We consider the possibilities of information transmission in free space optical communication systems based on encoding with the help of the polarization structure of the synthesized laser beam. To control the polarization structure of beams, an approach based on the fiber array coherent combining with the possibility of changing the direction of subbeam polarization is used. On the basis of numerical simulation, the influence of atmospheric turbulent distortions, as well as the possibility of their adaptive compensation, is analyzed. Situations with different directions of subbeam polarization are considered. It is shown that, for the problems of information transmission, the most stable are the synthesized beams formed at the azimuthal or radial polarization of the subbeams.
The problem of information transmission by modulating the topological charge of the orbital angular momentum (OAM) of beams synthesized by an array of fiber lasers during radiation propagation through a turbulent atmosphere is investigated. The possibility of adaptive compensation for turbulent distortions of a beam in the periodic process of successive phase matching in the receiver plane and phase modulation in the initial radiation plane for information transmission is demonstrated for the first time. A mathematical model of the process of adaptive control for two modifications of the feedback loop and the results of OAM recognition by machine learning methods are presented.
The control over beams with distributed polarization opens new ways for a wide range of applications from optical communications to laser processing of materials. This paper proposes a simple and efficient method of controlling the spatial characteristics of azimuthally polarized beams synthesized as a result of coherent combining of Gaussian beams emitted by a spatially ordered array of fiber lasers. The proposed method is based on maintaining the specified phase relations between the array subbeams by placing a phase forming element - a liquid crystal spatial light modulator - in the active feedback loop. A distinctive feature of the proposed method is the possibility of full control over beams with distributed polarization with phase control of only one component of the electric field. This leads to the significantly simpler design of the experiment. The mathematical model of beam formation and the algorithm of phase control of beams with spatially distributed polarization are discussed. The generation of beams with spatially distributed polarization, including cylindrical vector beams (CVB) and optical vortex beams (OVB), is demonstrated experimentally. The results of the experiment with an array of six fiber lasers are in a good agreement with the results of numerical simulation.
The results of an experiment on formation of a scalar vortex beam in the system of coherent combining of fiber laser beams are reported. Stabilization of phase relations between optical beams is achieved by placing a helicoid phase forming diffraction optical element (DOE) made as a phase plate with helical phase profile in the active feedback loop. Time-stable vortex beams with the topological charge p = ±1 are obtained. The vortex character of the obtained beams is confirmed by the results of interferometric measurements.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.