Search Results (183)

To address the key issues of uneven distribution of functional groups, large dispersion of holographic storage performance across different regions, and poor consistency of storage capacity in traditional PQ/PMMA holographic storage photopolymers, this paper introduces a low-viscosity reactive diluent, tripropylene glycol diacrylate (TPGDA), to modify the matrix. Leveraging the viscosity-reducing and double-bond crosslinking properties of TPGDA, the molecular diffusion behavior of the system was regulated. The effects of TPGDA doping ratio, the ratio of photosensitizer PQ to thermal initiator AIBN, and post-curing process on the holographic performance uniformity of the material were systematically investigated. The uniformity was quantitatively evaluated by the variance of diffraction efficiency at different points. Visible light absorption spectra and Fourier-transform infrared (FT-IR) spectroscopy were employed to reveal the modification mechanism from the perspective of functional group distribution. Actual-data read/write tests were conducted using a collinear holographic storage system. The experimental results show that the optimal TPGDA doping concentration is 40 wt%. For the optimized formulation TPGDA:MMA:AIBN:PQ = 8 g:12 g:0.20 g:0.18 g, the modified material achieves an average diffraction efficiency of 76.58%, and the diffraction efficiency variance decreases from 23.49 (pristine matrix) to 1.64, indicating a significant improvement in performance uniformity. Compared with pure PQ/PMMA, the modified material exhibits an approximately 1.95-fold increase in maximum diffraction efficiency, a 2-fold increase in recording rate, and a 1.6–1.75-fold increase in refractive index modulation. FT-IR spectroscopy confirms that TPGDA optimizes the spatial distribution uniformity of C=C and C=O functional groups. In collinear holographic measurements, the bit error rate (BER) variance of the modified sample is reduced by 40% relative to the pristine matrix, achieving homogeneous storage performance across the entire area while maintaining comparable signal-to-noise ratio (SNR) and BER. Additional short-time UV post-curing can further enhance the diffraction efficiency and refractive index modulation, and a thinner substrate can avoid performance fluctuations caused by incomplete thermal curing of thick samples. This study achieves directional optimization of the holographic uniformity of PQ/PMMA through reactive diluent viscosity reduction modification, providing a new strategy for the formulation design and engineering preparation of high-consistency holographic storage photopolymers. Full article

In this study, we employed one of the green synthesis methods utilizing water extracts prepared from solid industrial wastes of Rosa damascena Mill. (RD) and Oriental variety tobacco (Nicotiana tabacum)-mixed stems and leaves (O) as a natural reducing agent for PdCl₂ to obtain environmentally friendly Pd nanoparticles (PdNPs). Transmission electron microscopy (TEM), selected area electron diffraction (SAED), and energy-dispersive X-ray spectroscopy (EDX) in TEM were applied to determine the morphology, microstructure, phase, and elemental composition of PdNPs synthesized. The concentration of PdNPs in the suspensions was quantified by inductively coupled plasma optical emission spectroscopy (ICP-OES), which is essential for their intended application. Furthermore, the synthesized PdNPs were incorporated as dopant into a polymer matrix (PAZO) developed for optical applications. As will be demonstrated, doping PAZO with specific concentrations (0.1, 0.2, 0.25, 0.3, 0.4, 0.5, and 1 wt. %) of green PdNPs enhances the maximal value of the photoinduced birefringence by more than 50%. This improvement enables more efficient inscription of polarization-selective holographic optical elements in the resulting photoanisotropic nanocomposite materials with nearly 25% higher diffraction efficiency. Using a digital polarization holographic setup, the spatial modulation of polarization was recorded on thin nanocomposite films of the azopolymer PAZO, doped with certain concentrations of the green PdNPs. Full article

Accurate axial localization of microparticles is a key requirement in in-line digital holography (ILDH), particularly under noisy conditions and for weakly scattered objects. This work presents experimental and simulated benchmarking of three widely used focus metrics: maximum intensity, complex amplitude, and Kurtosis. Experimental holograms of microparticles with different diameters were recorded using a compact ILDH system, while simulated holograms of a 10 µm particle were generated. Numerical reconstruction was performed using a Fresnel convolution approach with FFT-based propagation over a range of axial distances. The performance of each focus metric was evaluated based on peak definition, robustness to coherent noise, and consistency across particle sizes and configurations. The results show that both maximum intensity and Kurtosis provide consistent and reliable axial localization, with very similar behavior across all cases. In contrast, the complex amplitude metric is more sensitive to noise and exhibits larger fluctuations in the axial response. These results indicate that simple intensity-based metrics can achieve accurate localization under moderate signal-to-noise conditions, while higher-order statistical metrics improve robustness in more challenging scenarios. This work provides practical guidelines for selecting autofocus criteria in ILDH systems for particle imaging and holographic metrology. Full article

Volume phase holographic gratings (VPHGs) are high-performance dispersive elements characterized by high diffraction efficiency and low noise. When used as dispersive components in imaging spectrometers for CO₂ detection, they can significantly enhance instrument performance, detection capability, and measurement accuracy. However, for short-wave infrared (SWIR) applications requiring high dispersion and operational efficiency, traditional design approaches struggle to effectively balance the trade-offs among multidimensional diffraction performance metrics, resulting in low optimization efficiency. Furthermore, as spectrometers require dispersive elements, established fabrication methods lack robust methodologies for producing large-area VPHGs. To address these gaps, we developed both a design approach and a fabrication process for VPH gratings tailored to CO₂ detection. On the design front, we propose a novel method that integrates a multi-objective simulated annealing optimization algorithm with Kogelnik’s coupled-wave theory. The optimized gratings achieve diffraction efficiencies of 95.35% (TE polarization) and 82.21% (TM polarization) across the target spectral range, with polarization sensitivity maintained below 6.57%. For fabrication, we developed holographic plate fabrication via a blade-coating technique coupled with an optimized aging protocol. A medium-to-large aperture holographic recording and exposure system with a wavefront error better than λ/25 RMS was developed. Post-processing conditions were systematically optimized based on experimental diffraction efficiency measurements, enabling the successful fabrication of VPHGs. It is explicitly noted that the experimental validation of the fabricated VPHGs is limited to the 1.620–1.630 μm wavelength range, while the full target design range of 1.620–1.650 μm has not been experimentally verified in this work. This work provides a valuable reference for the selection of dispersive elements for next-generation CO₂ detection satellites. The designed gratings fully meet application requirements, while the established fabrication process lays a solid foundation for the production of high-performance VPHGs. Full article

Lensless digital holography provides a simple, low-cost imaging platform with a large field of view (FOV) and quantitative phase capability, making it attractive for biomedical imaging, microstructure inspection, and large area imaging. However, the achievable FOV is still limited by sensor size, and in-line reconstruction suffers from twin-image artifacts that degrade image quality. To overcome these limitations, this study proposes an extended FOV lensless digital holography method that combines hologram stitching with multi-depth phase retrieval. Multiple holograms acquired from laterally shifted FOVs are stitched to form an extended hologram, while holograms recorded at multiple axial depths are used to suppress twin-image artifacts and improve reconstruction fidelity. Experimental results show that the proposed method effectively expands the imaging area, enhances effective resolution by integrating complementary diffraction information from different FOVs, and improves image contrast and feature visibility. This approach enables extended FOV, resolution enhancement, and high-quality holographic imaging while preserving the simple lensless digital holography architecture. Full article

A collinear holographic data storage system stores two-dimensional information in the three-dimensional spatial domain of the medium, offering features such as high speed, high density, and long lifespan, making it a promising technology for the future of data storage. However, a collinear holographic data storage system is limited by the alignment error of the optical system and is also sensitive to environmental noise and external interference, which increases the reading error. When recording and reading holographic storage materials, synchronous marks are used for positioning to correct data misalignment. Therefore, optimizing synchronous mark design of data pages is crucial for improving storage stability and reading accuracy. In this paper, we propose a star-shaped synchronous mark to replace the square-shaped synchronous mark, which improves the holographic grating coupling efficiency. Experimental results show that this method enhances reconstruction strength and reduces reading errors caused by external factors. The star-shaped synchronous mark achieves a better spectral match with the reference pattern, yielding a stronger diffracted signal. Experimental results show that this method reduces the bit error rate by approximately 25% compared to square-shaped synchronous marks under displacement multiplexing. Full article

Mixed-scene holographic 3D display for film and television visual content presentation remains challenging because recorded digital holograms and computer-generated holograms (CGHs) are produced under different numerical and hardware constraints. Direct hologram superposition typically causes strong zero-order interference, diffraction efficiency degradation, and sampling pitch mismatch between the recording sensor and the replay panel, while conventional resizing reduces the effective replay aperture and narrows the available parallax. To address these issues, this paper proposes a zero-order-suppressed single-hologram fusion framework with parallax-preserving digital resizing. A recorded digital hologram is first processed by Gaussian high-pass filtering to suppress the dominant zero-order component, then resampled to match the LCOS replay pitch, and finally normalized and fused with a CGH generated through bipolar intensity encoding. On this basis, two resizing routes are developed: a spatial-domain method for aperture-preserving whole-scene scaling and a frequency-domain method for object-selective scaling and translation. Optical validation on a three-channel LCOS prototype shows that the quantitative diffraction efficiency analysis predicts an increase from approximately 10.1% to 20.05% per reconstructed object for the two-hologram fusion case, and the revised experimental results are consistent with this improvement trend. The experiments further verify replay scaling at multiple factors, the selective manipulation of physical and virtual objects, mixed-scene color replay, and occlusion-consistent depth ordering. Together with the distortion analysis, these results demonstrate improved replay visibility after fusion while maintaining geometric controllability and effective replay aperture. By relying on hologram-domain preprocessing and resizing rather than full mixed-scene recomputation, the proposed method also reduces computational burden. The study therefore provides an efficient and controllable mixed-scene holographic replay framework for visually enriched film and television content presentation, although its depth applicability remains bounded and dedicated real-time timing benchmarks are left for future work. Full article

With the advent of the big data era, traditional storage technologies struggle to meet the demands for long-term, secure, and cost-effective preservation of massive amounts of information. Collinear holographic storage technology has emerged as a strong contender for next-generation optical storage due to its high storage density, rapid parallel transmission, and exceptional reliability. Among various storage materials, phenanthraquinone-doped poly(methyl methacrylate) (PQ/PMMA) photopolymer has garnered significant attention for its negligible photo-induced volume shrinkage, low cost, controllable thickness, and polarization-sensitive holographic response properties. However, the material’s limited photosensitivity, low polarization response, and poor optical uniformity severely constrain its application in high-speed recording and multidimensional multiplexing holographic systems. This paper reviews the primary methods and strategies employed over the past five years to enhance the holographic performance of PQ/PMMA photopolymer materials, based on the microscopic physicochemical mechanisms underlying traditional and polarization holography, including chemical modification, nanoscale doping, mechanical control, etc. Through a systematic review of these research advances, this paper aims to provide theoretical foundations and technical references for developing high-performance PQ/PMMA photopolymer materials suitable for collinear holographic storage. Full article

We propose a field-transformation-based framework for generating phase-only light-field holograms from a single RGB image. The method establishes an explicit pipeline from monocular scene inference to holographic wavefront synthesis, without requiring multi-view capture or task-specific hologram-network training. First, we construct a layered occlusion RGB-D model from the input image using monocular depth estimation, connectivity-based layer decomposition, and occlusion-aware inpainting, which provides a lightweight 3D prior for sparse-view rendering in the small-parallax regime. Second, we transform the rendered sparse RGB-D light field into a target complex wavefront on the recording plane through local frequency mapping, thereby bridging explicit scene geometry and wave-optical field construction. Third, we optimize the phase-only hologram under multi-plane amplitude constraints using a geometrically consistent initial phase and an error-driven adaptive depth-sampling strategy, which improves convergence stability and reconstruction quality under a limited computational budget. Numerical experiments show that the proposed method achieves better depth continuity, occlusion fidelity, and lower speckle noise than representative layer-based and point-based methods, and improves the average PSNR and SSIM by approximately 3 dB and 0.15, respectively, over Hogel-Free Holography. Optical experiments further confirm the physical feasibility and robustness of the proposed framework. Full article

Multidisciplinary technologies are truly driving major transformations in industries, innovating to become more efficient. The need for more efficient renewable energy systems, such as solar energy, has recently been addressed with the innovation of using holographic photonic devices to avoid solar tracking devices as much as possible. In this work, a multiplexed holographic device is created and characterized for use in front of a photocell, thereby eliminating the need for tracking systems due to its wide acceptance angle and high diffraction efficiency. Commercial Bayfol^® HX121 photopolymer was used as the holographic recording material to manufacture holograms, achieving high performance and facilitating the industrial scaling of this technique. Results obtained using the multiplexing technique enable low-frequency holograms (478 lines/mm) with a 43° acceptance angle. Using three of these devices, a 129° angular sweep is possible without the need for tracking. Full article

The aim of this review is to explore the improvement in diffraction efficiency, photosensitivity and pressure sensitivity in holographic materials containing glycerol. Glycerol is a well-known, non-toxic, water-soluble polyol compound. Glycerol polymers have attracted increased attention recently due to the diversity of the available compositions. Glycerol provides access to a range of monomers for subsequent polymerizations. Various glycerol containing polymers, including polyvinyl alcohol films, polyesters, polyethers and polycarbonates, have been investigated for different applications. It was discovered in 2009 that the addition of glycerol to the composition of water-soluble holographic photopolymers facilitates the faster formation of holograms due to greater photosensitivity. It was also discovered that the presence of glycerol in holographic photopolymers makes them highly pressure-sensitive. A new family of holographic photopolymer materials, containing glycerol and capable of recording holograms with bright reflections, was reported. The novel photopolymers are composed of glycerol, a polymeric binder, a crosslinking monomer, an initiation system, and sensitising dyes. No wet-processing of holograms is necessary. Each holographic photopolymer film contains bis-acrylamide (BA) monomer in polyvinyl alcohol matrix, triethanolamine and methylene blue dye solution, glycerol and water. It was shown that the new holographic material is capable of reaching a refractive index modulation matching that of the well-known acrylamide photopolymer material, but more quickly. The new holographic photopolymer materials are cheap and environmentally friendly. The use of glycerol to improve diffraction efficiency, photosensitivity and pressure sensitivity in holographic recording layers continues to expand. This review describes the development and applications of glycerol-containing photopolymer materials. An environmentally friendly diacetone-based photopolymer was developed. The positive effect of glycerol on N-vinylpyrrolidone photopolymer was investigated. Finally, potential opportunities for future research in the area of glycerol-containing photopolymers are outlined. Full article

Azobenzene-based hologram recording materials are well known for their rewritable and polarization-selective properties that enable polarization-multiplexed recording and high-density optical storage. High diffraction efficiency, longer retention time, and shorter response time are desirable for rewritable recording materials, but they always require a trade-off relationship. In this study, we show that by simply coating the Azobenzene-based film with multiple layers of a suitable material, these parameters can be improved simultaneously without compromise. Bilayer films and triple layer films were prepared by depositing a DNA–surfactant complex-based layer above and below the azobenzene-based poly(CACzE-MMA) copolymer layer. The hologram recording performance was evaluated in terms of the diffraction efficiency, photoresponse time, and retention behavior of the recorded gratings. Compared with monolayer copolymer films, the multilayer DNA–surfactant complex-based copolymer films exhibited enhanced diffraction efficiency and faster photoresponse. In particular, the bilayer and trilayer structures showed a marked improvement in retention time, indicating suppressed relaxation of refractive index modulation. This enhancement is attributed to molecular confinement at the DNA–surfactant complex and copolymer interfaces generated by the layered architecture. These results demonstrate that a DNA–surfactant complex-based layering approach is an effective strategy for improving hologram stability and highlight the potential of DNA–surfactant complex-derived matrices as effective alternatives to poly(methyl methacrylate) (PMMA) in holographic applications. Full article

Holography offers a wide range of solutions for see-through display applications, where holographic optical elements can act either as mirrors or as waveguide couplers. In the latter case, one of the main challenges lies in achieving efficient mass fabrication. To address this limitation, the use of wavelength shift recording has been proposed, as it eliminates the need for prisms and index matching during the recording process. These elements are typically designed as slanted holographic gratings, recorded using either transmission or reflection geometries. Photopolymers as holographic recording materials are a promising solution for such applications because of their attractive optical properties. However, their inherent volume changes affect the optical performance of the recorded elements. In this paper, we propose the use of holographic lenses as wave couplers, which enables control over additional parameters such as magnification and optical aberrations. We analyze the limitations of this recording approach when prisms are not employed, and we investigate the influence of photopolymer shrinkage on hologram quality, comparing lenses recorded using transmission and reflection holography with different focal lengths. Full article

The measurements of plankton concentration performed on various-scale registration systems are quite different from each other. This work shows that these differences are caused by the spatiotemporal structure of plankton biocenosis, as well as the features of data processing methods that take into account the scale of measurements of the corresponding methods and registration tools. Hence, this leads to the modality and periodicity of the measured plankton concentration time series, whose parameters are consistent with environmental factors. Such modality and periodicity are studied in this work by analyzing the data obtained through a natural digital holographic experiment. The paper suggests the metrics of modality and periodicity of digital holographic data characterizing their informational value. It also shows the role of the segmentation of monitoring time series at the bioindication station. The proposed approach makes it possible to link the time scales of observations with the spatial scales of the studied plankton groups. Thus, we are able to determine the spatiotemporal frameworks of bioindication estimates, reasonably plan the measurement experiments, and correctly compare the data obtained using different tools. Full article

This work investigates the performance of a polyvinyl alcohol/acrylamide-based photopolymer (PVA/AA) under pulsed and continuous-wave (CW) laser exposure for holographic recording. Using a versatile setup that allows direct comparison between both regimes, diffraction efficiency (DE), angular responses, and material parameters were analyzed. Comparable maximum DE was achieved with both CW and pulsed laser exposure; however, the pulsed regime produces stronger attenuation along the grating depth, which emphasizes the need to lower the dye concentration. Furthermore, the temporal evolution of DE reveals a smaller influence of oxygen inhibition under CW exposure. Finally, second-order angular reconstructions confirm that pulsed gratings exhibit a better sinusoidal modulation, especially at low frequency rates. These results enhance the understanding of how pulsed exposure affects holographic recording and open pathways for optimizing photopolymer systems in advanced technologies. Full article