Crystal Modulator Research Articles

Improving Oxygen-Redox-Active Layered Oxide Cathodes for Sodium-Ion Batteries Through Crystal Facet Modulation and Fluorinated Interfacial Engineering.

Layered oxides with active oxygen redox are attractive cathode materials for sodium-ion batteries (SIBs) due to high capacity but suffer from rapid capacity/voltage deterioration and sluggish reaction kinetics stemming from lattice oxygen release, interfacial side reactions, and structural reconstruction. Herein, a synergistic strategy of crystal-facet modulation and fluorinated interfacial engineering is proposed to achieve high capacity, superior rate capability, and long cycle stability in Na0.67Li0.24Mn0.76O2. The synthesized single-crystal Na0.67Li0.24Mn0.76O2 (NLMO{010}) featuring increased {010} active facet exposure exhibits faster anionic redox kinetics and delivers a high capacity (272.4 mAh g-1 at 10mA g-1) with superior energy density (713.9Wh kg-1) and rate performance (116.4 mAh g-1 at 1 A g-1). Moreover, by incorporating N-Fluorobenzenesulfonimide (NFBS) as electrolyte additive, the NLMO{010} cathode retains 84.6% capacity after 400 cycles at 500mA g-1 with alleviated voltage fade (0.27mV per cycle). Combined in situ analysis and theoretical calculations unveil dual functionality of NFBS, which results in thin yet durable fluorinated interfaces on the NLMO{010} cathode and hard carbon anode and scavenges highly reactive oxygen species. The results indicate the importance of fast-ion-transfer facet engineering and fluorinated electrolyte formulation to enhance oxygen redox-active cathode materials for high-energy-density SIBs.

Ultrafast visible fiber laser mode-locked by frequency-shifted feedback of an α-BaTeMo2O9 crystal acousto-optic modulator.

We report the first demonstration, to the best of our knowledge, of visible mode-locked fiber laser using frequency-shifted feedback (FSF) with a visible α-BaTeMo2O9 (α-BTM) crystal acousto-optic modulator (AOM). First, an α-BTM crystal is used as the visible high-quality AOM with a high diffraction efficiency of 85%, a fast rise/fall time of 79/98 ns, and a low insertion loss of 0.2 dB at 635 nm. Then, the 635 nm FSF mode-locked fiber laser is achieved using a Pr3+:doped ZBLAN double-clad fiber as a visible gain medium and the α-BTM AOM as a frequency-shifting element. Self-starting mode-locking at 635 nm directly generates red laser pulses with a pulse duration of 45 ps and a repetition frequency of 31.8 MHz. Furthermore, we investigate the evolution of mode-locking dynamics as the α-BTW-AOM feedback-frequency, which helps further understand the FSF dynamics by directly generating visible ultrashort pulses.

Crystal Modulation of Mn-Based Layered Oxide toward Long-Enduring Anionic Redox with Fast Kinetics for Sodium-Ion Batteries.

Mn-based layered oxide cathodes for sodium-ion batteries with anionic redox reactions hold great potential for energy storage applications due to their ultra-high capacity and cost effectiveness. However, achieving high capacity requires overcoming challenges such as oxygen-redox failure, sluggish kinetics, and structural degradation. Herein, we employ an innovative crystal modulation strategy, using Mn-based Na0.72Li0.24Mn0.76O2 as a representative cathode material, which shows that the highly exposed {010} active facets enable an enhanced rate capability (119.6 mAh g-1 at 10C) with fast kinetics. Meanwhile, the reinforced Mn-O bond inhibits excessive oxidation of lattice oxygen and O-O cohesion loss, stabilizing and maintaining a long-enduring reversible oxygen-redox activity (100% high capacity retention after 100 cycles at 0.5C and 84.28% retention after 300 cycles at 5C). Time-resolved operando two-dimensional X-ray diffraction reveals the robust structural stability, zero-strain behavior, and suppressed phase transition with ultra-low volume variation during cycling at different rates (0.1C: 1.75%, 1C: 0.31%, 5C: 0.04%). Additionally, the full cell coupled with hard carbon achieves a high energy density of approximately 211 Wh kg-1 with superior performance. This work highlights the significance of crystal modulation and presents a universal approach in developing Mn-based oxide cathodes with stable anionic redox for high-performance sodium-ion batteries.

Crystal Modulation of Mn‐Based Layered Oxide toward Long‐Enduring Anionic Redox with Fast Kinetics for Sodium‐Ion Batteries

Mn‐based layered oxide cathodes for sodium‐ion batteries with anionic redox reactions hold great potential for energy storage applications due to their ultra‐high capacity and cost effectiveness. However, achieving high capacity requires overcoming challenges such as oxygen‐redox failure, sluggish kinetics, and structural degradation. Herein, we employ an innovative crystal modulation strategy, using Mn‐based Na0.72Li0.24Mn0.76O2 as a representative cathode material, which shows that the highly exposed {010} active facets enable an enhanced rate capability (119.6 mAh g−1 at 10C) with fast kinetics. Meanwhile, the reinforced Mn–O bond inhibits excessive oxidation of lattice oxygen and O–O cohesion loss, stabilizing and maintaining a long‐enduring reversible oxygen‐redox activity (100% high capacity retention after 100 cycles at 0.5C and 84.28% retention after 300 cycles at 5C). Time‐resolved operando two‐dimensional X‐ray diffraction reveals the robust structural stability, zero‐strain behavior, and suppressed phase transition with ultra‐low volume variation during cycling at different rates (0.1C: 1.75%, 1C: 0.31%, 5C: 0.04%). Additionally, the full cell coupled with hard carbon achieves a high energy density of approximately 211 Wh kg−1 with superior performance. This work highlights the significance of crystal modulation and presents a universal approach in developing Mn‐based oxide cathodes with stable anionic redox for high‐performance sodium‐ion batteries.

Preparation of hydrogen evolution electrode from nickel slag: Crystal surface modulation and selective growth

Preparation of hydrogen evolution electrode from nickel slag: Crystal surface modulation and selective growth

Research on the Laser Scattering Characteristics of Three-Dimensional Imaging Based on Electro–Optical Crystal Modulation

In this paper, we construct a laser 3D imaging simulation model based on the 3D imaging principle of electro–optical crystal modulation. Unlike the traditional 3D imaging simulation method, this paper focuses on the laser scattering characteristics of the target scene. To accurately analyze and simulate the scattering characteristic model of the target under laser irradiation, we propose a BRDF (Bidirectional Reflectance Distribution Function) model fitting algorithm based on the hybrid BBO–Firefly model, which can accurately simulate the laser scattering distribution of the target at different angles. Finally, according to the fitted scattering characteristic model, we inverted the target imaging gray map. We used the laser 3D imaging restoration principle to reconstruct the 3D point cloud of the target to realize the laser 3D imaging of the target.

Prussian Blue Analogue‐Based Materials: Synthesis and Their Application in Peroxymonosulfate Activation for Wastewater Treatment

Peroxymonosulfate (PMS) based advanced oxidation processes (AOPs) are effective in degrading refractory organic pollutants in water. The unique internal chemical tunability of Prussian blue analogues (PBAs), a type of metal‐organic framework materials (MOFs), makes them promising catalysts for PMS‐AOPs. However, the pristine PBA is limited in practical application due to its structural instability and easy leaching of metal ions. To this end, various methods have been developed to enhance the catalytic performance of PBAs. In this paper, the recent advances in the modification and composite strategies of PBA catalysts are systematically reviewed. PBA modification by the regulation of synthesis conditions and post‐synthesis treatment, along with composite strategies involving metal and non‐metal based materials are introduced. The structural morphology improvement, physical and chemical property adjustment, vacancy design and crystal surface modulation of PBAs induced by these modification and composite strategies are discussed in depth. In addition, the performance of the modified and composite catalysts to activate PMS for organic pollutant degradation is demonstrated. The radical pathway via SO4•‐, •OH and O2•‐, non‐radical pathway through 1O2, electron transfer process and high‐valence metal‐oxygen species, or a combination of radical and non‐radical pathways are revealed in PMS‐AOPs with PBAs and their derivatives as catalysts.

Recent Progress in Electro‐Optic Modulators: Physical Phenomenon, Structures Properties, and Integration Strategy

AbstractElectro‐optic modulators (EOMs), serving as indispensable components within photonic integrated circuits, are essential for enabling energy‐efficient, high‐speed, and high‐capacity optical communication systems. This review illustrates the principal physical phenomenon exploited in EOMs and provides a comprehensive analysis of the cutting‐edge EOMs featuring interference structures (Mach–Zehnder modulators and Michelson‐interferometer modulators) and resonance structures (microring modulators, racetrack modulators, and photonic crystal modulators). The comparative analysis of the performance merits and limitations in EOMs is presented, highlighting the combination of diverse electro‐optic material compositions with different optical structures, which reveals a promising integration strategic so as to pursue a trade‐off in modulation performance. It is contributed to the ongoing discourse on optimizing EOMs for the subsequent communication technologies and the advancement of photonic chips.

Binary amplitude holograms for shaping complex light fields with digital micromirror devices

Abstract Digital micromirror devices are a popular type of spatial light modulators for wavefront shaping applications. While they offer several advantages when compared to liquid crystal modulators, such as polarization insensitivity and rapid-switching, they only provide a binary amplitude modulation. Despite this restriction, it is possible to use binary holograms to modulate both the amplitude and phase of the incoming light, thus allowing the creation of complex light fields. Here, a didactic exploration of various types of binary holograms is presented. A particular emphasis is placed on the fact that the finite number of pixels coupled with the binary modulation limits the number of complex values that can be encoded into the holograms. This entails an inevitable trade-off between the number of complex values that can be modulated with the hologram and the number of independent degrees of freedom available to shape light, both of which impact the quality of the shaped field. Nonetheless, it is shown that by appropriately choosing the type of hologram and its parameters, it is possible to find a suitable compromise that allows shaping a wide range of complex fields with high accuracy. In particular, it is shown that choosing the appropriate alignment between the hologram and the micromirror array allows for maximizing the number of complex values. Likewise, the implications of the type of hologram and its parameters on the diffraction efficiency are also considered.

Enhancing Color Gamut with Wavelength‐Selective Polarization Modulation in Chiral Liquid Crystals

Enhancing Color Gamut with Wavelength‐Selective Polarization Modulation in Chiral Liquid Crystals

Using Post‐Treatment Additives for Crystal Modulation and Interface Passivation Enables the Fabrication of Efficient and Stable Perovskite Solar Cells in Air

AbstractHigh‐performance perovskite solar cells (PSCs) fabricated in ambient air are considered inevitable for low‐cost commercial manufacturing. However, passivating perovskite film defects and controlling the crystallization process are critical for achieving high performance in PSCs. This study proposes using the novel 2D material MBene in green antisolvent to simultaneously modulate the crystallization and passivation defects of perovskites. MBene facilitates the passivation of uncoordinated Pb2+ ions, thereby enhancing the formation energy of vacancies within the perovskite film and adjusting the energy level structure. Moreover, MBene increases nucleation sites for perovskite, significantly extending crystal growth and improving film crystallinity, thereby reducing non‐radiative recombination. Consequently, champion devices treated with MBene achieve a power conversion efficiency (PCE) of 24.22% when fabricated in air, and exhibit superior humidity and long‐term stability. Furthermore, PSCs with added MBene exhibit significant long‐term stability under various environmental conditions, including humidity and heat. The study results lay a foundation for the development of MBene materials in photovoltaics, revealing their mechanism as a new type of 2D material in perovskites, and providing new insights for industrially producing efficient and stable solar cells.

Exploring the mechanisms of benzanilide crystal growth and morphology: Crystal surface structure, solvent diffusion and solvent-interface interactions

Flaky crystals are fragile, rendering them unsuitable for various applications including use, processing, storage and transportation. This work investigates the growth and morphology regulation mechanisms of flaky crystals using benzanilide as a model material. Initially, block-like crystals are prepared by solvent screening and cooling crystallization with its morphology greatly improved. Subsequently, growth kinetics of (111), (1–10) and (020) faces are established with crystal growth experiments. The crystal growth of (001) face is also determined to follow a two-dimensional nucleation model with the microscopic surface analysis using atomic force microscopy. The changes of the surface integration resistance and the growth step height are regarded as kinetic mechanisms of the growth behavior and crystal morphology modulation by solvent and supersaturation. Finally, the molecular mechanism of the modulation of the solvent in crystal morphology is revealed base on crystal surface structure analysis and molecular dynamics simulations. The weak solvent-interface polar interactions facilitate the incorporation of benzanilide molecules into the weak polarity (001) face, leading to the surface roughening and increased crystal thickness when employing strongly polar solvents such as acetonitrile. Unlike the former, the relatively weak hydrogen bonding interactions between solvents and strong polarity (020) face, and the higher diffusion ability of molecules promote the rapid growth and disappearance of (020) face in ethanol and acetonitrile with strong hydrogen bond formation ability. This study can contribute to a deeper understanding of the solvent effect on crystal morphology and provide guidance for optimizing crystallization conditions to obtain shape-tailored crystal products.

Antimony-mediated few-layer metallic MoSe2 with rich selenium vacancies for ultrafast sodium/potassium storage

Transition metal dichalcogenides with sandwich structure possess high theoretical capacity, while face the challenge of inferior inherent electronic conductivity and dramatic volume fluctuation during cycling, lessening their fascination for electrochemical energy storage material applications. Herein, we report a crystal phase modulation strategy to modulate the electronic structure by doping cation (Sb) into the few-layer 2H-phase MoSe2 lattice, thereby implants abundant selenium vacancies and expands the layer spacing, which transforms it into a 1T-phase (T-MoSe2/C-1). The few-layer 1T-MoSe2 nanosheets are confined within chlorella-derived N, P-doped bio-carbon, endowing T-MoSe2/C-1 with a rock-solid structure, rapid Na+/K+ transport kinetics, and high reversibility. Density functional theory calculations confirm that the antimony atoms in T-MoSe2/C-1 system significantly increase the electronic conductivity, decrease the Na+/K+ diffusion barrier and reinforce the adsorbed capability for Na+/K+. Consequently, the T-MoSe2/C-1 achieves a reversible capacity of 540 mAh/g at 0.5 A/g and delivers as high as 333 mAh/g even at a high rate of 25 A/g for SIBs. As the anode of PIBs, it maintains a stable capacity of 210 mAh/g after 1,000 cycles at 5 A/g. This study provides a new horizon on the phase regulation of transition metal dichalcogenides (TMDs) to improve sodium/potassium-ions storage.

Interference patterns of two-photon excited fluorescence by spatial beam shaping

We report on two-photon excited fluorescence interference patterns produced by spatial laser beam shaping. Thereto, a focused spatially modulated laser beam component is overlapped with an unfocused Gaussian beam component, and both are directed on a cuvette filled with dye. The phase retardance between the two common path laser components is precisely adjusted by a 2D liquid crystal modulator. With this method it is possible to generate various fluorescence patterns which exhibit sharp features and a high contrast due to constructive and destructive interference of a two-photon excitation process. The developed spatial shaping interference technique with two-photon excitations has a high potential for optical and biophotonic imaging applications.

Broadband low-loss polarization-insensitive graphene-integrated photonic crystal fiber modulators in the near-infrared range

The amplitude modulator with the function of converting electric signal to optical amplitude modulation is a key component in high-speed optical communication links. In this paper, we demonstrate a variety of two-dimensional graphene-integrated photonic crystal fiber modulators for efficient near-infrared amplitude modulation with ultra-low insertion loss. Taking the advantages of the perfect total internal reflection of the porous photonic crystal fiber and flexible tunability of the graphene conductivity, the modulation depth of 0.075 dB μm−1 with a low optical loss of 2.13 × 10−4 dB μm−1, a long propagation length of ∼20 mm and polarization-insensitive characteristics in a wide wavelength of 1.3 to 1.8 μm can be achieved. This high-performance modulator may have great potential applications in various high-speed telecommunication, interconnection, and graphene-based integrated photonic systems.

Achieving the Birefringence Optimization by Methyl Modulation in Organic Nonlinear Optical Crystals

AbstractNon‐centrosymmetric organics are promising nonlinear optical (NLO) candidates, which always exhibit a short UV absorption cutoff edge, and a strong second harmonic generation (SHG) response, but an overlarge birefringence. Here, in order to optimize the birefringence, the methyl modulation of π‐conjugated organic planar units is proposed and implemented with the urea structure as a template. Thus, N‐methylurea and N,N'‐dimethylurea crystals are obtained by partially replacing hydrogen atoms with methyl groups. This replacement reduces hydrogen donors and weakens interchain hydrogen bonds, which facilitates the decreasing density and the parallel arrangement of π‐conjugated planar units. Hence, both N‐methylurea and N,N'‐dimethylurea crystals exhibit not only an optimized birefringence (N‐methylurea ≈0.099 and N,N'‐dimethylurea ≈0.072 at 546 nm) but also an enhanced SHG response (N‐methylurea ≈1.2 × β‐BaB2O4 and N,N'‐dimethylurea ≈1.9 × β‐BaB2O4), while maintaining a short UV absorption cutoff edge. Therefore, this work provides a novel strategy for the structural design and performance modulation of organic NLO crystals.

Dynamic geometric phase holography based on in-plane switching liquid crystal

ABSTRACT Liquid crystal geometric phase modulation technology is expected to achieve thin, small and achromatic spatial light modulation, which in turn has the potential to achieve holographic displays with large field angles and high clarity. This article presents a continuous dynamic geometric phase liquid crystal spatial light modulation method based on in-plane switching (IPS) mode. The relationship between geometric phase modulation and driving voltage is calibrated by using interferometry. Two hundred fifty-six phase orders within the phase modulation range of 0~π/2 is achieved. Subsequently, a phase hologram with a modulation range of 0~π/2 was designed by combining the GS (Gerchberg-Saxton) algorithm and single Fourier transform, demonstrating the holographic display capability. This article provides a low-cost approach for dynamic geometric phase holographic display.

Design Optimisation of a Flat-Panel, Limited-Angle TOF-PET Scanner: A Simulation Study.

In time-of-flight positron emission tomography (TOF-PET), a coincidence time resolution (CTR) below 100 ps reduces the angular coverage requirements and, thus, the geometric constraints of the scanner design. Among other possibilities, this opens the possibility of using flat-panel PET detectors. Such a design would be more cost-accessible and compact and allow for a higher degree of modularity than a conventional ring scanner. However, achieving adequate CTR is a considerable challenge and requires improvements at every level of detection. Based on recent results in the ongoing development of optimised TOF-PET photodetectors and electronics, we expect that within a few years, a CTR of about 75 ps will be be achievable at the system level. In this work, flat-panel scanners with four panels and various design parameters were simulated, assessed and compared to a reference scanner based on the Siemens Biograph Vision using NEMA NU 2-2018 metrics. Point sources were also simulated, and a method for evaluating spatial resolution that is more appropriate for flat-panel geometry is presented. We also studied the effects of crystal readout strategies, comparing single-crystal and module readout levels. The results demonstrate that with a CTR below 100 ps, a flat-panel scanner can achieve image quality comparable to that of a reference clinical scanner, with considerable savings in scintillator material.

Pretilt angle modulation of liquid crystals based on single crystal rubrene with incorporation of homeotropic polyimides

The alignment control of liquid crystals (LCs) is critical for various practical applications. The pretilt angle modulation of LCs typically requires a mechanical rubbing on substrates to orient the LCs. This study presents a contact-free approach to achieve pretilt angle modulation of LCs. Initially, a single crystal rubrene (SCR) film is deposited on the substrate. Subsequently, a mixture of nematic LCs and homeotropic polyimides (HPIs) is introduced between two SCR substrates via capillary action. During capillary filling, the synergy of capillary flow and the interaction between LCs and SCR ensures specific LC orientation. Subsequently, HPI dopants migrate toward and organize on the SCR through vertical phase separation, enhancing surface hydrophobicity and thereby increasing the pretilt angle of LCs. The pretilt angle of LCs can be continuously adjusted over a wide range from 2° to 90° by varying the HPI concentration. The contact-free process preserves against electrostatic charges, dust contamination, and surface damage typical of rubbed LC cells. This believed to be novel technique shows promise for developing no-bias-bend and bistable bend-splay LC displays.

Highly efficient tunable mid-infrared luminescence achieved by crystal field modulation of CsPb1-xHoxBr3 halide perovskite AlF3-based fluoride glass

Mid-infrared (MIR) light sources have gained significant importance across various applications in spectroscopy, sensing, astronomy, communications and medical surgery. The diverse spectral characteristics of rare earth ions, particularly lanthanide ions, stemming from their distinctive 4f intershell transitions, offer a multitude of potential transitions spanning the UV-visible-infrared spectrum. Despite recent advancements in MIR gain luminescence, the investigation of tunable MIR luminescence mechanisms remains a major technical challenge. Herein, an effective mechanism to modulate the local crystal field of rare earth ions by altering its crystal structure has been revealed, resulting in tunable broad-spectrum emission in the MIR luminescence range of 2800-3000 nm and multi-peak emission in the near-infrared band of Ho3+. Notably, the local crystal field of Ho3+ is adjusted by manipulating the lattice symmetry of CsPb1-xHoxBr3 perovskite through the incorporation of fluoride glass reticulation to control the crystal size of the perovskite and thereby modify the lattice symmetry of CsPb1-xHoxBr3 perovskite. The energy level transition of Ho3+ is influenced by adjusting the crystal field asymmetry, resulting in the splitting of the 5I6 energy level depending on the crystal field. This cleavage affects the transitions from the 5I5 level to 5I6 at 1480 nm and from 5I6 to 5I7 at 2880 nm. As 5I6 acts as the common upper level for the two emission peaks, the infrared peaks at 1480 nm and 2880 nm widen and develop into a dual-peak emission phenomenon. The infrared luminescence produced aligns closely with the distinctive infrared absorption peaks of carbon dioxide, leading to the development of a convenient, high-precision device for monitoring of CO2 concentration in hydrogen energy in real time. These findings are anticipated to pave the way for extensive utilization of novel tunable MIR luminescence.