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ZnS Nanospheres for Optical Modulator in an Erbiuma??Doped Fiber Laser
摘要： Zinc sulfide (ZnS), which belongs to transition metal monochalcogenides, is a semiconductor material with wide direct band gap. It can potentially show some special applications (such as luminescence, phosphor, sensors, infrared window materials, photocatalysis) by changing the morphology, size, and crystal structure of semiconductor materials. However, ZnS nanospheres have not been studied as optical modulators until now. Herein, ZnS nanospheres are synthesized by the hydrothermal method and are used to realize optical modulators in an Er-doped fiber laser. The evanescent field effect is utilized to incorporate the ZnS nanospheres on a tapered fiber. Furthermore, with the increase in pump power, the modulation interval gradually decreases to a minimum of 34.36 ns corresponding to the modulation frequency of 29.1 MHz, which is the highest modulation frequency to our knowledge in a ring cavity all-fiber laser. These results demonstrate ZnS nanospheres together with the interaction of dispersion and nonlinearity in optical fibers can modulate the proposed lasers. This not only provides a new method for controlling the power and frequency of all optical modulators, but also marks an important step for ZnS materials in optics research and device applications.
关键词： optical modulators,nonlinear optical materials,ring cavity fiber lasers
更新于2025-09-19 17:13:59
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Rb <sub/>10</sub> Zn <sub/>4</sub> Sn <sub/>4</sub> S <sub/>17</sub> : A Chalcogenide with Large Laser Damage Threshold Improved from the Mn-Based Analogue
摘要： In the military and civilian fields, with the development of new technologies, high-powered nonlinear optical (NLO) crystals demonstrate broad application prospects. For purposes of designing a better NLO material, a new chalcogenide Rb10Zn4Sn4S17 was successfully designed with a high temperature solid-state method on the basis of previously reported compound Sr3MnSn2S8. The experimental results indicate that Rb10Zn4Sn4S17 possesses a prominent band gap of 3.59 eV, compared with the laser damage threshold (LDT) of Sr3MnSn2S8 (3 times that of AgGaS2); Rb10Zn4Sn4S17 shows an outstanding LDT about 5 times that of AgGaS2. Meanwhile, it has an ideal second harmonic generation (SHG) response approximately 0.7 times that of AgGaS2.
关键词： second harmonic generation (SHG),laser damage threshold (LDT),chalcogenide,nonlinear optical (NLO) crystals
更新于2025-09-19 17:13:59
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Ultrafast Charge Carrier Dynamics and Nonlinear Optical Absorption of InP/ZnS Core-Shell Colloidal Quantum Dots
摘要： Understanding of ultrafast carrier dynamics in InP/ZnS colloidal quantum dots (QDs) is essential for their optoelectronic applications. In this paper, we have successfully fabricated high-quality InP/ZnS core-shell QDs with quantum yield (QY) of 47%. Time resolved photoluminescence (TRPL), femtosecond transient absorption (TAS) measurements were performed to characterize the carrier injection, relax and transition process in the InP/ZnS QDs. It is found that the photoexcited carrier first injected to ZnS shell in 2 ps, then relaxed to alloyed layer between ZnS shell and InP core in 7.4 ps, next relaxed to different energy levels in InP core in about 170 ps, finally recombined by charged and neutral excitons transition in 4.1 ns and 26.7 ns, respectively. Additionally, the two-photon absorption (TPA) coefficient obtained from Z-scan measurement indicates that InP/ZnS QDs possess good nonlinearly optical properties. Our research is significant for the improvement and engineering of InP/ZnS QDs based materials for optoelectronic applications.
关键词： quantum dots,InP/ZnS,ultrafast carrier dynamics,nonlinear optical absorption,optoelectronic applications
更新于2025-09-19 17:13:59
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Xa??Shaped Alignment of Chromophores: Potential Alternative for Efficient Organic Terahertz Generators
摘要： Efficient broadband organic terahertz (THz) generators using X-shaped alignment of the nonlinear optical chromophores, as an alternative to the parallel alignment of chromophores in benchmark organic crystals, are reported. All the developed six organic benzothiazolium crystals exhibit an isomorphic X-shaped alignment of chromophores, resulting in an unprecedentedly large off-diagonal optical nonlinearity (>100 × 10?30 esu), which presents one of the largest off-diagonal optical nonlinearity of organic crystals. The benzothiazolium crystals exhibit efficient broadband THz wave generation employing the off-diagonal optical nonlinearity, in contrast to the present state-of-the-art organic THz generators that mostly utilize diagonal optical nonlinearity. For using off-diagonal and diagonal optical nonlinearities, the polarization of the optical pump is perpendicular and parallel, respectively, to the polar axis of crystals. In addition to a large THz wave generation efficiency with one order of magnitude higher peak-to-peak THz electric field than that generated in a 1.0-mm-thick inorganic benchmark ZnTe crystal, the benzothiazolium crystals generate broadband THz spectra with an upper cut-off frequency of near 8 THz, and the absence of strong absorption dimples in the range of 0.5?4 THz. Therefore, the X-shaped alignment of chromophores presents an interesting potential alternative for efficient broadband organic THz generators.
关键词： nonlinear optical crystals,THz generators,organic crystals
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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Nonlinear optical properties of lens-shaped core/shell quantum dots coupled with a wetting layer: effects of transverse electric field, pressure, and temperature
摘要： In this study, we numerically determined the intra-band transition lifetime of carriers as well as, the linear, nonlinear, and total absorption coefficients fro lens-shaped core/shell quantum dot structures. Our computations considered the combined effects of the wetting layer, pressure, applied transverse electric field, temperature, and core/shell sizes. By using suitable choices for these parameters, we found that a red or blue shift in the energy of the absorption spectrum could be achieved. In addition, the largest absorption coefficient was obtained when an intense transverse electric field was applied along the diagonal of the cross section of the structure considered. Hence, the magnitude of the absorption coefficient increased by 50%. Moreover, our results showed that the transition lifetime of the carriers decreasedas the temperatureincreased, whereas it increased as the pressure increased. Comparative analysis of a semi-spherical core/shell quantum dot system showed that the transition lifetime was shorter than that of the lens-shaped core/shell quantum dot structure, which was 255 ns.
关键词： Nonlinear optical properties,Electric field,Pressure,Temperature,Lens-shaped core/shell quantum dot
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) - Spectroscopic and Structural Properties of Yb <sup>3+</sup> -Doped and Undoped 2D-Mos <sub/>2</sub> Thin Films for Optoelectronic and Photonic Device Applications
摘要： Molybdenum disulphide (MoS2) has layered structure and is classed as a transition metal-disulphide (TMD) material. Recently it has drawn significant attention for exploring optoelectronic and photonic properties on sub-nanometre scale, with a potential for accessing quantum interactions [1]. The electronic structure and stoichiometry of TMDs make them distinguishable from the metallic graphene, as the TMDs depict a clear bandgap, as in compound semiconductors [2], which is quite attractive for device engineering and applications in photovoltaic, energy storage, and bandgap engineered light-sources [3]. In this research, the fabrication of undoped and Yb3+-ion doped MoS2 nanometre (nm)-scale thin films are discussed using femto-second pulsed laser deposition (fs-PLD) and the structural and spectroscopic properties of fs-PLD are compared with liquid-phase epitaxy grown undoped MoS2 films. Such a comparative analysis may offer materials fabrication platform in future for engineering optoelectronic and photonic devices on silica glass and silicon platforms.
关键词： DFT,Raman spectroscopy,nonlinear optical properties,Molybdenum disulphide,fs-PLD,photonic devices,Yb3+-doped,optoelectronic,thin films
更新于2025-09-19 17:13:59
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Niobium disulfide as a new saturable absorber for an ultrafast fiber laser
摘要： Group VB transition metal dichalcogenides (TMDCs) are emerging two-dimensional materials and have attracted significant interests in the fields of physics, chemistry, and material sciences. However, there are very few reports about the optical characteristics and ultrafast photonic applications based on group VB TMDCs so far. In this work, we have calculated the niobium disulfide (NbS2) band structure by the density functional theory (DFT), which has revealed that NbS2 is a metallic TMDC. In addition, we have prepared an NbS2-microfiber device and the nonlinear optical characteristics have been investigated. The modulation depth, saturation intensity and non-saturable loss have been measured to be 13.7%, 59.93 MW cm?2 and 17.74%, respectively. Based on the nonlinear optical modulation effect, the Er-doped fiber (EDF) laser works in the soliton mode-locking state with the pump power of 94–413 mW. The pulse duration of 709 fs and the maximum average output power of 23.34 mW have been obtained at the pump power of 413 mW. The slope efficiency is as high as 6.79%. Compared to the recently reported studies based on TMDCs comprehensively, our experimental results are better. These experimental results demonstrate that NbS2 with excellent nonlinear optical properties can be used as a promising candidate to advance the development of ultrafast photonics.
关键词： Niobium disulfide,ultrafast fiber laser,saturable absorber,mode-locking,nonlinear optical properties
更新于2025-09-19 17:13:59
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Methyl Made Noncentrosymmetric Stacking: A Promising Organic Single Crystal for Highly Efficient Terahertz-wave Generation
摘要： Regulating secondary bonds in organic compounds is one of the important routes to design practical materials with excellent performances. However, it is still a great challenge to control molecular arrangement and spatial configuration by changing limited substituent groups. Herein, two indolium-based (C19H20NO)+ crystals, centric OHI-CBS and acentric OHI-T were synthesized and grown by evaporation method. An intriguing structural change from centrosymmetric (P21/c) to noncentrosymmetric (Cc) space group was obtained by a simple substitution from chloro- to methyl. Theoretical calculations demonstrate hydrogen bonds and π-π interactions make a dominated contribution to molecular spatial alignment. Meanwhile, OHI-T crystal exhibits prominent nonlinearity about 0.7 times that of the benchmark OH1 crystal, wide band gap (2.47 eV), wide transparency range (504 - 2100 nm), and remarkably efficient output energy among 0.1 - 20 THz region, suggesting it is a potential nonlinear optical media for THz-wave generation. This work realizes the rational crystal structural regulation by simple molecular subsitution and provides a feasible design strategy for other organic optoelectronic functional materials.
关键词： indolium-based crystals,π-π interactions,hydrogen bonds,THz-wave generation,nonlinear optical media
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