Optical Applications Research Articles

Second harmonic generation from bound-state in the continuum-hosted few-layers van der Waals metasurface

Abstract Monolayer transition metals dichalcogenides (TMDs) have been coupled to bound-state in the continuum (BIC) hosted dielectric structures to attain high second harmonic generation (SHG). However, the transvers electric modes are strongly localized in the waveguides result in fairly weak exciton-photon coupling in monolayer TMD placed on the surface. To achieve SHG in few-layers TMDs based BIC-inspired structure is a challenge. Here, we report BIC in few-layers TMDs metasurface with high quality factor (Q-factor), tunability, and modes-upholding in different environments. The metasurface sustains BIC at different thickness of the meta-atoms, which is highly desired for maintaining the accuracy in fabrications. Next, we calculate the SHG efficiency from few-layers TMD metasurface around BIC wavelengths. The high conversion efficiency in this work is 1.47 × 10−4 for 6 mW incident power. Moreover, our design is highly thin and can be used for various linear and non-linear applications in optics. This study will provide a new route to next generation post-silicon metasurfaces.

Dual- and quad-FSF laser optical frequency comb application for time delay variation associated measurements

The frequency-shifted feedback (FSF) laser is an optoelectronic system with an optical feedback loop with a characteristic feature that consists of a broadband optical emission spectrum that does not contain modes. Nevertheless, this system may operate in the so-called mode-locking regime, when the output optical signal is a sequence of short optical pulses with a repetition rate determined by the delay time in the feedback loop. In the frequency domain such a sequence forms the optical frequency comb with line spacing defined by time delay magnitude. It was shown recently that the sequential frequency down-conversion technique allows us to obtain tunable dual- and quad-combs when the FSF laser is seeded only with optical amplifier spontaneous emission. We propose to apply these combs to fulfill measurements associated with time delay variation, such as distance ranging and optical material refraction coefficient measurements.

A hydrazine-hydroxy-pyran-2-one derivatives as a potential anticancer and antibacterial agent: synthesis, spectroscopic, SC-XRD, DFT/TD-DFT, Hirshfeld surface analysis, in silico molecular docking and nonlinear optical responses studies

This study presents the synthesis and thorough characterisation of a hydrazine-hydroxy-pyran-2-one derivative referred to as compound (L1 : 3, 3′- [(1E.2E)-hydrazine-1, 2-diylidene-dieth-1-yl-1-ylidene] bis(4-hydroxy-6-methyl-2H-pyran-2-one). Structural elucidation using UV-vis, FT-IR and single crystal X-ray diffraction (SC-XRD) confirmed tautomeric forms of L1 . The SC-XRD analysis revealed a bi-zwitterionic form (BZL1 ), stabilised by the intramolecular proton transfer between two enol units and azine tautomerism. The planar molecular structure, supported by XRD, DFT and Hirshfeld surface analysis, showed charge-assisted hydrogen bonds [N+−H…O−] forming S(6) ring motifs. Crystals were stabilised by C-H…O hydrogen bonds and π-π stacking, analysed through Hirshfeld surfaces and 2D fingerprint plots. Compound L2 : 3-[(1E)-1-(9H-fluoren-9-ylidenehydrazinylidene)ethyl]-4-hydroxy-6-methyl-2H-pyran-2-one), is illustrated in this paper to compare two derivatives of dehydroacetic acid (DHA) and to enrich this study. Molecular docking revealed binding affinities of hybrid compounds with target proteins. DFT and TD-DFT analyses examined structural, electronic and optical properties, aligning well with experimental data. BZL1 exhibited higher electronic hardness (3.632 eV) than L2 (3.506 eV). Variations in α, Δα and ρ values were observed, with L1 showing stronger γ(0; 0, 0, 0) and γ(−ω; ω, 0, 0) while L2 excelled in γ(−2ω; ω, ω, 0). Consequently, these results highlight the potential of these compounds as promising candidates for use in third-order nonlinear optical applications.

Study on the modulation mechanism of the optoelectronic properties based on common electrode metal atom adsorption on graphene/MoTe2.

The two-dimensional graphene/MoTe2 heterostructure holds extensive potential applications in optoelectronic devices, sensors, and catalysts. To expand its optical applications, this study systematically investigates the adsorption stability of metal atoms (Au, Pt, Pd, and Fe) on the graphene/MoTe2 and their influence on its optoelectronic properties employing first-principles methods. The findings indicate that after the adsorption of Au and Pd, the structure retains its direct bandgap properties, while the adsorption of Pt and Fe exhibits indirect bandgap characteristics. The work functions for all adsorbed structures are lower compared to the pristine graphene/MoTe2. The total density of states is primarily derived from the C-2p, Mo-4d, Te-5p orbitals, as well as the d and s orbitals of the adsorbed atoms. The pristine graphene/MoTe2 exhibits significant absorption in the ultraviolet range. Once graphene/MoTe2 is adsorbed by metal atoms, it can significantly enhance the optical absorption across the spectrum from infrared to ultraviolet light. These findings provide important theoretical guidance for regulating the application of graphene/MoTe2 in optoelectronics and related fields. All analyses are grounded in density functional theory first principles and computed using CASTEP. Graphene/MoTe2 consists of 4 × 4 × 1 single-layer, graphene single layer, and 3 × 3 × 1 single-layer MoTe2. To prevent interactions between neighboring unit cells, a 20Å vacuum space in the z-direction is employed. The electronic exchange-correlation interactions are treated using the Perdew-Burke-Ernzerhof functional within the framework of the generalized gradient approximation. Van der Waals (vdW) interactions are incorporated using the vdW correction function proposed by Grimme, which effectively describes vdW interactions. During the simulation, the cutoff energy for plane wave expansion is set to 420eV, and the k-point grid is set to 4 × 4 × 1. The atomic displacement convergence standard is 0.002Å, the internal stress convergence standard is 0.1GPa, and the interaction force convergence standard between atoms is 0.05eV/Å. The convergence threshold for the iteration precision is set to ensure that the total energy for each atom is not less than 2 × 10-5eV/atom.

Ferroelectric Nematic Liquid Crystals Showing High Birefringence.

High birefringence nematic liquid crystals are particularly demanded for adaptive optics applications in the infrared spectrum because it enable a thinner cell gap for achieving fast response time and improved diffraction efficiency. The emerging ferroelectric nematic liquid crystals have attracted widespread interest in soft matter due to their unique combination of ferroelectricity and fluidity. However, the birefringence, which is one of the most important optical parameters in electro-optic devices, is not large enough (<0.25) in most ferroelectric nematic materials. Here, a polar liquid crystal molecule library containing more than 60 molecules with a highly rigid and fluorinated nature is developed. The introduction of triple bonds constructs a long π-electron conjugated mesogen skeleton, significantly improving the birefringence of polar liquid crystal phases. The birefringence and dispersion properties are systematically studied, demonstrating a strong dependence on chemical structures and the type of polar phases. Furthermore, through multi-component mixing, polar liquid crystal mixtures with ultra-wide temperature range and excellent stability at or near room temperature are obtained. They possess much higher birefringence than the existing ferroelectric liquid crystal materials. The unique combination of high birefringence and fluidic ferroelectricity is expected to promote the application of polar liquid crystals in electro-optic technologies.

Two-Dimensional Ferroelectric Materials: From Prediction to Applications

Ferroelectric materials hold immense potential for diverse applications in sensors, actuators, memory storage, and microelectronics. The discovery of two-dimensional (2D) ferroelectrics, particularly ultrathin compounds with stable crystal structure and room-temperature ferroelectricity, has led to significant advancements in the field. However, challenges such as depolarization effects, low Curie temperature, and high energy barriers for polarization reversal remain in the development of 2D ferroelectrics with high performance. In this review, recent progress in the discovery and design of 2D ferroelectric materials is discussed, focusing on their properties, underlying mechanisms, and applications. Based on the work discussed in this review, we look ahead to theoretical prediction for 2D ferroelectric materials and their potential applications, such as the application in nonlinear optics. The progress in theoretical and experimental research could lead to the discovery and design of next-generation nanoelectronic and optoelectronic devices, facilitating the applications of 2D ferroelectric materials in emerging advanced technologies.

Performance SiO2, GO, and SiO2@GO nanomaterials on fabricating new polymer nanocomposites for optical, antibacterial, and anticancer applications

Performance SiO2, GO, and SiO2@GO nanomaterials on fabricating new polymer nanocomposites for optical, antibacterial, and anticancer applications

All-Fiber Micro-Ring Resonator Based p-Si/n-ITO Heterojunction Electro-Optic Modulator

With the rapid advancement of information technology, the data demands in transmission rates, processing speed, and storage capacity have been increasing significantly. However, silicon electro-optic modulators, characterized by their weak electro-optic effect, struggle to balance modulation efficiency and bandwidth. To overcome this limitation, we propose an electro-optic modulator based on an all-fiber micro-ring resonator and a p-Si/n-ITO heterojunction, achieving high modulation efficiency and large bandwidth. ITO is introduced in this design, which exhibits an ε-near-zero (ENZ) effect in the communication band. The real and imaginary parts of the refractive index of ITO undergo significant changes in response to variations in carrier concentration induced by the reverse bias voltage, thereby enabling efficient electro-optic modulation. Additionally, the design of the all-fiber micro-ring eliminates coupling losses associated with spatial optical-waveguide coupling, thereby resolving the high insertion loss of silicon waveguide modulators and the challenges of integrating MZI modulation structures. The results demonstrate that this modulator can achieve significant phase shifts at low voltages, with a modulation efficiency of up to 3.08 nm/V and a bandwidth reaching 82.04 GHz, indicating its potential for high-speed optical chip applications.

Focus point on nonlinear optical systems and applications

Focus point on nonlinear optical systems and applications

Intrinsic Anti-Freezing, Tough, and Transparent Hydrogels for Smart Optical and Multi-Modal Sensing Applications.

Hydrogels have received great attention due to their molecular designability and wide application range. However, they are prone to freeze at low temperatures due to the existence of mass water molecules, which can damage their flexibility and transparency, greatly limiting their use in cold environments. Although adding cryoprotectants can reduce the freezing point of hydrogels, it may also deteriorate the mechanical properties and face the risk of cryoprotectant leakage. Herein, the microphase-separated structures of hydrogels are regulated to confine water molecules in sub-6nm nanochannels and increase the proportion of bound water, endowing the hydrogels with intrinsic anti-freezing properties, high mechanical strength, good stretchability, remarkable fracture energy, and puncture resistance. Even after being kept in liquid nitrogen for 1000h, the hydrogel still maintains good transparency. The hydrogel can exhibit excellent low-temperature shape memory and intelligent optical waveguide properties. Additionally, the hydrogel can be assembled into strain and pressure sensors for flexible sensing at both room and low temperatures. The intrinsically anti-freezing microphase-separated hydrogel offers broad prospects in low-temperature electronic and optical applications.

Insight into the Origin of Second Harmonic Generation and Rational Design in the Metal Halide Borates.

Metal halide borates are promising candidates for high-performance nonlinear optical (NLO) applications, yet the origins of their second harmonic generation (SHG) properties remain unclear. Using atom response theory combined with density functional theory calculations, this study investigates why halogen substitution leads to distinctly different SHG responses in halide monoborates (Pb2BO3X) versus halide pentaborates (Pb2B5O9X). We find that the SHG origins vary between these two families due to differences in the strength of the Pb-X interactions. Interestingly, the stereochemically active lone pairs are not shown to be the primary contributors to SHG; instead, these hybridized asymmetric orbitals can introduce negative contributions. Utilizing the deffp vs αsum/(NEg) linear relationship, we predict 12 new NLO borates with strong SHG responses, including the promising NLO material Sn2B5O9I (19.2 × KDP), which is expected to exhibit the highest SHG response among halide borates reported to date. This work provides valuable insights into the relationship between elemental substitution and SHG modulation, guiding the design of advanced NLO materials.

Mechanical Twisting-Induced Enhancement of Second-Order Optical Nonlinearity in a Flexible Molecular Crystal.

Flexible molecular crystals are essential for advancing smart materials, providing unique functionality and adaptability for applications in next-generation electronics, pharmaceuticals, and energy storage. However, the optical applications of flexible molecular crystals have been largely restricted to linear optics, with nonlinear optical (NLO) properties rarely explored. Herein, we report on the application of mechanical twisting of flexible molecular crystals for second-order nonlinear optics. The crystal formed through the self-assembly of the model compound 9-anthraldehyde (AA) features an intrinsic chiral and noncentrosymmetric structure, demonstrating high efficiency second harmonic generation (SHG) and NLO circular dichroism, which could be greatly enhanced by macroscopic mechanical twisting. The anisotropic molecular stacking imparts the AA crystal with mechanical flexibility of combined elastic bending and plastic twisting. The isochiral mechanical twisting could greatly enhance the SHG intensities by an order of magnitude depending on their M- or P-configuration. Meanwhile, the SHG circular dichroism factor gSHG-CD of the isochiral twisted crystal is greatly increased, achieving the highest reported NLO anisotropy factor among organic NLO materials. These boosted NLO performances of SHG intensity and nonlinear chiroptical response are expected to greatly expand the photonic applications of flexible molecular crystals.

Tailored Metal‐Oxygen Bonding in Amorphous Perovskite CoSnO3 for Broadband Ultrafast Laser State Active Manipulation

AbstractAmorphous perovskite CoSnO3 has attracted significant attention due to its unique properties and various modification methods. However, modifying metal‐oxygen bonds on the nonlinear optical (NLO) characteristics remains uncharted. In this study, a dehydration method is employed to convert the metal‐hydroxyl bonds (M─OH) of hydroxide CoSn(OH)6 into metal‐oxygen bonds (M─O), successfully preparing amorphous CoSnO3 with oxygen vacancies. Subsequently, effective regulation of the metal‐oxygen bonds in amorphous CoSnO3 is achieved through an ion exchange strategy, yielding Fe‐doped CoSnO3 (Fe‐CoSnO3). Comprehensive characterization and analysis revealed that the regulation of metal‐oxygen bonds accelerated the electron transition rate, resulting in a fast recovery time of ≈245.1 fs for Fe‐CoSnO3, accompanied by a significant boost in broadband NLO properties. Notably, when Fe‐CoSnO3 is utilized as a saturable absorber (SA), it exhibited superior mode‐locking characteristics compared to CoSnO3 in the range of 1–2 µm. Specifically at the communication band of 1.5 µm, the dynamic switching between single‐wavelength and dual‐wavelength mode‐locking operations is achieved. With the ultrafast laser state manipulation, a digital encoding is also demonstrated. This work confirmed that the tailoring of metal‐oxygen bonds makes Fe‐CoSnO3 an excellent NLO material for ultrafast optical applications, and this tailoring strategy provides new insights for designing advanced NLO materials.

Fano resonated, ultrathin, flexible and ultrawideband absorption featured nano-metaatom structure with dispersion gap optimized for optical range applications

This article reports an Ultra wideband nano scale metamaterial absorber with ultrathin and flexible feature for visible spectrum applications. The absorber investigated for dispersion and Fano resonance characteristics to achieve metamaterial properties as well as independent of asymmetry of structure. Maximum visible spectrum wave interaction with the cascaded split nano square meta atom also ensured to achieve the absorption at highest percentage in numerical evaluation. The Finite Difference Time Domain (FDTD) method incorporated with CST microwave studio computational tool used for the entire analysis. Numerical analysis revealed that, on average 86.66% absorption achieved for 560 THz bandwidth peak absorption for the unit cell was 99.88% and the array shows 99.79%. Dispersion gap optimized based on mode 4 to incorporate all photons for phase and group velocity inside the nano metamaterial absorber. Furthermore, the Fano resonance wave to identify the high-quality factor at visible spectrum on nanostructure meta atom and direct-indirect visible wave trapped in the structure. The dispersion gap optimization and Fano resonance make the proposed cascaded split nano square meta atom a significant candidate for visible spectrum applications like solar energy harvesting, biochemical sensing, optical range application etc.

Flexible cerium-doped tungstate oxide/titanium dioxide nanocomposite for high-sensitivity energy conversion in optical applications

Flexible cerium-doped tungstate oxide/titanium dioxide nanocomposite for high-sensitivity energy conversion in optical applications

Chloramphenicol-infused N-vinyl-based soft contact lenses for therapeutic and optical applications

Chloramphenicol-infused N-vinyl-based soft contact lenses for therapeutic and optical applications

Surface modification unleashes light emitting applications of APbX3 perovskite nanocrystals.

Engineering the surface of metal halide perovskite nanocrystals (MHPNCs) is crucial for optimizing their optical properties, repairing surface defects, enhancing quantum yield, and ensuring long-term stability. These enhancements make surface-engineered MHPNCs ideal for applications in light-emitting devices (LEDs), displays, lasers, and photodetectors, contributing to energy efficiency. This article delves into an introduction to MHPNCs, their structure and types, particularly the ABX3 type (where A represents monovalent organic/inorganic cations, B represents divalent metal ions mainly Pb metal, and X represents halide ions), synthesis methods, unique optical properties, surface modification techniques using various agents (particularly inorganic molecules/materials, organic molecules, polymers, and biomolecules) to tune optical properties and applications in the aforementioned light-emitting technologies, challenges and opportunities, including advantages and disadvantages of surface-modified APbX3 MHPNCs, and a summary and future outlook. This article explores surface modification strategies to improve the optical performance of MHPNCs and aims to inspire advancements in light emitting applications. Importantly, the challenges and opportunities section of this article will illuminate the path to overcoming obstacles, providing invaluable insights for researchers in this field. This in-depth review explores the surface engineering of MHPNCs for light-emitting applications, highlighting their notable advantages and addressing ongoing challenges. By delving deep into various surface modification strategies, this article aims to revolutionize MHPNC-based light-emitting applications, setting a new benchmark in the field. This paves the way for revolutionary advancements, maximizing the capabilities of surface-engineered MHPNCs and heralding a transformative era in precise light-emitting research.

Comprehensive Investigation of Ti-Doped Sr3CoSb2O9 Triple Perovskite: Structural, Morphological, Optical, and Dielectric Characteristics

We report a comprehensive investigation of the doped Ti4+ and the pristine Sr3CoSb2O9 triple perovskite material. By conducting a solid-state reaction in the air at room pressure, a stabilized single orthorhombic Immm (SG 71) phase is obtained. For series samples Sr3CoSb2−xTixO9 (x = 0.0, 0.1, 0.3, 0.5), using Rietveld refinements of powdered x-ray patterns, we reach to the conclusion that the Ti4+ doping at B-site has considerable impact on its structural parameters. The microstructure of the series samples was studied using FESEM and associated with EDS mapping for compositional analysis. The optical characteristics studied via optical absorbance measurements indicate that with an increasing doping concentration of Ti4+, the optical bandgap increases for 0.1 sample and then decreases up to 1.50 eV for 0.5 sample. As a result, they can be considered potential candidates for technological applications like photocatalytic systems and solar cells due to their suitable bandgap values and optical absorption-related applications. The FTIR analysis aimed to examine the bond forms and vibrational modes of the synthesized samples. Moreover, the space charge polarization mechanism explains a detailed analysis of temperature-dependent dielectric properties in the 1 KHz-2 MHz frequency range. The dielectric loss behavior is described by the thermally activated relaxation process tailored by the Arrhenius law and characterized by doping Ti4+ ions into the material’s structure. The existence of Co in Co2+ and Co3+ oxidation states, while Sb3+ state is stabilized with doping confirmed by X-ray photoelectron spectroscopy research. The current study thereby advances our knowledge of how these materials’ structural, morphological, optical, and dielectric characteristics are related.

Lasing in an assembled array of silver nanocubes.

We demonstrate a surface lattice resonance (SLR)-based plasmonic nanolaser that leverages bulk production of colloidal nanoparticles and assembly on templates with single particle resolution. SLRs emerge from the hybridization of the plasmonic and photonic modes when nanoparticles are arranged into periodic arrays and this can provide feedback for stimulated emission. It has been shown that perfect arrays are not a strict prerequisite for producing lasing. Here, we propose using high-quality colloids instead. Silver colloidal nanocubes feature excellent plasmonic properties due to their single-crystal nature and low facet roughness. We use capillarity-assisted nanoparticle assembly to produce substrates featuring SLR and comprising single nanocubes. Combined with the laser dye pyrromethene-597, the nanocube array lases at 574 nm with <1.2 nm linewidth, <100 μJ cm-2 lasing threshold, and produces a beam with <1 mrad divergence, despite less-than-perfect arrangement. Such plasmonic nanolasers can be produced on a large-scale and integrated in point-of-care diagnostics, photonic integrated circuits, and optical communications applications.

Explore the physical properties of the synthesized UiO-66, Zn-BiOBr, and Zn-BiOBr/UiO-66 heterostructures for optical applications

The Zn-BiOBr/UiO-66 Heterostructures were prepared using a simple wet chemical method. Three heterostructures were prepared by varying the weight percentage of UiO-66 to Zn-BiOBr. The prepared materials' chemical compositions and phase structure were investigated using Fourier transform infrared (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Furthermore, the morphology was investigated via Field-emission scanning electron microscope (FE-SEM), energy dispersive X-ray (EDX), and elemental mapping techniques. The optical features were analyzed through UV–vis spectrophotometry. The bandgap energy was calculated using the Tauc equation and was found 4.24eV for UiO66 and 2.17eV for the ZnBiOBr composite. After combining the ZnBiOBr composite with the UiO66 material the bandgap energy of the composite decreased to 4.07, 3.94, and 3.75eV after doping 10, 20, and 30% UiO-66, respectively. Additionally, the refractive index of the Zn-BiOBr/UiO-66 heterostructure increases from 2.1520 for the UiO-66 composite to about 2.1929, 2.2254, and 2.2748 for 10, 20, and 30% UiO66. Moreover, an enhancement was observed for other optical parameters like electronegativity, metallization, and optical conductivity. Besides, the W-DD model was used to investigate the nonlinear optical parameters, which showed an improvement in the first- and third-order nonlinear optical susceptibility, and nonlinear refractive index values with increasing UiO-66 content in the composite matrix.