Orbital angular momentum channel healing using a Fabry-Pérot cavity 

Orbital angular momentum (OAM) in optical vortex beams offers a new degree of freedom to increase the capacity of free-space optical communication systems, breaking the limitation of conventional multiplexing methods. In the OAM-based optical communication system, OAM can be regarded as information carriers for OAM division multiplexing (OAM-DM). However, the practical deployment of OAM within a free-space optical (FSO) communications system is still hampered by a major challenge, namely that OAM-based FSO links are vulnerable to disturbances. Our work provided a simple but powerful strategy to heal a broken OAM beams by using a high-q Fabry-Pérot (FP) resonant cavity. Different OAM states will resonant in the FP cavity by simply charging the cavity lengths. Through fixing the resonating cavity length for a particular OAM state, the OAM beam will propagate in the cavity hundreds of times. A broken OAM beam could be healed when it resonates in the cavity even with the blocking percentage of over 50%. This technique will expand the use of OAM in the FSO secure communications and quantum encryption fields.

    Prof. Xiaocong Yuan and Prof. Jiao Lin, who are from Nano Photonics Research Centre (Shenzhen University), propose a simple but powerful technique to heal broken OAM channels, which will obviously increase the stability of OAM division multiplexing (OAM-DM) in optical communication system. Optical communications in both free-space optical (FSO) and fiber optic technologies have achieved dramatic increments in their aggregate transmission rates using multiplexing/demultiplexing (MUX/DEMUX) technologies. OAM beams have helical phase profiles in their electric fields that are proportional to the azimuthal phase term, also known as topological charges. In principle, the topological charges  which makes OAM beams are good information channels are unlimited to carry signals for data transmission. Despite free-space optical (FSO) communications systems that use OAM encoding/multiplexing technology having numerous advantages over conventional systems, such as low cost, license-free, high bandwidth, and terabit-scale in a laboratory environment, the widespread use of such systems still faces obstacles in complexes environments. In an open environment, intensity fluctuations caused by obstacles are introduced and become intractable challenges for FSO communications, bringing about a degradation of the systems' capacities. This new technique provides a solution to increasing the system stability when it works in the complexes environments of many unexpected obstacles. A simple commerical FP cavity configuration is easy to integrate. It is a promising technique for the practical FSO communication system.

 

About Team
Nano Photonics Research Centre (Shenzhen University) led by Professor Yuan Xiaocong, founded in 2013, aims to create a micro nano optical includes basic research, functional device preparation, evaluation and application of innovative research platform, committed to the research of super-resolution imaging and super sensitivity, the orbital angular momentum of optical communication and optical interconnection, optical micro and nano photonic processing and photoelectric devices etc.. Research team currently has 9 teachers, including 1 scholars of the Yangtze River, 2 National Outstanding Youth Fund, the Ministry of education in the new century outstanding talent 1, Shenzhen peacock plan talent 5. Now assume all kinds of a total of 30 projects, including 16 national projects, provincial and municipal projects in 14, including the National Fund Committee of major scientific instrument development projects in 1, the National Science Foundation major project 1, national 973 project 1, the National Science Foundation's 1 key projects, the National Outstanding Youth Fund Committee project 2, Shenzhen city launched 4 projects of scientific research personnel peacock, the total research funding more than 60 million yuan. Research team at all levels of the strong support of the leadership of the Shenzhen University, has made considerable development, has absorbed 11 postdoctoral, doctoral graduate 9, master's degree 33.

 

Article

Wei S B, Wang D P, Lin J, Yuan X C. Demonstration of orbital angular momentum channel healing using a Fabry-Pérot cavityOpto-Electronic Advances 1, 180006 (2018).
DOI:10.29026/oea.2018.180006