Metasurfaces, as the ultrathin version of metamaterials, have caught growing attention due to their superior capability in controlling the phase, amplitude and polarization states of light. Among various types of metasurfaces, geometric metasurface that encodes a geometric or Pancharatnam-Berry phase into the orientation angle of the constituent meta-atoms has shown great potential in controlling light in both linear and nonlinear optical regimes. The robust and dispersionless nature of the geometric phase simplifies the wave manipulation tremendously. Benefitting from the continuous phase control, metasurface holography has exhibited advantages over conventional depth controlled holography with discretized phase levels. Here we report on spin and wavelength multiplexed nonlinear metasurface holography, which allows construction of multiple target holographic images carried independently by the fundamental and harmonic generation waves of different spins. The nonlinear holograms provide independent, nondispersive and crosstalk-free post-selective channels for holographic multiplexing and multidimensional optical data storages, anti-counterfeiting, and optical encryption.

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Spin and wavelength multiplexed nonlinear metasurface holography.

Layer-based method has been proposed as an efficient approach to calculate holograms for holographic image display. This paper further improves its calculation speed and depth cues quality by introducing three different techniques, an improved coding scheme, a multilayer depth- fused 3D method and a fraction method. As a result the total computation time is reduced more than 4 times, and holographic images with accommodation cue are calculated in real time to interactions with the displayed image in a proof-of-concept setting of head-mounted holographic displays.

Improved layer-based method for rapid hologram generation and real-time interactive holographic display applications

The multiplexing encoding method is proposed and demonstrated for reconstructing colorful images accurately by using single phase-only spatial light modulator (SLM). It will encode the light waves at different wavelengths into one pure-phase hologram at the same time based on the analytic formulas. The three-dimensional (3D) images can be reconstructed clearly when the light waves at different wavelengths are incident into the encoding hologram. Numerical simulations and optical experiments for 2D and 3D colorful images are performed. The results show that the colorful reconstructed images with high quality are achieved successfully. The proposed multiplexing method is a simple and fast encoding approach and the size of the system is small and compact. It is expected to be used for realizing full-color 3D holographic display in future.

Multiplexing encoding method for full-color dynamic 3D holographic display.

Dynamic holographic three-dimensional (3-D) display, which features reconstructing 3-D images with full depth cues has great potential in various fields such as medical, and military industries obtained a broad attention in the last decades. Combing parallel computation techniques, hologram synthesis algorithms are capable of calculating diffraction and interference pattern dynamically or even in real-time manner. In addition, the development of various types of optical modulators including liquid crystal (LC)-based, opto-acoustic-typed, digital micromirror devices (DMDs), and opto–opto materials made it possible that device can load and display such holographic patterns dynamically. In accordance with the progress of algorithms and modulators, we can expect that dynamic holographic 3-D display will be able to reconstruct 3-D images with real-time refresh rate, full color, wide viewing angle, and large image size, and the system will be commercialized in a near future.

A Review of Dynamic Holographic Three-Dimensional Display: Algorithms, Devices, and Systems

Optical holography for recording three-dimensional (3-D) scenes can be traced back to the early sixties. Since then, the art of holography has been applied in many areas, primarily as a tool for 3-D imaging, processing, and display. Extension of optical holography to other disciplines, such as optical computing and encryption, has been explored, but the scope of development is relatively limited. However, with the rapid advancements in electronics, computing, and material science technologies, most of the optical processes can be substituted with numerical or digital hardware means, thus leading to the emergence of digital holography. A typical digital holography framework can be encapsulated into three major stages, namely the input, processing, and output stages. The input and output stages are gatekeepers connecting the optical and digital worlds, without which the study on digital holography could only be restricted to theoretical and numerical analysis. In the past few decades, numerous research works have been conducted on these two important areas. In this paper, we shall provide a review on the recent development in these two important areas of digital holography. Selected pieces of important and popular works on the acquisition and display of digital holograms will be reported.

Review on the State-of-the-Art Technologies for Acquisition and Display of Digital Holograms

A fast algorithm with low memory usage is proposed to generate the hologram for full-color 3D display based on a compressed look-up table (C-LUT). The C-LUT is described and built to reduce the memory usage and speed up the calculation of the computer-generated hologram (CGH). Numerical simulations and optical experiments are performed to confirm this method, and several other algorithms are compared. The results show that the memory usage of the C-LUT is kept low when number of depth layers of the 3D object is increased, and the time for building the C-LUT is independent of the number of depth layers of the 3D object. The algorithm based on C-LUT is an efficient method for saving memory usage and calculation time, and it is expected that it could be used for realizing real-time and full-color 3D holographic display in the future.

Reducing the memory usage for effective computer-generated hologram calculation using compressed look-up table in full-color holographic display.

A Mof-Based Trap with Strong Affinity Toward Low-Concentration Heavy Metal Ions

BACKGROUND Efficient pretreatment is key to improving landfill leachate biodegradability. This is the first study to combine hydrodynamic cavitation (HC) and potassium ferrate (K2FeO4) for the treatment of landfill leachate, using chemical oxygen demand (COD) and UV absorbance at a wavelength of 254 nm (UV254) as the main test indicators. The feasibility of HC combined with K2FeO4 as a mature leachate pretreatment method was explored. RESULTS The HC experiment used 40 L of mature landfill leachate raw water, with optimal reaction conditions of: pH 4, 70 min continuous cavitation and K2FeO4 dosage of 1.5 g/l. The leachate COD decreased from 3812.64 mg/l to 1833.8 mg/l (51.69% removal), while UV254 decreased from 20.44 to 6.14 (65.14% removal) and total organic carbon decreased from 1489 mg/l to 915.3 mg/l (38.53% removal). After HC/K2FeO4 treatment, the biochemical oxygen demand after 5 days (BOD5) /COD (0.61) was greatly improved compared to the raw leachate (0.362), with effluent reaching the standard (BOD5/COD>0.6) required to be considered fully biodegradable. Studies have shown that HC can accelerate the reaction rate of Fe(VI) with pollutants, while also forming a Fenton-like system with the products of Fe(VI) reduction. FT-IR analysis results showed that HC/K2FeO4 treatment achieved the removal of complex high molecular weight compounds, by carbonization or decomposition into more biodegradable substances. CONCLUSION Compared with the traditional pretreatment process, HC/K2FeO4 exhibits strong oxidation and coagulation performance, achieving the significant removal of leachate humus and effectively improving biodegradability, while also being suitable for large-scale applications, such as landfill leachate treatment. This article is protected by copyright. All rights reserved. 

A novel process for landfill leachate pretreatment using hydrodynamic cavitation combined with potassium ferrate oxidation

The purpose of this study was to optimize the extraction conditions for separating Co2+ from Ni2+ using N-butylamine phosphinate ionic liquid of [C4H9NH3][Cyanex 272]. A Box–Behnken design of response surface methodology was used to analyze the effects of the initial pH, extraction time, and extraction temperature on the separation factor of Co2+ from sulfuric acid solution containing Ni2+. The concentrations of Co2+ and Ni2+ in an aqueous solution were determined using inductively coupled plasma-optical emission spectrometry. The optimized extraction conditions were as follows: an initial pH of 3.7, an extraction time of 55.8 min, and an extraction temperature of 330.4 K. The separation factor of Co2+ from Ni2+ under optimized extraction conditions was 66.1, which was very close to the predicted value of 67.2, and the error was 1.7%. The equation for single-stage extraction with high reliability can be used for optimizing the multi-stage extraction process of Co2+ from Ni2+. The stoichiometry of chemical reaction for ion-exchange extraction was also investigated using the slope method.

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Single-Stage Extraction and Separation of Co2+ from Ni2+ Using Ionic Liquid of [C4H9NH3][Cyanex 272]

Lead is the main toxic factor in jarosite residue. It is important to study the release behavior of lead from simulated lead-bearing jarosite (SLBJ) for predicting the stability of jarosite residue and its secondary pollution to the environment. To identify the technical issues and limitations associated with its safe disposal, a comprehensive analysis of the chemical, structural, and morphological characteristics of SLBJ was conducted using various detection techniques including XRF, XRD, SEM-EDS, FTIR, XPS, etc. The environmental stability of SLBJ was assessed through the toxicity characteristic leaching procedure (TCLP), Chinese standard leaching tests (CSLT), and a long-term leaching experiment (LTLE). Phase composition analysis revealed that the primary components of SLBJ are sodium jarosite and lead sulfate. TCLP and CSLT results indicated that lead content surpassed the toxicity identification standard limit by more than 47 times. Furthermore, LTLE indicated that the lead concentration surpassed the standard limit about 15 times after prolonged contact time. This study is of great significance for predicting the stability of jarosite residue and its secondary pollution to the environment.

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Zhumei Sun

Papers

Reducing the memory usage for effective computer-generated hologram calculation using compressed look-up table in full-color holographic display.

A Mof-Based Trap with Strong Affinity Toward Low-Concentration Heavy Metal Ions

A novel process for landfill leachate pretreatment using hydrodynamic cavitation combined with potassium ferrate oxidation

Single-Stage Extraction and Separation of Co2+ from Ni2+ Using Ionic Liquid of [C4H9NH3][Cyanex 272]

The Synthesis of Lead-Bearing Jarosite and Its Occurrence Characteristic and Leaching Toxicity Evaluation