Holographic Encryption Based On Elliptical Optical Vortex

Holography is a technology that uses the principles of interference and diffraction to record and reproduce the light wavefront of an object.It has been used in optical encryption,holographic measurement,three-dimensional display and other fields.Holographic optical encryption uses wavelength,phase,polarization and other optical parameters as coding degrees of freedom to increase capacity,while the orbital angular momentum of an optical vortex theoretically has infinite modes and different modes are orthogonal to each other.In this dissertation,the elliptic optical vortex is combined with holographic encryption,and the generation of high-quality sidelobe-free elliptic optical vortex is studied based on the theory of elliptic optical vortex,and the orbital angular momentum and ellipticity of elliptic optical vortex are used as the encoding freedom to improve the capacity of holographic encryption,dynamic holographic decryption is also realized,the main research contents and achievements are as follows:1.High-quality elliptical optical vortices without side lobes are produced,the relationship between topological charge,ellipticity and elliptic light field distribution is investigated,respectively.Based on the conjugate symmetric continuation Fourier computational holography algorithm,firstly,a high-quality elliptical optical vortex without sidelobes is simulated.Experimental results show that,keeping the ellipticity unchanged,the size of the elliptic light field is proportional to the topological charge.Keeping the topological charge unchanged,when the ellipticity is less than 1,the principal axis of the light field is the y axis;when the ellipticity is greater than 1,the principal axis of the light field is the x axis.Then,an experimental setup was built using spatial light modulator for photoelectric experimental demonstration,and the experimental results were consistent with the theoretical simulation.This study reveals the basic properties of elliptical optical vortices,and provides a theoretical and experimental basis for holographic encryption using elliptical vortex beams.2.The ellipticity encrypted orbital angular momentum multiplexed holography is proposed.Firstly,based on the principle of orbital angular momentum multiplexing,the orbital angular momentum of an optical vortex is used as the encoding degree of freedom,and a 10-dimensional orbital angular momentum multiplexed holography is realized.Then the ellipticity of the elliptic optical vortex is used as the encoding degree of freedom,and the 4-dimensional ellipticity encrypted holography is realized.Finally,both the orbital angular momentum and the ellipticity are used as the coding degrees of freedom,and the 20-dimensional ellipticity encrypted orbital angular momentum multiplexed holography is realized.Experimental results show that the ellipticity of the elliptical optical vortex is used as the coding freedom of holographic encryption,which improves the capacity of holographic encryption.3.Dynamic holographic decryption based on ellipticity multiplexing is realized.Firstly,holographic display and dynamic holographic display are realized.Then,the ellipticity of the elliptic optical vortex is used as the coding degree of freedom of holographic encryption,and the target information is encrypted into different ellipticity channels,and the ellipticity multiplexed hologram is obtained by the iterative algorithm.Finally,the elliptical optical vortices carrying different ellipticities are used as the incident beam,and the dynamic decryption of the target light field is realized.Experimental results show that the dynamic holographic decryption with ellipticity as the coding degree of freedom has better integration,reusability and security.