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Some structural, linear and nonlinear optical characteristics of single KDP crystals influenced by EDTA additive
摘要： Single Potassium Dihydrogen Phosphates (KDP) crystals were successfully grown in pure and 1 mol% Ethylenediaminetetraacetic acid disodium salt (EDTA) added KDP solutions by Sankaranarayanan–Ramasamy method. Their growth was oriented in type I phase-matching direction which is one of two conditions of maximum second harmonic generation efficiency. The elemental compositions of the crystals were determined by EDX analysis. The UV–Vis spectroscopy, FT-IR analysis, X-Ray diffraction, and second harmonic generation studies have been carried out in order to assess the influence of EDTA additive on quality of KDP crystal. EDTA can improve the structural perfection and optical characteristics of the crystal. Especially, this additive helps increase second harmonic generation efficiency of KDP crystal, which is very useful for frequency doublers.
关键词： Second harmonic generation,EDTA,KDP,Nonlinear optics,SR method
更新于2025-09-23 15:21:21
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Ferroelectric Polarization Rotation in Order-Disorder-Type LiNbO3 Thin Films
摘要： The direction of ferroelectric polarization is prescribed by the symmetry of the crystal structure. Therefore, rotation of the polarization direction is largely limited, despite the opportunity it offers in understanding important dielectric phenomena such as piezoelectric response near the morphotropic phase boundaries and practical applications such as ferroelectric memory. In this study, we report the observation of continuous rotation of ferroelectric polarization in order-disorder-type LiNbO3 thin films. The spontaneous polarization could be tilted from an out-of-plane to an in-plane direction in the thin film by controlling the Li vacancy concentration within the hexagonal lattice framework. Partial inclusion of monoclinic-like phase is attributed to the breaking of macroscopic inversion symmetry along different directions and the emergence of ferroelectric polarization along the in-plane direction.
关键词： second harmonic generation,vacancy engineering,spatial inversion symmetry breaking,ferroelectric polarization rotation,LiNbO3 thin films
更新于2025-09-23 15:21:21
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Maturation of the Meniscal Collagen Structure Revealed by Polarization-Resolved and Directional Second Harmonic Generation Microscopy
摘要： We report polarization-resolved Second Harmonic Generation (p-SHG) and directional SHG (forward and backward, F/B) measurements of equine foetal and adult collagen in meniscus, over large field-of-views using sample-scanning. Large differences of collagen structure and fibril orientation with maturation are revealed, validating the potential for this novel methodology to track such changes in meniscal structure. The foetal menisci had a non-organized and more random collagen fibrillar structure when compared with adult using P-SHG. For the latter, clusters of homogeneous fibril orientation (inter-fibrillar areas) were revealed, separated by thick fibers. F/B SHG showed numerous different features in adults notably, in thick fibers compared to interfibrillar areas, unlike foetal menisci that showed similar patterns for both directions. This work confirms previous studies and improves the understanding of meniscal collagen structure and its maturation, and makes f/B and p-SHG good candidates for future studies aiming at revealing structural modifications to meniscus due to pathologies.
关键词： Second Harmonic Generation,meniscus,directional SHG,polarization-resolved,collagen
更新于2025-09-23 15:21:01
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Sierpi??ski Fractals as Plasmonic Metastructures for Second-Harmonic Generation
摘要： Metallic Sierpiński fractal metastructures made of gold nanoprisms that exhibit compatibility for both surface-enhanced Raman spectroscopy and second-harmonic generation have been prepared by electron-beam lithography. A sequential series of Sierpiński patterns were investigated up to the eighth-order generation. The presence of localized surface plasmon modes in the visible spectral range is due to the arrangement of the individual triangles forming the Sierpiński geometry, and was first exploited for surface-enhanced Raman measurements after functionalization of the plasmonic platform with p-Nitrothiophenol. Due to the non-centrosymmetric arrangement of the individual nanoprisms within the Sierpiński pattern, second-harmonic generation (SHG) microscopy measurements were conducted to evaluate the second-order nonlinear optical activity and its relationship to the spatial distributions of electromagnetic enhancement over the surface of the metastructure. Functionalization of the surface with molecules with an electron withdrawing group appears to further enhance the surface SHG signal.
关键词： Metamaterials,Plasmonics,Fractal plasmonics,Surface-enhanced Raman,Second-harmonic generation
更新于2025-09-23 15:21:01
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[Institution of Engineering and Technology 20th Italian National Conference on Photonic Technologies (Fotonica 2018) - Lecce, Italy (23-25 May 2018)] 20th Italian National Conference on Photonic Technologies (Fotonica 2018) - Second Harmonic Generation Circul Dichroism in Au Coated Gaas-based Nanowires
摘要： Nanostructures with broken symmetry can interact with circularly polarized light to mimic chiroptical (chiral-optical) effects, usually observable in chiral media. This phenomenon is known as extrinsic chirality. Second harmonic generation (SHG) is extremely sensitive to symmetry breaking, down to a single atomic monolayer and it has been extensively used as a probe of extrinsic chirality. Here we present SHG measurements of GaAs nanowires partially covered with Au, fabricated by a self-catalysed technique. The Au coated GaAs nanowires give rise to a dramatic circular dichroism in the generated second harmonic signal, compared to nanowires without coating.
关键词： plasmonic coating,extrinsic chirality,second harmonic generation,GaAs nanowires
更新于2025-09-23 15:21:01
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Recent advances with electro-optic polymers
摘要： In recent years the electro-optic polymers emerged as an important branch of material science. This growth and interest is fundamentally motivated by practical application of these materials in second-order nonlinear optics and in waveguiding configuration. Indeed, these materials marry excellent optical quality of amorphous r bonded polymers with enhanced first hyperpolarizability of imbedded organic nonlinear optical molecules. Although a big progress was achieved with them, concerning particularly the science, understanding and applications, some problems remain still incompletely solved, particularly the stability of induced polar order by the application of external electric field and the molecule aggregation. In this review paper we recall techniques of thin film fabrication, poling, characterization of NLO properties and discuss more precisely problems of molecule aggregation as well as the temporal decay of polar order. A novel 3D second-order NLO chromophores, namely the [2] paracyclophanes, which may help to limit the aggregation, are proposed. We show, in particular, that this molecule can be poled in doped PMMA thin films. Practical applications of electro-optic polymers are also reviewed and discussed.
关键词： pockels effect,electro-optic polymers,electric field poling,first hyperpolarizability,second harmonic generation,[2] paracyclophane,functionalized polymers
更新于2025-09-23 15:21:01
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Diode pumped Nd:YVO <sub/>4</sub> /LBO/Ba(NO <sub/>3</sub> ) <sub/>2</sub> Raman laser at 563 nm
摘要： Radiation at a wavelength of 563 nm was achieved using an all-solid-state laser system based on a diode-pumped actively Q-switched Nd3+:YVO4 laser with intra-cavity second harmonic generation in LBO followed by intra-cavity Raman conversion in Ba(NO3)2. The output power of 101 mW was achieved under a pump power of 5 W and a modulation frequency of 12.7 kHz with a slope conversion efficiency of 19%. The achieved peak power at 563 nm was 0.67 kW, which allows one to use this laser in medical treatment through selective excitation of deoxyhemoglobin into its long-wavelength absorption peak.
关键词： stimulated Raman scattering,intracavity second harmonic generation,563 nm,Raman laser
更新于2025-09-23 15:21:01
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Nonlinear Optics || The Nonlinear Optical Susceptibility
摘要： Nonlinear optics is the study of phenomena that occur as a consequence of the modification of the optical properties of a material system by the presence of light. Typically, only laser light is sufficiently intense to modify the optical properties of a material system in this manner. The beginning of the field of nonlinear optics is often taken to be the discovery of second-harmonic generation by Franken et al. (1961), shortly after the demonstration of the first working laser by Maiman in 1960. Nonlinear optical phenomena are "nonlinear" in the sense that they occur when the response of a material system to an applied optical field depends in a nonlinear manner on the strength of the applied optical field. For example, second-harmonic generation occurs as a result of the part of the atomic response that scales quadratically with the strength of the applied optical field. Consequently, the intensity of the light generated at the second-harmonic frequency tends to increase as the square of the intensity of the applied laser light.
关键词： Material system,Optical properties,Nonlinear optics,Laser light,Second-harmonic generation
更新于2025-09-23 15:21:01
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Second harmonic generation at 544a??nm of a femtosecond laser
摘要： We study second harmonic generation (SHG) at 544 nm of the 0-type (e + e - e) quasi-phase-matching based on a femtosecond laser at 1088 nm. The green pulse with the spectrum width of 0.6 nm and the peak power of 17.7 kW is obtained at the pump power density of 2.81 GW/cm2 and the conversion e?ciency is 21 %. As the propagation distance along the PPMgLN crystal increases, the spectrum at 544 nm becomes narrower and narrower and the pulse duration broadens very seriously.
关键词： Group velocity match,544 nm laser,Second harmonic generation,PPMgLN,Ultrafast optics,Femtosecond pulses
更新于2025-09-23 15:21:01
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Analyzing role of relaxation time on second harmonic generation and optical dielectric function of impurity doped quantum dots under the aegis of noise
摘要： Present study monitors the influence of relaxation time (τ) on second harmonic generation (SHG) and total optical dielectric function (TODF) of impurity containing quantum dot (QD) under the stewardship of Gaussian white noise. Two distinct roadways viz. ‘additive’ and ‘multiplicative’ have been exploited for the entrance of noise to the system. Both in absence and presence of noise the SHG and TODF peak positions do not exhibit any shift with increase in τ. The SHG peak values display monotonic behavior with the variation of τ. However, the TODF peak values delicately depend on variation of τ being guided by the presence of noise and also on its mode of introduction. Presence of additive (multiplicative) noise causes enhancement (suppression) of SHG and TODF peak values as τ varies over a range. The findings appear to be crucial in the fabrication of QD-based opto-electronic devices where role of noise deserves to be properly addressed.
关键词： Quantum dot,Gaussian white noise,Impurity,Total optical dielectric function,Relaxation time,Second harmonic generation
更新于2025-09-23 15:21:01