- Sheridan, John T.

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# Sheridan, John T.

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Sheridan, John T.

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Sheridan, John T.

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- PublicationConstraints to solve parallelogram grid problems in 2D non separable linear canonical transform(2017-04-27)
; ; ; ; ; ; The 2D non-separable linear canonical transform (2D-NS-LCT) can model a range of various paraxial optical systems. Digital algorithms to evaluate the 2D-NS-LCTs are important in modeling the light field propagations and also of interest in many digital signal processing applications. In [Zhao 14] we have reported that a given 2D input image with rectangular shape/boundary, in general, results in a parallelogram output sampling grid (generally in an affine coordinates rather than in a Cartesian coordinates) thus limiting the further calculations, e.g. inverse transform. One possible solution is to use the interpolation techniques; however, it reduces the speed and accuracy of the numerical approximations. To alleviate this problem, in this paper, some constraints are derived under which the output samples are located in the Cartesian coordinates. Therefore, no interpolation operation is required and thus the calculation error can be significantly eliminated.287 - PublicationGeneralized model of photopolymer behavior for use in optimized holographic data storage scheduling algorithms(Optical Society of America, 2006-10-10)
; ; ; ; A generalized model of photo-polymerization in free radical chainforming polymers has been developed. Applying this model to data storage, optimized scheduling algorithms are developed for the multiplexing of multiple data pages of uniform diffraction efficiency.245 - PublicationWigner cross-terms in sampled and other periodic signalsIf we sample a scalar wave field, it becomes periodic in frequency. We examine the cross-terms which occur between these periodic replicas in the Wigner-Ville distribution function of such a signal. We present analytic results for Gaussian signals. The results also have implications for physical systems which contain periodic gratings.
290 - PublicationInharmonic theoretical models for photopolymers gratings formation(Optical Society of America, 2005-10-16)
; ; We present an analytical model of the dynamics of spatial harmonics of holographic grating profiles, taking into consideration record mechanisms (polymerization and components diffusion), absorption, interference pattern contrast and optional photopolymerization nonlinearity. On the basis of numerical simulation we compare the model presented with the non-local polymerization driven diffusion model. The results of fitting experimental data with the model results are also presented.208 - PublicationOptical wave propagation simulation, Wigner phase-space diagrams, and wave energy confinement(Optical Society of America, 2005-10-16)
; ; The number of samples required for efficient numerical simulation of wave propagation can be determined by a combination of Wigner phase-space techniques, wave energy confinement arguments, and a theorem relating energy confinement to accuracy.304 - PublicationHolographic grating evolution in photopolymer materials(Optical Society of America, 2007-05-20)
; ; ; ; A generalized non-local polymerization driven diffusion (NPDD) model is presented, including the effects of absorption and inhibition. Experimentally obtained growth curves are fit using a four-harmonic numerical fitting algorithm and key material parameters are extracted.366 - PublicationAn optical encryption scheme that uses polarization of coherent light(Optical Society of America, 2005-10-16)
; ; ; We demonstrate an optical system that encodes two dimensional data as different polarization states. The encrypted image is recorded using a digital holographic setup and the decryption is done numerically.279 - PublicationWavelength-controlled variable-order optical fractional Fourier transformThe relationship between optical fractional Fourier transforms (OFRTs) obtained at different wavelengths is derived by use of the ABCD matrix formalism. It is shown that varying the wavelength while retaining the same optical system can be used to control the order of the OFRT. The advantage of this method of varying OFRT order is that no variation in the characteristics of the bulk optics is required. A general experimental verification of the theory is provided by showing the exact equivalence of two OFRT systems of different order when they are replayed using the same input function at different wavelengths.
274Scopus© Citations 8 - PublicationGeneralization of the boundary diffraction method for volume gratingsThe boundary diffraction method (BDM) is an approximate method that permits the derivation of analytic solutions for the output beams, both forward and backward propagating, that arise from the fundamental nature of holographic gratings. The method is based on the assumption that the volume scatter inside the grating can be supplemented by boundary diffraction coefficients. The boundary diffraction method is used for analysis of thick transmission geometry gratings in a unified way that deals with both the slanted and the unslanted cases. During the analysis, evidence emerges for the superiority of the first-order two-wave beta-value method over the Kogelnik k-vector closure method. The BDM is then further generalized to the case of a volume transmission grating, index matched to its surroundings, and replayed normally on-Bragg, i.e., satisfying the Bragg condition for normal incidence. The analytic equations derived are compared with results calculated with the rigorous coupled-wave method.
263Scopus© Citations 11 - PublicationThickness variation of self-processing acrylamide-based photopolymer and reflection holography(Society of Photo-Optical Instrumentation Engineers, 2001-04)
; ; There are many types of holographic recording material. The acrylamide-based recording material examined here has one significant advantage: it is self-processing. This simplifies the recording process and enables holographic interferometry to be carried out without the need for complex realignment procedures. However, the effect that the polymerization process has on the grating thickness must be examined. This question is fundamental to the material’s use in holographic optical elements, as thickness variations affect the replay conditions of the produced elements. This paper presents a study of this thickness variation and reports for the ﬁrst time the production of reﬂection holographic gratings in this material.469Scopus© Citations 45