A fully optical encryption system based on the single-phase encryption method is presented. A two-dimensional array of
real-valued data is phase encoded and scrambled with a random phase key for encryption. The encrypted data is stored
holographically in a DuPont photopolymer, and is reconstructed by conjugate readout. The original data can be retrieved
using a same phase key for decryption and an interferometer for phase-to-intensity conversion. The influence of a limited
bandwidth on the bit-error-rate in the decrypted data is evaluated. With binary data, error-free decryption can be possible
even when a large fraction of encrypted data is lost.
An improved image encryption/decryption approach is proposed. In the encryption system, a binary amplitude image is
encoded in the Fourier domain. Then, the encoded image is scrambled with a random binary phase image to produce the
encrypted image. Both the encoding and encryption processes are done electronically. The encrypted image is stored in
an encrypted phase mask of which the transmittance is proportional to the phase components of that image. In the
decryption process, the encrypted phase mask is optically descrambled with another phase mask which has the
transmittance identical to phase components of the random image used in the encryption process. The descrambled field
is inversely Fourier transformed by a Fourier lens in order to reproduce the original image. The simplicity and the
misalignment free characteristics are the most significant advantages of our method. The Fourier encoding process using
an optimization algorithm with iteration technique is discussed in detail. The effect of noise on the quality of the
decrypted image is investigated. The innovation of the system is demonstrated through simulations. The most critical
issue of our technique is that the encryption process requires an optimization search which consumes some computation
time so that the system is expected to be applied for unreal-time applications.
The number of channels of an optical communication system is increasing rapidly. In this paper, the demonstration of a
130-channel demultiplexer based on the cascaded volume holographic gratings is presented. Those gratings are
recorded separately in 100-μm thickness photopolymer films, which attached on both sides of a glass substrate. They
have different grating periods, slant angles, and center wavelengths. By ultilizing this configuration, the operating
wavelength range of the optical demultiplexer could be expanded, and therefore, the number of channels of the
holographic demultiplexer is increased. As a result of the experiment, a 0.4-nm-spaced demultiplexer with the channel
uniformity of 3.5 dB, the 3dB-bandwidth of 0.12 nm, and the channel crosstalk of -20 dB is experimentally achieved.
In this paper, we design a subwavelength binary grating working as a diffractive polarizing beamsplitter. The polarizing beamsplitter is then optimized by using a genetic algorithm to increase its extinction ratios up to as high as 238 and 82. We use the rigorous coupled-wave analysis method to calculate the parameters of the beamsplitter during the optimizing process.
Holographic transmission gratings with 0o;-Bragg angle are widely used to couple light into and out of waveguides due to their high diffraction efficiencies and planar packaging. In this paper, a holographic grating coupler based on the photopolymer has been designed and experimentally demonstrated. To achieve the high diffraction efficiencies, we investigate the optical properties of the coupler according to the exposure energy at the 405 nm wavelength. For the asymmetrical geometry with 72othe correction of the Bragg angles shift of about 0.95o; and 3.45o;, which are induced by the 7.86% shrinkage factor, is successfully demonstrated. The performance and the optical characteristics of the coupler using volume holographic grating are discussed in detail.
A new structure of polarization-selective elements consisting of two holographic gratings and a dove prism coupler is proposed. The absence of a multi-stage wave-guide, compact size, and lightweight volume are the outstanding features of the new structure. Based on the coupled-wave theory, the analysis and design of the structure are discussed in detail to calculate the required index modulation. Several parameters such as the recording intensity, the exposure time, and the recording angles for the fabrication of the proposed element are determined. Under the conditions the element is fabricated in Dupont photopolymer HRF-150-38 material and with the operating wavelength of 532nm. A simplified pick-up head is constructed to evaluate the performance of the fabricated element.
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