We propose a double image encryption by using random binary encoding and gyrator transform. Two secret images are first regarded as the real part and imaginary part of complex function. Chaotic map is used for obtaining random binary matrix. The real part and imaginary part of complex function are exchanged under the control of random binary data. An iterative structure composed of the random binary encoding method is designed and employed for enhancing the security of encryption algorithm. The parameters in chaotic map and gyrator transform serve as the keys of this encryption scheme. Some numerical simulations have been made, to demonstrate the performance this algorithm.

We demonstrate that hollow Gaussian beams can be obtained from Fourier transform of the differentials of a Gaussian beam, and thus they can be generated by spatial filtering in the Fourier domain with spatial filters that consist of binomial combinations of even-order Hermite polynomials. A typical $4f$ optical system and a Michelson interferometer type system are proposed to implement the proposed scheme. Numerical results have proved the validity and effectiveness of this method. Furthermore, other polynomial Gaussian beams can also be generated by using this scheme. This approach is simple and may find significant applications in generating the dark hollow beams for nanophotonic technology.

We propose an asymmetric optical image encryption scheme that uses an amplitude and phase mixture retrieval of the Yang–Gu algorithm. The encryption process is realized by employing a cascaded Yang–Gu algorithm together with two random phase masks that serve as the public encryption keys. The two private keys are generated in the encryption process and are randomly distributed binary matrices to be used for performing one-way binary phase modulations. Without the private keys, illegal users cannot retrieve the secret image. Numerical simulations are carried out to demonstrate the validity and security of the proposed scheme.