No abstract

Orbital angular momentum (OAM) multiplexing technology has been developed in the optical information encryption fields. Here, the modulated chiro-optical OAM (MC-OAM) holography is proposed to further improve information security capacity, which integrates the OAM multiplexing technology with the chiro phase modulation. The orthogonality of the axicon parameter, chiro coefficient and rotation angle modulating the chiro phase distributions are analyzed, respectively, which demonstrate their potential usages as extra degrees of freedom besides the topological charge (TC). Those three parameters combining TC serve as four optical keys, which provides a four-dimensional spatial multiplexing method for information security. Furthermore, we have demonstrated that TC minimum interval of the fractional MC-OAM reaches 0.01. The experimental and simulation results exhibit the essential properties in selectivity and multiplexing of MC-OAM holography. This method can significantly increase the holographic information capacity and safety and inspire widespread applications, such as display, information security and communication.

The orbital angular momentum (OAM) owning to the special superiority with the inherent orthogonality, has been identified as an information carrier. In this paper, we proposed a simple and direct method for measurement the OAM of the vortex beam by using vortex grating encrypted OAM holography. When the detected beam illuminates the designed OAM holography, the topological charge (TC)value will be directly read from the reconstruct results which appear as a series of solid Gaussian or ring spots at the output surface of the system. Thus, according to the reconstruct results, we can not only easily detect the modulus but also the sign of the incident beam. Furthermore, it can simultaneously identify OAM modes of multiple incident vortex beams. It's demonstrated that the proposed method is an efficient and flexible method.