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Enhanced second harmonic generation of Hermitea??Gaussian laser beam in plasma having density transition
摘要： Under the combined effect of relativistic and ponderomotive nonlinearity, resonant second harmonic generation of an intense Hermite–Gaussian (H–Gaussian) laser beam in a plasma having upward density ramp profile has been theoretically investigated. Under WKB approximation and with the use of the moment theory approach the coupled differential equations are derived which govern the spot size of the H–Gaussian laser beam. The ponderomotive force creates the density gradient in the background plasma electrons which is responsible for the excitation of the electron plasma wave. The large-amplitude electron plasma wave interacts with the fundamental beam which produces coherent radiations with double the frequency of the incident beam. In addition, the Gouy phase shift is observed for the H–Gaussian laser beam in plasma under the effect of density transition. The analysis shows the vital role of the different modes of the H–Gaussian laser beam and density ramp on the efficiency of generated harmonics and self-phase shift of laser beams in plasma.
关键词： ponderomotive,density ramp,second harmonic generation,relativistic nonlinearity,Hermite–Gaussian laser beam
更新于2025-09-19 17:13:59
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Structure and property relationship of methoxy substituted novel organic crystals for photonic applications
摘要： In the present work, a promising non-centrosymmetric chalcone derivative 3-(2, 4, 6-trimethoxyphenyl)-1-(thiophen-2-yl)-prop-2-en-1-one (2TM) was investigated to define their potential for photonic applications through various characterization techniques. Therefore 2TM has been synthesized and single crystals have been grown using slow evaporation solution growth technique. The UV–Vis-NIR spectrum reveals the transparency of the crystal for the entire visible region. The thermal stability and phase transition of the compound was studied by thermo gravimetric and differential thermal analysis and found to be stable up to 132 °C. For structural conformation, the Fourier transform infrared spectral tests were performed on 2TM. For nonlinear optical studies of the third order, the Z-scan experiment was conducted. The material had reverse saturation absorption and self-defocusing properties and therefore, 2TM showed strong nonlinear absorption coefficients and optical limiting behavior, under continuous wave diode-pumped solid state laser. Second harmonic generation efficiency of 2TM crystal is 1.12 times the urea efficiency. The single crystal x-ray diffraction studies of the crystal showed that the crystal system of 2TM is orthorhombic with space group P n a 21. The structural and property relationship studies are carried out for the methoxy substituted organic crystals. Thus, the reported crystal can be used for photonic applications due to its excellent optical properties.
关键词： Single crystal,Chalcones,Z-scan,Second harmonic generation,Structure–property relationship
更新于2025-09-19 17:13:59
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LiBa <sub/>4</sub> Ga <sub/>5</sub> Q <sub/>12</sub> (Q = S, Se): Noncentrosymmetric Metal Chalcogenides with a Cesium Chloride Topological Structure Displaying a Remarkable Laser Damage Threshold
摘要： The exploration of novel infrared nonlinear optical (IR NLO) materials with large second-harmonic generation (SHG) responses and wide band gaps has become very imperative recently. Herein we reported two noncentrosymmetric compounds, LiBa4Ga5Q12 (Q = S, Se), crystallizing in space group P421c (No. 114), which feature 3D frameworks built by a basic [Ga5Q16]17? windmill cluster and LiQ4 tetrahedra in a cesium chloride topological structure. Both compounds satisfy the desired balance between good SHG responses (～1.5× that of AgGaS2) and wide band gaps (3.43 and 2.44 eV) with remarkable laser damage thresholds (21× and 6× that of AgGaS2). The theoretical calculations uncover that the [Ga5Q16]17? cluster makes major contributions to the SHG e?ect in LiBa4Ga5Q12. In addition, the structure?performance relationship among all compounds in the I?II4?III5?VI12 system has been discussed systematically, which indicates that the introduction of the alkali metal lithium in the I site is bene?cial for the production of large band gaps. This work will be helpful in exploring novel IR NLO materials with special structures and comprehensive properties in the chalcogenide system.
关键词： chalcogenides,infrared nonlinear optical materials,laser damage thresholds,cesium chloride topological structure,second-harmonic generation
更新于2025-09-19 17:13:59
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Plasmon enhanced second harmonic generation by periodic arrays of triangular nanoholes coupled to quantum emitters
摘要： Optical properties of periodic arrays of nanoholes of a triangular shape with experimentally realizable parameters are examined in both linear and nonlinear regimes. By utilizing a fully vectorial three-dimensional approach based on the nonlinear hydrodynamic Drude model describing metal coupled to Maxwell’s equations and Bloch equations for molecular emitters, we analyze linear transmission, reflection, and nonlinear power spectra. Rigorous numerical calculations demonstrating second and third harmonic generation by the triangular hole arrays are performed. It is shown that both the Coulomb interaction of conduction electrons and the convective term contribute on equal footing to the nonlinear response of metal. It is demonstrated that the energy conversion efficiency in the second harmonic process is the highest when the system is pumped at the localized surface plasmon resonance. When molecular emitters are placed on a surface of the hole array line shapes, the second harmonic signal exhibits three peaks corresponding to second harmonics of the localized surface plasmon mode and upper and lower polaritonic states.
关键词： strong coupling,second harmonic generation,hydrodynamic Drude model,plasmonics,nonlinear optics
更新于2025-09-19 17:13:59
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All-Dielectric Nanoresonators for ??(2) Nonlinear Optics
摘要： Metal-less nanophotonics offers new opportunities for non-linear optics with respect to optical waveguides and microresonators, taking advantage of the progress within nanofabrication to boost the development of subwavelength Mie-type structures. Here, we review recent results on second harmonic generation with semiconductor nanoresonators, focusing on their scattering features in terms of efficiency and control over radiation patterns. First, two theoretical models are comparatively discussed with a view to possible improvements in analysis and design. Then, some relevant experiments are reported, and the origin of the χ(2) generation is discussed, outlining the main open topics to investigate in the near future and the advantages offered by these nanostructures to the development of novel photonic devices.
关键词： Mie resonances,second harmonic generation,AlGaAs nanoresonators,all-dielectric resonators,nanophotonics
更新于2025-09-19 17:13:59
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Chiral Second-Harmonic Generation from Monolayer WS <sub/>2</sub> /Aluminum Plasmonic Vortex Metalens
摘要： Two-dimensional spiral plasmonic structures have emerged as a versatile approach to generate near-field vortex fields with tunable topological charges. We demonstrate here a far-field approach to observe the chiral second-harmonic generation (SHG) at designated visible wavelengths from a single plasmonic vortex metalens. This metalens comprises an Archimedean spiral slit fabricated on atomically flat aluminum epitaxial film, which allows for precise tuning of plasmonic resonances and subsequent transfer of two-dimensional materials on top of the spiral slit. The nonlinear optical measurements show a giant SHG circular dichroism. Furthermore, we have achieved an enhanced chiral SHG conversion efficiency (about an order of magnitude greater than the bare aluminum lens) from monolayer tungsten disulfide (WS2)/aluminum metalens, which is designed at the C-exciton resonance of WS2. Since the C-exciton is not a valley exciton, the enhanced chiral SHG in this hybrid system originates from the plasmonic vortex field-enhanced SHG under the optical spin-orbit interaction.
关键词： optical spin-orbit interaction,Surface plasmonic vortex metalens,aluminum epitaxial film,chiral nonlinearity,second-harmonic generation,monolayer tungsten disulfide
更新于2025-09-19 17:13:59
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Cover Feature: Functional Metal Oxides in Perovskite Solar Cells (ChemPhysChem 20/2019)
摘要： The conflict between beneficial layered structure for performances and layered growth habits in KBe2BO3F2 (KBBF) always restricts its practical applications. A beryllium-free KBBF family member, Zn2BO3(OH), is explored to feature the same topological layer with KBBF by replacing [BeO3F]5? with [ZnO3(OH)]5? and excellent UV performances. It exhibits a second harmonic generation response of about 1.5 × KH2PO4 with the UV cutoff edge of 204 nm. The birefringence of Zn2BO3(OH) in the visible region is about 0.067, which is larger than those of commercial UV crystals LiB3O5, CsB3O5, and CsLiB6O10. Additionally, it has excellent thermal and water-resistant stabilities. Owing to the removal of interlayer cations, Zn2BO3(OH) shows better growth habits than KBBF while achieving the balance between beneficial layered structure and layer tendency.
关键词： borates,KBBF family,second harmonic generation,nonlinear optical materials,crystal growth habits
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Sub-20 fs ? 10.5 W Visible Pulse Generation from Yb-Doped Fiber Laser
摘要： High-power high-repetition rate femtosecond ytterbium-doped fiber lasers offer new perspectives in femtochemistry, solid-state physics and strong field physics. In particular, high-order harmonic generation (HHG) driven by Yb-fiber laser has demonstrated high photons flux in extreme ultraviolet (XUV) spectral range [1,2]. Shortening the laser pulse improves the achievable time resolution in pump-probe experiments and also the efficiency and the spectral extent of HHG (cutoff wavelength). However, the gain bandwidth of the Yb:fiber limits the pulse duration in the 250 fs - 130 fs range. To solve this issue, nonlinear pulse compression experiments using Yb:fiber lasers have been carried out at the fundamental wavelength (1030 nm) to downscale the pulse duration in the 10 fs range [3,4]. On the other hand, so far the highest reported XUV photons flux up to milliwatt-class has been obtained at 515 nm driving wavelength with 11W - 85 fs pulses [5]. While frequency doubling an ultrashort (< 30 fs) pulse requires a trade-off between efficiency and pulse duration lengthening, we present in this work an efficient and high power sub-20 fs visible laser source based on the second harmonic generation (SHG) of a high energy Yb-doped femtosecond fiber laser followed by a nonlinear compression stage in a krypton-filled capillary.
关键词： femtosecond ytterbium-doped fiber lasers,nonlinear pulse compression,krypton-filled capillary,second harmonic generation,high-order harmonic generation
更新于2025-09-16 10:30:52
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Second Harmonic Generation for Moisture Monitoring in Dimethoxyethane at a Gold-Solvent Interface Using Plasmonic Structures
摘要： Second harmonic generation (SHG) is forbidden from most bulk metals because metals are characterized by centrosymmetric symmetry. Adsorption or desorption of molecules at the metal interface can break the symmetry and lead to SHG responses. Yet, the response is relatively low, and minute changes occurring at the interface, especially at solid/liquid interfaces, like in battery electrodes are difficult to assess. Herein, we use a plasmonic structure milled in a gold electrode to increase the overall SHG signal from the interface and gain information about small changes occurring at the interface. Using a specific homebuilt cell, we monitor changes at the liquid/electrode interface. Specifically, traces of water in dimethoxyethane (DME) have been detected following changes in the SHG responses from the plasmonic structures. We propose that by plasmonic structures this technique can be used for assessing minute changes occurring at solid/liquid interfaces such as battery electrodes.
关键词： second-order nonlinear susceptibility,second harmonic generation (SHG),plasmonic enhancement,battery
更新于2025-09-16 10:30:52
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Single-Pass Laser Frequency Conversion to 780.2 nm and 852.3 nm Based on PPMgO:LN Bulk Crystals and Diode-Laser-Seeded Fiber Amplifiers
摘要： We report the preparation of a 780.2 nm and 852.3 nm laser device based on single-pass periodically poled magnesium-oxide-doped lithium niobate (PPMgO:LN) bulk crystals and diode-laser-seeded fiber amplifiers. First, a single-frequency continuously tunable 780.2 nm laser of more than 600 mW from second-harmonic generation (SHG) by a 1560.5 nm laser can be achieved. Then, a 250 mW light at 852.3 nm is generated and achieves an overall conversion efficiency of 4.1% from sum-frequency generation (SFG) by mixing the 1560.5 nm and 1878.0 nm lasers. The continuously tunable range of 780.2 nm and 852.3 nm are at least 6.8 GHz and 9.2 GHz. By employing this laser system, we can conveniently perform laser cooling, trapping and manipulating both rubidium (Rb) and cesium (Cs) atoms simultaneously. This system has promising applications in a cold atoms Rb-Cs two-component interferemeter and in the formation of the RbCs dimer by the photoassociation of cold Rb and Cs atoms confined in a magneto-optical trap.
关键词： single-pass sum-frequency generation,fiber amplifier,rubidium D2 line (780.2 nm),single-pass second-harmonic generation,cesium D2 line (852.3 nm)
更新于2025-09-16 10:30:52