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1.
Sci Rep ; 14(1): 23409, 2024 Oct 08.
Article in English | MEDLINE | ID: mdl-39379441

ABSTRACT

The fascinating electronic applications attracted researchers to explore the field of nonlinear optical (NLO) materials. The slow evaporation of solvent technique (SEST) was employed to grow the 2-cyanopyridinium perchlorate (2-CPPC) NLO single crystals. The cell parameters of the grown 2-CPPC crystal are confirmed by the single crystal X-ray diffraction (SCXRD) study. The powder X-ray diffraction studies confirm the crystallinity of 2-CPPC crystals, and the peaks were indexed. The computation for the geometry optimization, HOMO-LUMO energy gap, global reactivity parameters, natural bond orbital (NBO) analysis, polarizability, and hyperpolarizability of the 2-CPPC molecule was done using B3LYP (6-311G basis set) functional of DFT method. The experimental FTIR and UV-Vis results of the 2-CPPC compound were compared with the simulated results. The second harmonic generation (SHG) study for the 2-CPPC crystal was employed using Kurtz-Perry powder technique. Single beam Z-scan technique using He-Ne laser is used to study the third-order NLO properties.

2.
J Biomed Opt ; 29(9): 093511, 2024 Sep.
Article in English | MEDLINE | ID: mdl-39364328

ABSTRACT

Significance: Label-free multimodal imaging methods that can provide complementary structural and chemical information from the same sample are critical for comprehensive tissue analyses. These methods are specifically needed to study the complex tumor-microenvironment where fibrillar collagen's architectural changes are associated with cancer progression. To address this need, we present a multimodal computational imaging method where mid-infrared spectral imaging (MIRSI) is employed with second harmonic generation (SHG) microscopy to identify fibrillar collagen in biological tissues. Aim: To demonstrate a multimodal approach where a morphology-specific contrast mechanism guides an MIRSI method to detect fibrillar collagen based on its chemical signatures. Approach: We trained a supervised machine learning (ML) model using SHG images as ground truth collagen labels to classify fibrillar collagen in biological tissues based on their mid-infrared hyperspectral images. Five human pancreatic tissue samples (sizes are in the order of millimeters) were imaged by both MIRSI and SHG microscopes. In total, 2.8 million MIRSI spectra were used to train a random forest (RF) model. The other 68 million spectra were used to validate the collagen images generated by the RF-MIRSI model in terms of collagen segmentation, orientation, and alignment. Results: Compared with the SHG ground truth, the generated RF-MIRSI collagen images achieved a high average boundary F -score (0.8 at 4-pixel thresholds) in the collagen distribution, high correlation (Pearson's R 0.82) in the collagen orientation, and similarly high correlation (Pearson's R 0.66) in the collagen alignment. Conclusions: We showed the potential of ML-aided label-free mid-infrared hyperspectral imaging for collagen fiber and tumor microenvironment analysis in tumor pathology samples.


Subject(s)
Fibrillar Collagens , Machine Learning , Humans , Fibrillar Collagens/chemistry , Spectrophotometry, Infrared/methods , Pancreas/diagnostic imaging , Pancreas/chemistry , Image Processing, Computer-Assisted/methods , Second Harmonic Generation Microscopy/methods , Pancreatic Neoplasms/diagnostic imaging , Pancreatic Neoplasms/chemistry , Multimodal Imaging/methods , Hyperspectral Imaging/methods
3.
Nano Lett ; 2024 Oct 02.
Article in English | MEDLINE | ID: mdl-39356872

ABSTRACT

Nonlinear optical materials of atomic thickness, such as non-centrosymmetric 2H transition metal dichalcogenide monolayers, have a second-order nonlinear susceptibility (χ(2)) whose intensity can be tuned by strain. However, whether χ(2) is enhanced or reduced by tensile strain is a subject of conflicting reports. Here, we grow high-quality MoSe2 monolayers under controlled biaxial strain created by two different substrates and study their linear and nonlinear optical responses with a combination of experimental and theoretical approaches. Up to a 15-fold overall enhancement in second-harmonic generation (SHG) intensity is observed from MoSe2 monolayers grown on SiO2 when compared to its value on a Si3N4 substrate. By considering an interference contribution from different dielectrics and their thicknesses, a factor of 2 enhancement of χ(2) was attributed to the biaxial strain: substrate interference and strain are independent handles to engineer the SHG strength of non-centrosymmetric 2D materials.

4.
Nano Lett ; 2024 Oct 02.
Article in English | MEDLINE | ID: mdl-39356567

ABSTRACT

We demonstrate all-optical modulation with a near-unity contrast of nonlinear light generation in a dielectric metasurface. We study third-harmonic generation from silicon Fano-resonant metasurfaces excited by femtosecond pulses at 1480 nm wavelength. We modulate the metasurface resonance by free carrier excitation induced by absorption of an 800 nm pump pulse, leading to up to 93% suppression of third-harmonic generation. Modulation and recovery occur on (sub)picosecond time scales. According to the Drude model, the pump-induced refractive index change blue-shifts the metasurface resonance away from the generation pulse, causing a strong modulation of third-harmonic conversion efficiency. The principle holds great promise for spatiotemporal programmability of nonlinear light generation.

5.
Angew Chem Int Ed Engl ; : e202415318, 2024 Sep 21.
Article in English | MEDLINE | ID: mdl-39305146

ABSTRACT

AgGaS2 (AGS) is the most commonly used commercial infrared nonlinear optical material. However, AGS has a narrow band gap (Eg = 2.58 eV) and a low laser-induced damage threshold (LIDT), primarily attributed to its mobile liquid-like Ag+ constituent and the unstable Ag-S chemical bond. Herein, we propose a "band reformation of AGS" strategy, which leads to the success syntheses of four lanthanide sulfides, LiLnGeS4, crystalizing in an asymmetric Ama2 structure. LiLaGeS4 demonstrates that eliminating the presence of Ag-4d band increases the Eg to 3.32 eV and enhances the LIDT (14-29 × AGS, measured by both powder and single crystal); while increasing the nonbonding density of states of the S-3p band enhances the 2nd-nonlinear optical coefficient (1.06 × AGS). Besides, the bond length discrepancy between [LiS4], [GeS4] and [LaS8] units leads to a moderate birefringence (Δn = 0.052). Such a unique structure further results in extremely small thermal expansion with αL = 0.41-1.74 × 10-5 K-1, along different crystallographic axes. Our theoretical studies indicate that the synergy of the structure building units contribute to the second harmonic generation performance. These results suggest that the "band reformation of AGS" strategy provides effective guidance to discover new NLO crystals with optimized performance.

6.
Micromachines (Basel) ; 15(9)2024 Sep 12.
Article in English | MEDLINE | ID: mdl-39337805

ABSTRACT

Frequency conversion process based on periodically poled thin-film lithium niobate (PPTFLN) has been widely recognized as an important component for quantum information and photonic signal processing. Benefiting from the tight confinement of optical modes, the normalized conversion efficiency (NCE) of nanophotonic waveguides is improved by orders of magnitude compared to their bulk counterparts. However, the power conversion efficiency of these devices is limited by inherent nanoscale inhomogeneity of thin-film lithium niobate (TFLN), leading to undesirable phase errors. In this paper, we theoretically present a novel approach to solve this problem. Based on dispersion engineering, we aim at adjusting the waveguide structure, making local waveguide width adjustment at positions of different thicknesses, thus eliminating the phase errors. The adapted waveguide width design is applied for etched and loaded waveguides based on PPTFLN, achieving the ultrahigh power conversion efficiency of second harmonic generation (SHG) up to 2.1 × 104%W-1 and 6936%W-1, respectively, which surpasses the power conversion efficiency of other related works. Our approach just needs standard periodic poling with a single period, significantly reducing the complexity of electrode fabrication and the difficulty of poling, and allows for the placing of multiple waveguides, without individual poling designs for each waveguide. With the advantages of simplicity, high production, and meeting current micro-nano fabrication technology, our work may open a new way for achieving highly efficient second-order nonlinear optical processes based on PPTFLN.

7.
Liver Int ; 2024 Sep 09.
Article in English | MEDLINE | ID: mdl-39248039

ABSTRACT

BACKGROUND AND AIMS: Metabolic dysfunction-associated steatohepatitis (MASH) with bridging fibrosis is a critical stage in the evolution of fatty liver disease. Second harmonic generation/two-photon excitation fluorescence (SHG/TPEF) microscopy with artificial intelligence (AI) provides sensitive and reproducible quantitation of liver fibrosis. This methodology was applied to gain an in-depth understanding of intra-stage fibrosis changes and septa analyses in a homogenous, well-characterised group with MASH F3 fibrosis. METHODS: Paired liver biopsies (baseline [BL] and end of treatment [EOT]) of 57 patients (placebo, n = 17 and tropifexor n = 40), with F3 fibrosis stage at BL according to the clinical research network (CRN) scoring, were included. Unstained sections were examined using SHG/TPEF microscopy with AI. Changes in liver fibrosis overall and in five areas of liver lobules were quantitatively assessed by qFibrosis. Progressive, regressive septa, and 12 septa parameters were quantitatively analysed. RESULTS: qFibrosis demonstrated fibrosis progression or regression in 14/17 (82%) patients receiving placebo, while the CRN scoring categorised 11/17 (65%) as 'no change'. Radar maps with qFibrosis readouts visualised quantitative fibrosis dynamics in different areas of liver lobules even in cases categorised as 'No Change'. Measurement of septa parameters objectively differentiated regressive and progressive septa (p < .001). Quantitative changes in individual septa parameters (BL to EOT) were observed both in the 'no change' and the 'regression' subgroups, as defined by the CRN scoring. CONCLUSION: SHG/TPEF microscopy with AI provides greater granularity and precision in assessing fibrosis dynamics in patients with bridging fibrosis, thus advancing knowledge development of fibrosis evolution in natural history and in clinical trials.

8.
Angew Chem Int Ed Engl ; : e202416856, 2024 Sep 18.
Article in English | MEDLINE | ID: mdl-39291894

ABSTRACT

Flexible crystals with unique mechanical properties have presented enormous applications in optoelectronics, soft robotics and sensors. However, there have been no reports of low-temperature-resistant flexible crystals with second-order nonlinear optical properties (NLO). Here, we report the flexible chiral Schiff-base crystals capable of efficient second harmonic generation (SHG). Both enantiomers and racemic modifications of these crystals are mechanically flexible in two directions at both room temperature and at -196 °C, although their mechanical responses differ. The enantiomers display SHG with an intensity of up to 12 times that of potassium dihydrogenphosphate (KDP) when pumped at 980 nm, and they also have high laser-induced damage thresholds (LDT). Even when bent, the crystals retain strong second harmonic generation, although with a different intensity distribution depending on the polarization, compared to when they are straight. This work describes the first instance of flexible organic crystal with NLO properties and lays the foundation for the development of mechanically flexible organic NLO materials.

9.
Nano Lett ; 24(37): 11676-11682, 2024 Sep 18.
Article in English | MEDLINE | ID: mdl-39225551

ABSTRACT

Second-order nonlinearity gives rise to many distinctive physical phenomena, e.g., second-harmonic generation, which play an important role in fundamental science and various applications. Lithium niobate, one of the most widely used nonlinear crystals, exhibits strong second-order nonlinear effects and electro-optic properties. However, its moderate refractive index and etching sidewall angle limit its capability in confining light into nanoscales, thereby restricting its application in nanophotonics. Here, we exploit nanocavities formed by second-order circular Bragg gratings, which support resonant anapole modes, to achieve a 42 000-fold enhanced second-harmonic generation in thin-film lithium niobate. The nanocavity exhibits a record-high normalized conversion efficiency of 1.21 × 10-2 cm2/GW under the pump intensity of 1.9 MW/cm2. Besides, we also show s- and p-polarization-independent second-harmonic generation in elliptical Bragg nanocavities. This work could inspire the study of nonlinear optics at the nanoscale on thin-film lithium niobate, as well as other novel photonic platforms.

10.
ACS Infect Dis ; 10(9): 3233-3244, 2024 Sep 13.
Article in English | MEDLINE | ID: mdl-39178142

ABSTRACT

Depending upon nutrient availability, bacteria transit to multiple growth phases. The transition from the active to nongrowing phase results in reduced drug efficacy and, in some cases, even multidrug resistance. However, due to multiple alterations in the cell envelope, probing the drug permeation kinetics during growth phases becomes perplexing, especially across the Gram-negative bacteria's complex dual membrane envelope. To advance the understanding of drug permeation during the life cycle of Gram-negative bacteria, we sought to address two underlying objectives: (a) how changes are occurring inside the bacterial envelope during growth and (b) how the drug permeation and accumulation vary across both the membranes and in subcellular compartments during growth. Both objectives are met with the help of nonlinear optical technique second-harmonic generation spectroscopy (SHG). Specifically, using SHG, we probed the transport kinetics and accumulation of a quaternary ammonium compound (QAC), malachite green, inside Escherichia coli in various growth phases. Further insight about another QAC molecule, propidium iodide, is accomplished using fluorescence microscopy. Results indicate that actively growing cells have faster drug transport and higher cytoplasmic accumulation than slow- or nongrowing cells. In this regard, the rpoS gene plays a crucial role in limiting drug transport across the saturation phase cultures. Moreover, within a particular growth phase, membrane permeability undergoes gradual changes much before the subsequent growth phase commences. These outcomes signify the importance of reporting the growth phase and rate in drug efficacy studies.


Subject(s)
Escherichia coli , Escherichia coli/metabolism , Escherichia coli/growth & development , Escherichia coli/genetics , Biological Transport , Anti-Bacterial Agents/pharmacology , Cell Membrane/metabolism , Propidium/metabolism , Kinetics
11.
Nano Lett ; 24(36): 11327-11333, 2024 Sep 11.
Article in English | MEDLINE | ID: mdl-39197173

ABSTRACT

Integrated photonic microcavities have demonstrated powerful enhancement of nonlinear effects, but they face a challenge in achieving critical coupling for sufficient use of incident pump power. In this work, we first experimentally demonstrate that highly efficient third-harmonic generation (THG) and detectable second-harmonic generation (SHG) can be produced from high-Q photonic moiré superlattice microcavities, where a critical coupling condition can be achieved via selecting a magic angle. Furthermore, at the magic angle of 13.17°, critical coupling is satisfied, resulting in a normalized THG conversion efficiency of 136%/W2 at a relatively low peak pump power of 6.8 MW/cm2, which is 3 orders of magnitude higher than the best results reported previously. Our work shows the power of photonic moiré superlattices in enhancing nonlinear optical performances through flexible and feasible engineering resonant modes, which can be applied in integrated frequency conversion and generation of quantum light sources.

12.
J Pediatr Gastroenterol Nutr ; 79(4): 818-825, 2024 Oct.
Article in English | MEDLINE | ID: mdl-39129391

ABSTRACT

BACKGROUND: In patients with biliary atresia (BA), severe portal hypertension (HTN) develops even with successful bile flow restoration, suggesting an intrinsic factor driving portal HTN independent from bile obstruction. We hypothesize that patients with BA have abnormal portal vein (PV) development, leading to PV hypoplasia. METHODS: In this observational cohort study, we enrolled patients who were referred to a tertiary center from 2017 to 2021 to rule out BA. Newborns who underwent computed tomography angiogram as a clinical routine before intraoperative cholangiogram, and laparoscopic Kasai hepatoportoenterostomy. The diameter of the PV and hepatic artery (HA) were compared to the degree of liver fibrosis in the wedge biopsies. The jaundice clearance, native liver survival, and clinical portal hypertensive events, including ascites development and intestinal bleeding, were assessed. RESULTS: 47 newborns with cholestasis were included in the cohort; 35 were diagnosed with BA. The patients with BA had a smaller median PV diameter (4.3 vs. 5.1 mm; p < 0.001) and larger median HA diameter (1.4 vs. 1.2 mm; p < 0.05) compared to the patients with other forms of cholestasis. The median PV and HA diameter did not correlate with the degree of liver fibrosis. Among 35 patients with BA, 29 patients (82.9%) achieved jaundice clearance, and 23 patients (65.7%) were alive with their native liver at two years of age. Seven patients (20%) developed intestinal bleeding, and seven patients (20%) developed ascites, with one overlapping patient. CONCLUSION: PV hypoplasia is present in patients with BA independent of liver fibrosis at the time of diagnosis.


Subject(s)
Biliary Atresia , Hypertension, Portal , Portal Vein , Humans , Biliary Atresia/complications , Biliary Atresia/surgery , Biliary Atresia/diagnosis , Portal Vein/abnormalities , Portal Vein/diagnostic imaging , Portal Vein/pathology , Female , Male , Infant, Newborn , Hypertension, Portal/etiology , Hypertension, Portal/diagnosis , Hypertension, Portal/complications , Portoenterostomy, Hepatic , Cohort Studies , Infant , Liver Cirrhosis/complications , Liver Cirrhosis/diagnosis
13.
Adv Mater ; 36(40): e2407249, 2024 Oct.
Article in English | MEDLINE | ID: mdl-39194637

ABSTRACT

The realization of spontaneous ferroelectricity down to the one-dimensional (1D) limit is both fundamentally intriguing and practically appealing for high-density ferroelectric and nonlinear photonics. However, the 1D vdW ferroelectric materials are not discovered experimentally yet. Here, the first 1D vdW ferroelectric compound NbOI3 with a high Curie temperature TC > 450 K and giant second harmonic generation (SHG) is reported. The 1D crystalline chain structure of the NbOI3 is revealed by cryo-electron microscopy, whereas the 1D ferroelectric order originated from the Nb displacement along the Nb-O chain (b-axis) is confirmed via obvious electrical and ferroelectric hysteresis loops. Impressively, NbOI3 exhibits a giant SHG susceptibility up to 1572 pm V-1 at a fundamental wavelength of 810 nm, and a further enhanced SHG susceptibility of 5582 pm V-1 under the applied hydrostatic pressure of 2.06 GPa. Combing in situ pressure-dependent X-ray diffraction, Raman spectra measurements, and first-principles calculations, it is demonstrated that the O atoms shift along the Nb─O atomic chain under compression, which can lead to the increased Baur distortion of [NbO2I4] octahedra, and hence induces the enhancement of SHG. This work provides a 1D vdW ferroelectric system for developing novel ferroelectronic and photonic devices.

14.
Acta Biomater ; 187: 227-241, 2024 Oct 01.
Article in English | MEDLINE | ID: mdl-39209134

ABSTRACT

Collagen fiber architecture within the skeletal muscle extracellular matrix (ECM) is significant to passive muscle mechanics. While it is thought that collagen fibers re-orient themselves in response to changes in muscle length, this has not been dynamically visualized and quantified within a muscle. The goal of this study was to measure changes in collagen alignment across a range of muscle lengths and compare the corresponding alignment to muscle mechanics. We hypothesized that collagen fibers dynamically increase alignment in response to muscle stretching, and this change in alignment is related to passive muscle stiffness. Further, we hypothesized that digesting collagen fibers with collagenase would reduce the re-alignment response to muscle stretching. Using DBA/2J and D2.mdx mice, we isolated extensor digitorum longus (EDL), soleus, and diaphragm muscles for collagenase or sham treatment and decellularization to isolate intact or collagenase-digested decellularized muscles (DCMs). These DCMs were mechanically tested and imaged using second harmonic generation microscopy to measure collagen alignment across a range of strains. We found that collagen alignment increased in a strain-dependent fashion, but collagenase did not significantly affect the strain-dependent change in alignment. We also saw that the collagen fibers in the diaphragm epimysium (surface ECM) and perimysium (deep ECM) started at different angles, but still re-oriented in the same direction in response to stretching. These robust changes in collagen alignment were weakly related to passive DCM stiffness. Overall, we demonstrated that the architecture of muscle ECM is dynamic in response to strain and is related to passive muscle mechanics. STATEMENT OF SIGNIFICANCE: Our study presents a unique visualization and quantification of strain-induced changes in muscle collagen fiber alignment as they relate to passive mechanics. Using dynamic imaging of collagen in skeletal muscle we demonstrate that as skeletal muscle is stretched, collagen fibers re-orient themselves along the axis of stretch and increase their alignment. The degree of alignment and the increase in alignment are each weakly related to passive muscle stiffness. Collagenase treatments further demonstrate that the basis for muscle Extracellular matrix stiffness is dependent on factors beyond collagen crosslinking and alignment. Together the study contributes to the knowledge of the structure-function relationships of muscle extracellular matrix to tissue stiffness relevant to conditions of fibrosis and aberrant stiffness.


Subject(s)
Collagen , Extracellular Matrix , Muscle, Skeletal , Animals , Extracellular Matrix/metabolism , Muscle, Skeletal/metabolism , Mice , Collagen/metabolism , Mice, Inbred DBA , Collagenases/metabolism , Stress, Mechanical , Male
15.
ACS Nano ; 18(33): 21939-21947, 2024 Aug 20.
Article in English | MEDLINE | ID: mdl-39115247

ABSTRACT

In moiré crystals resulting from the stacking of twisted two-dimensional (2D) layered materials, a subtle adjustment in the twist angle surprisingly gives rise to a wide range of correlated optical and electrical properties. Herein, we report the synthesis of supertwisted WS2 spirals and the observation of giant second harmonic generation (SHG) in these spirals. Supertwisted WS2 spirals featuring different twist angles are synthesized on a Euclidean or step-edge particle-induced non-Euclidean surface using carefully designed water-assisted chemical vapor deposition. We observed an oscillatory dependence of SHG intensity on layer number, attributed to atomically phase-matched nonlinear dipoles within layers of supertwisted spiral crystals where inversion symmetry is restored. Through an investigation into the twist angle evolution of SHG intensity, we discovered that the stacking model between layers plays a crucial role in determining the nonlinearity, and the SHG signals in supertwisted spirals exhibit enhancements by a factor of 2 to 136 when compared with the SHG of the single-layer structure. These findings provide helpful perspectives on the rational growth of 2D twisted structures and the implementation of twist angle adjustable endowing them great potential for exploring strong coupling correlation physics and applications in the field of twistronics.

16.
Angew Chem Int Ed Engl ; : e202413276, 2024 Aug 12.
Article in English | MEDLINE | ID: mdl-39132935

ABSTRACT

In the deep-ultraviolet (DUV) region, nonlinear optical (NLO) crystals must meet stringent requirements, including a large optical band gap and sufficient second harmonic generation (SHG) response. Typically, these criteria are fulfilled by borates, carbonates and nitrates containing π-conjugated groups. In contrast, sulfates and phosphates, with polarizabilities significantly smaller than those of π-conjugated groups, struggle to achieve similar performance. Here, we present the discovery of Mg2PO4Cl, a magnesium-based phosphate, identified from over 10,000 phosphates based on a polar-axial-symmetry screening strategy, which exhibits the highest SHG response (5.2 × KH2PO4 (KDP)) with phase-matching ability among non-π-conjugated DUV transparent NLO crystals. This compound belongs to the Pna21 space group, with [PO4] units consistently aligned along the 21 screw axis and glide planes throughout its crystal structure. Theoretical calculations attribute its remarkable SHG effect to the orderly arrangement of heteroanionic [MgO5Cl] and [MgO4Cl2] polyhedra alongside isolated [PO4] tetrahedra, supported by Berry phase analysis. Furthermore, a crystallographic structure analysis of phosphates and sulfates with significant SHG effects validates the effectiveness of our screening strategy. These findings offer valuable insights into the origins of NLO effects in non-π-conjugated compounds from both a material design and structural chemistry perspective, inspiring future efforts to revitalize DUV phosphates.

17.
Adv Sci (Weinh) ; : e2408329, 2024 Aug 29.
Article in English | MEDLINE | ID: mdl-39206774

ABSTRACT

The discovery of polar metal opens the door to incorporating electric polarization into electronics with the potential to invigorate next-generation multifunctional electronic devices. Especially, electric polarization can be induced by geometric design in non-polar perovskite oxides. Here, the epitaxial strain exerted on the deposited single-crystalline NdNiO3 thin films is systematically varied in both sign and amplitude by choosing substrates with different lattice mismatch. The pseudocubic NdNiO3(111) film, which is non-polar in its bulk state, is induced to be polar under both compressive and tensile strain. The fine-tuning of epitaxial strain is realized by continuously varying the film thickness using the "thickness-wedge" growth technique, and from the elucidated thickness dependence, the electric polarization and metallicity can be further optimized. Moreover, transitioning from isotropic to anisotropic epitaxial strain gives rise to an ideal polar metal state in the pseudocubic NdNiO3(102) film on an orthorhombic substrate, achieving a remarkably low resistivity of 173 µΩ cm at room temperature. The metal-insulator transition in NdNiO3 is completely suppressed and the polar metal state becomes the ground state at all temperatures. These results demonstrate alluring possibilities of induction and manipulation of both electric polarization and electric transport properties in functional perovskite oxides by epitaxial strain engineering.

18.
Int J Mol Sci ; 25(15)2024 Jul 25.
Article in English | MEDLINE | ID: mdl-39125674

ABSTRACT

The molecular laser-induced plasma (LIP) produced during the ablation of silver sulfide (Ag2S) was used as a medium for high-order harmonic generation in the extreme ultraviolet range. The role of LIP formation, the plasma components, and the geometry of plasma in the harmonic conversion efficiency was analyzed. We also analyzed the influence of the driving pulses (chirp, single-color pump, two-color pump, and delay between heating and converting pulses) on the harmonic yield in Ag2S LIP. The application of molecular plasma was compared with the application of atomic plasma, which comprised similar metallic elements (Ag) as well as other metal LIPs. The harmonics from the Ag2S LIP were 4 to 10 times stronger than those from the Ag LIP. The harmonics up to the 59th order were achieved under the optimal conditions for the molecular plasma.


Subject(s)
Plasma Gases , Silver Compounds , Silver Compounds/chemistry , Lasers
19.
Nano Lett ; 24(34): 10577-10582, 2024 Aug 28.
Article in English | MEDLINE | ID: mdl-39150721

ABSTRACT

Nonlinear chiral photonics explores the nonlinear response of chiral structures, and it offers a pathway to novel optical functionalities not accessible through linear or achiral systems. Here we present the first application of nanostructured van der Waals materials to nonlinear chiral photonics. We demonstrate the 3 orders of magnitude enhancement of the third-harmonic generation from hBN metasurfaces driven by quasi-bound states in the continuum and accompanied by strong nonlinear circular dichroism at the resonances. This novel platform for chiral metaphotonics can be employed for achieving large circular dichroism combined with high-efficiency harmonic generation in a broad frequency range.

20.
ACS Nano ; 18(34): 22978-22988, 2024 Aug 27.
Article in English | MEDLINE | ID: mdl-39136625

ABSTRACT

Two-dimensional (2D) materials provide a versatile platform for the integration of diverse crystals, enabling the formation of heterostructures with intriguing functionalities. Coherently growing 2D heterostructures are highly desirable for property manipulation due to their strong interfacial interaction. In this work, we propose a general synthesis approach and provide insight into well-designed 2D binary-ternary magnetic heterostructures. Atomically sharp interfaces were achieved in typical lateral and vertical Cr1+mSe2(001)/CuCr2Se4(111) heterostructures owing to their similar lattice arrangement, with the observation of a significant enhancement of optical second-harmonic generation. Further magnetism measurements revealed a Curie temperature up to 360 K and thickness- and temperature-dependent magnetism in this heterostructure. Additionally, we synthesized three analogous 2D magnetic heterostructures in Fe-Cr-S, Co-Cr-S, and Cu-Cr-S systems, demonstrating the ubiquitous nature of the coherent heteroepitaxy. Our work involves the development of an innovative platform for investigating the underlying physics and potential applications of 2D binary-ternary heterostructures as well as the fabrication of associated functional devices.

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