Numerical optimization of writing computer-generated holograms in threshold media

Recent developments in binary photo-magnetic materials showed efficient and ultra-fast rewriting of holograms where the intensity threshold allows for a dense, sub-diffraction limit packing of hologram points. This paper describes the numerical optimization of the process of writing and reconstructing of 2-D images in a binary-phase computer-generated holograms stored in the said threshold-like medium. Global optimization of the free parameters of the writing process is shown, including the intensity threshold level, propagation distance, hologram spot size and the shape of the boundary regions of the written spots. We present the optimal set of parameters for the best possible writing quality. Full Text: PDF ReferencesA. Stupakiewicz, K. Szerenos, D. Afanasiev et al., "Ultrafast nonthermal photo-magnetic recording in a transparent medium", Nature 542, 71 (2017). CrossRef J. Starobrat, A. Frej, J. Bolek, R. Trybus, A. Stupakiewicz, and M. Makowski, "Photo-magnetic recording of randomized holographic diffraction patterns in a transparent medium", Opt. Lett. 45, 5177 (2020). CrossRef V. Ostroverkhov, et al., "Micro-Holographic Storage and Threshold Holographic Recording Materials", Jap. J. App. Phys. 48.3S1, 03A035 (2009). CrossRef K. Matsushima, T. Shimobaba, "Band-Limited Angular Spectrum Method for Numerical Simulation of Free-Space Propagation in Far and Near Fields", Opt. Express 17, 19662 (2009). CrossRef F. Wyrowski, O. Bryngdahl, "Iterative Fourier-transform algorithm applied to computer holography", JOSA A 5.7, 1058 (1988). CrossRef I. Ducin, T. Shimobaba, M. Makowski, K. Kakarenko, A. Kowalczyk, Jaroslaw Suszek, M. Bieda, A. Kolodziejczyk, M. Sypek, "Holographic projection of images with step-less zoom and noise suppression by pixel separation", Opt. Comm. 340, 131 (2015). CrossRef M. Makowski, "Minimized speckle noise in lens-less holographic projection by pixel separation", Opt. Express 21, 29205 (2013). CrossRef

Angle-Multiplexing Nonlinear Holography for Controllable Generations of Second-Harmonic Structured Light Beams

Nonlinear multiplexing holography emerges as a powerful tool to produce structured lights at new wavelengths. In this work, we propose and experimentally demonstrate an angle-multiplexing nonlinear holography in an angular noncritical phase-matching configuration. In experiment, various types of structured light beams, such as vortex beam, Airy beam and Airy vortex beam, are simultaneously output at second-harmonic waves along different paths. Because of the large angular acceptance bandwidth of noncritical phase-matching, one can achieve high conversion efficiency of angle-multiplexing nonlinear holography. Our method has potentially applications in high-capacity holographic storage and security encryption.

Scenario of accelerated universe expansion under exposure to entropic forces related to with the entropies of Barrow and Tsallis−Cirto

In the work within the framework of "entropic cosmology", the scenario of the cosmological accelerated expansion of a flat, homogeneous and isotropic Universe under the influence of entropic forces is considered without the concept of dark energy a hypothetical medium with negative pressure. Assuming that the horizon of the Universe has its own temperature and entropy, which arises during the holographic storage of information on the screen of the horizon surface, the entropy models of the Universe associated with the BekensteinHawking entropy and the non-extensive Barrow and Tsallis–Cirto entropies are considered. The modified equations of acceleration and continuity of Friedman with governing power terms having an entropic nature are derived both within the framework of Einstein's general theory of relativity and on the basis of a thermodynamic approach that allows modeling the non-adiabatic evolution of the Universe. At the same time, models based on nonextensive entropies predict the existence of both a decelerating and accelerating Universe.

A Facile Fabrication Route of Poly(Ethylene Glycol Phenyl Ether Acrylate) Photopolymers with Efficient Optical Response for Holographic Storage

A series of photopolymers based on ethylene glycol phenyl ethyl arylate (EGPEA) monomers and poly(methyl methacrylate) (PMMA) matrix with varying initiator concentrations and sample thicknesses have been synthesized and their optical performance characterized in this study. The advantages of lowering the initiator concentration, including a rather short initiation time within a few seconds; a sharp rising optical response; and a stable saturated diffraction efficiency are demonstrated. The variation in the diffraction efficiency and response time with the exposure energy under various sample thickness and initiator concentrations is examined; a diffraction efficiency as high as 80% and a relatively short response time of 12–39 s are attainable. The dependence of the normalized optical parameter “sensitivity” on the exposure time is depicted, and the peak value of S ranges vastly from about 0.2 to 1.2 × 104 cm/J within a period of 15 s or so, with a maximum value of nearly 1.2 × 104. Favorable evidence of low initiator concentration can further be found when the dependence of the saturated diffraction efficiency with the exposure energy is examined. The data from this study using a low initiator concentration cover a range of exposure energy from 100 to 800 mJ/cm2 and a saturated diffraction efficiency from about 15% to 80%. The successful image reconstruction of 6-membered-ring metal nuts on a hologram based on this EGPEA/PMMA photopolymer system using a reflective holographic recording setup is demonstrated to verify its applicability to holographic storage.