Search

Metasurface holography offers significant advantages, including a broad field of view, minimal noise, and high imaging quality, making it valuable across various optical domains such as 3D displays, VR, and color displays. However, most passive pure-structured metasurface holographic devices face a limitation: once fabricated, as their functionality remains fixed. In recent developments, the introduction of multiplexed and reconfigurable metasurfaces breaks this limitation. Here, the comprehensive progress in holography from single metasurfaces to multiplexed and reconfigurable metasurfaces is reviewed. First, single metasurface holography is briefly introduced. Second, the latest progress in angular momentum multiplexed metasurface holography, including basic characteristics, design strategies, and diverse applications, is discussed. Next, a detailed overview of wavelength-sensitive, angle-sensitive, and polarization-controlled holograms is considered. The recent progress in reconfigurable metasurface holography based on lumped elements is highlighted. Its instant on-site programmability combined with machine learning provides the possibility of realizing movie-like dynamic holographic displays. Finally, we briefly summarize this rapidly growing area of research, proposing future directions and potential applications. [ABSTRACT FROM AUTHOR]

All‐optical diffractive neural networks (DNNs) based on passive structures have been shown to perform complicated functions by optical acceleration, thus reforming in situ applications requiring digital computing processing. Its stable, compact, and passive features make it suitable for many conventional applications in complex electromagnetic environments. Here, a DNN based on a multilayer passive metasurface array is presented to estimate the information of arrival (IOA) over a wide range of frequency bands and incident angles. Unlike traditional methods, multiple correlated or coherent electromagnetic signals interfere with each other, resulting in difficult separation which is a fundamental obstacle in multi‐source IOA detection. Here, the proposed diffraction system creates separate virtual channels to isolate and process different incoming waves. It recognizes and classifies the beams, focuses them on the output plane divided by the arrival angle and working frequency, and displays the IOA and number of sources in real time at the speed of light. Furthermore, the massive‐parallelism and data‐post‐processing‐free strategy allows for broader applications in harsh environments, such as seismic detection and underwater circumstances. [ABSTRACT FROM AUTHOR]

AbstractAs a high-precision instrument, electronic pressure scanners have a crucial role in multi-point pressure measurements. However, the internal piezoresistive components drift with temperature, and this phenomenon has become a key factor restricting the accuracy. In this study, a hybrid algorithm based on back propagation neural network (BPNN) with particle swarm optimization (PSO) and gravity search algorithm (GSA) is reported for multi-channel temperature compensation to solve this problem Fundamentally, the global optimization search capability of GSA and the fast local convergence advantage of PSO are utilized so that the model parameters of the BPNN are guaranteed to be reliable and the efficiency of its execution is further improved. To this end, the temperature data between −40 °C and 70 °C obtained through the calibration experimental system are analyzed for compensation of the electronic pressure scanner from the 0 to 700 kPa adiabatic range. The results show that, compared with BP neural network, radial basis function (RBF) neural network, and PSO-BP method, the new PSOGSA-BP approach has higher accuracy in pressure sensor temperature compensation, in which the absolute error is only 0.2301 kPa and the full-scale error is 0.03% full scale. In addition, the method can be applied to electronic pressure scanners with stronger generalization and demonstrated to be suitable for temperature compensation. [ABSTRACT FROM AUTHOR]

Hiding an isolated object in free space using a transmissive invisibility cloak has become a significant research area, propelled by advancements in metamaterials and transformation optics over the past decade. Despite the availability of various simplified methods for implementing transmissive cloaks, issues such as impedance mismatches and narrow working bandwidths often arise, posing challenges. Achieving a broadband transmissive cloak in free space has proven to be particularly arduous. This study presents a near‐perfect one‐directional broadband transmissive cloak constructed from multilayer metasurfaces of arbitrary shapes, showcasing superior performance across a broadband frequency range. The phase distribution of the metasurfaces and the efficacy of the transmissive cloak are assessed using the generalized Snell's law. An experimental near‐perfect broadband transmissive cloak is successfully demonstrated to operate within the frequency range of 8.5 to 11.2 GHz. This study contributes to reducing the density and mass of cloaks, thereby facilitating the expansion of cloaking capabilities in various directions and across different frequency bands. [ABSTRACT FROM AUTHOR]

To develop a method for direct transesterification of wet yeast using immobilized lipase, the oleaginous yeast Saitozyma podzolica Zwy-2-3 and the lipase producing Burkholderia pyrrolica WZ10-3 were used as materials for production of biodiesel. Fe 3 O 4 @SiO 2 -CHO prepared by modifying Fe 3 O 4 with TEOS, APTES and glutaraldehyde. The biocatalysts covalently cross-linked with WZ10-3 lipase by Fe 3 O 4 @SiO 2 -CHO were characterized by FTIR, XRD and TEM. When the enzyme dosage, glutaraldehyde concentration, temperature and time were 30.22 mL, 2.0%, 40 °C and 4 h, the immobilized lipase activity and immobilization rate reached 10038.0 U/g and 96.9%, respectively. The optimum temperatures for immobilized and free lipase were 60 °C and 40 °C. The immobilized enzyme still had 80% enzymatic activity after 48 d storage at 4 °C. The optimized conditions for the direct conversion of immobilized lipase to esterified wet yeast (one-step) were: enzyme dosage 2.5 g, reaction temperature 35 °C; water content 15%; and molar ratio of n-hexane to methanol 3: 1. The transesterification rates of one-step method for oil and biomass were 98.12% and 56.11%, respectively. In contrast, the two-step method was only 88.75% and 51.21%. The immobilized enzyme had 90% enzyme activity after 10 times of reuse. • Fe 3 O 4 nanoparticles stabilized by different organic ligands were prepared. • Microbial lipase was immobilized on magnetic nanoparticles by covalent cross-linking. • Direct transesterification of wet oleaginous yeast for biodiesel production. • After 10 times reuse, immobilized lipase yielded >90% enzyme activity. [ABSTRACT FROM AUTHOR]

Ferroelectricity may promote photocatalytic performance because the carrier-separation efficiency can be effectively improved by the internal electrostatic field caused by spontaneous polarization. Heterostructures that combine ferroelectric materials with other semiconductor materials can be further advantageous to the photocatalysis process. In this work, Bi 1.65 Fe 1.16 Nb 1.12 O 7 was hybridized with g-C 3 N 4 via a facile low-temperature method. The results of high-resolution transmission electron microscopy confirmed that a tight interface was formed between g-C 3 N 4 and Bi 1.65 Fe 1.16 Nb 1.12 O 7 , which gave the (g-C 3 N 4 )-(Bi 1.65 Fe 1.16 Nb 1.12 O 7 ) heterojunction a more superior visible light photocatalytic performance. The degradation of rhodamine B by optimized (g-C 3 N 4 ) 0.5 -(Bi 1.65 Fe 1.16 Nb 1.12 O 7 ) 0.5 under visible light was almost 3.3 times higher than that by monomer Bi 1.65 Fe 1.16 Nb 1.12 O 7 and 7.4 times higher than that by g-C 3 N 4 . The (g-C 3 N 4 ) 0.5 -(Bi 1.65 Fe 1.16 Nb 1.12 O 7 ) 0.5 sample also showed the highest photocurrent in the photoelectrochemical tests. To further verify the benefit of the built-in electric field in terms of the photocatalytic performance, Bi 2 FeNbO 7 , with a higher spontaneous polarization, was also synthesized and hybridized with g-C 3 N 4 . Both Bi 2 FeNbO 7 and (g-C 3 N 4 ) 0.5 -(Bi 2 FeNbO 7 ) 0.5 exhibited better photocatalytic activities than those of Bi 1.65 Fe 1.16 Nb 1.12 O 7 and (g-C 3 N 4 ) 0.5 -(Bi 1.65 Fe 1.16 Nb 1.12 O 7 ) 0.5 , although the latter ones had a stronger visible-light absorbance. This implies the very promising prospects of applying ferroelectric materials for solar energy harvest.