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A novel approach for producing sidelobe-free optical vortices is proposed, for the first time, utilizing object-oriented computer generated holograms (CGH). By conjugate-symmetrically extending the complex amplitude of any desired optical vortices prior to performing the discrete Fourier transform, the resulting real-valued number profile is encoded into an object-oriented CGH without having conventional forked-shaped fringes. On the basis of the CGH generated, use is first made of numerical simulations to reconstruct optical vortices with spiral phase profiles. Detailed experimental measurements employing a computer-controlled spatial light modulator and extensive numerical simulations are undertaken to verify the proposed technique. Excellent agreements between numerical simulations and experimental measurements are observed. Results show that optical vortices with a single primary intensity ring are generated without the occurrence of any sidelobes in the periphery for absolute values of topological charges as large as 20. [ABSTRACT FROM AUTHOR]

We present a generalized theory for describing encryption and decryption by using the double random phase encoding (DRPE) technique under the framework of the Collins diffraction transform formalism. The theory covers to a variety of diffraction domain which includes the Fourier domain (conventional 4f-optical processor), the Fresnel domain and the fractional Fourier transform (FRFT) domain. From the theoretical basis developed in this work, we present novel optical DRPE systems such as Gaussian imaging DRPE, inverse operation DRPE and Fresnel diffraction DRPE systems, which are plausible to implement. It is shown that the maximum number of degrees of freedom (or independent design parameters) of proposed DRPE system increases four times, when compared with the conventional 4f-optical system, which guarantee much more secure encryption and decryption. [ABSTRACT FROM AUTHOR]