further enhances coupling resilience without requiring complex transmitter-side modulation or adaptive optics. While realizing very long preservation distances necessitates larger transmitting apertures, the inherent turbulence-suppression advantages of OPBs persist within practical ranges, offering superior link stability overall., The authors acknowledge a practical limitation related to aperture size for extremely long distances, however, they highlight the potential for OPBs to transform data center interconnectivity by providing an alternative to fiber optic cables. Future research may focus on optimizing beam parameters and exploring novel applications in challenging environments, solidifying their role in next-generation optical technologies.