The Wireless Laser Communications For Beam (Photon) Based On Orbital Angular Momentum

In recent years,the research for the beam of spiral wave-front that with phase factor exp(ilθ) is a hot topic in the field of optical communication. In this paper, provides an overview of some orbital angular momentum with the beam characteristics and corresponding the size of single-photon orbital angular momentum.Photon orbital angular momentum's probability of detection was influenced on low level atmospheric turbulence aberration within different conditions of atmospheric turbulence, made a optical communications program that apply of single-photon orbital angular momentum states encode. The key technique, system architecture and basis principle of the equipment are demonstrated from the modulation subsystem and demodulation subsystem. This thesis carried through the following aspects of study:1. Design and implement of modulation subsystem.The principle of arising and characteristics of the beam that have the orbital angular momentum were carried out a detailed analysis, chosen the computer-generated hologram to achieve it, for a brief description that the single-photon with orbital angular momentum generated.2. Design and implement of demodulation subsystem. Including the chose of the photoelectric detector that is high sensitivity, beam rotator and composite phase grating for the part of optical signal processing. Also assisted on some devices introduced slightly.3. The working principle of communication systems. From the single-photon orbital angular momentum states have applied to the communication code, the main given is the formula for the course of their work at a glance, Finally, have a brief description for the security of this system.The oretical analysis shows that this system have a high reliability, and compared with the use of polarization encoding,this system can improve the communication capacity. Therefore, the promotion of state encoding with multiple sets of orthogonal single-photon orbital angular momentum is of great significance, it can greatly improve the efficiency of code generated and improve information transfer rate. Finally, the author put forward a summary for the theory of the full text, pointed out the question that to be perfect by the research work in the future.