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Tunable passively Q-switched ytterbium-doped fiber laser using MoWS2/rGO nanocomposite saturable absorber
摘要： We demonstrated a tunable Q-switched ytterbium-doped fiber laser (YDFL) using MoWS2/rGO nanocomposite as passive saturable absorber. Further, the Mo1?xWxS2/rGO nanosheets, with x proportion of 0.2, are synthesized using hydrothermal exfoliation technique. The proposed nanocomposite-PVA based thin film is fabricated by mixing the MoWS2/rGO nanosheets with polyvinyl alcohol (PVA). The fabricated thin film is sandwiched between two fiber ferrules to realize the proposed saturable absorber (SA). Further, the proposed MoWS2/rGO-PVA based thin film SA exhibits a fast relaxation time and a high damage threshold which are suitable to realize a Q-switched pulsed laser with a tunable wavelength range of 10 nm that extends from 1028 nm to 1038 nm. For the highest pump power of 267.4 mW, the generated Q-switched pulses exhibit a narrow pulse width of 1.22 μs, the pulse repetition rate of 90.4 kHz, the highest pulse energy of 2.13 nJ and its corresponding average power of 0.193 mW. To the best of author’s knowledge, this is the first realization of a tunable Q-switching fiber laser in a 1 μm wavelength using MoWS2/rGO nanocomposite saturable absorber.
关键词： Saturable absorber,Molybdenum,Tungsten disulfide,Q-switched fiber laser,Transition metal dichalcogenides
更新于2025-11-28 14:24:03
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Investigation of Surface Plasmon Resonance (SPR) in MoS2- and WS2-Protected Titanium Side-Polished Optical Fiber as a Humidity Sensor
摘要： In this paper, we report the effects of a side-polished fiber (SPF) coated with titanium (Ti) films in different thicknesses, namely 5 nm, 13 nm, and 36 nm, protected by a thin layer of transition metal dichalcogenides (TMDCs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2), which provide ultra-sensitive sensor-based surface plasmon resonance (SPR) covering from the visible to mid-infrared region. The SPF deposited with Ti exhibits strong evanescent field interaction with the MoS2 and WS2, and good optical absorption, hence resulting in high-sensitivity performance. Incremental increases in the thickness of the Ti layer contribute to the enhancement of the intensity of transmission with redshift and broad spectra. The findings show that the optimum thickness of Ti with 36 nm combined with MoS2 causes weak redshifts of the longitudinal localized surface plasmon resonance (LSPR) mode, while the same thickness of Ti with WS2 causes large blueshifts. The redshifts are possibly due to a reduced plasmon-coupling effect with the excitonic region of MoS2. The observed blueshifts of the LSPR peak position are possibly due to surface modification between WS2 and Ti. Changing the relative humidity from 58% to 88% only elicited a response in Ti/MoS2. Thus, MoS2 shows more sensitivity on 36-nm thickness of Ti compared with WS2. Therefore, the proposed fiber-optic sensor with integration of 2D materials is capable of measuring humidity in any environment.
关键词： tungsten disulfide (WS2),side-polished fiber (SPF),molybdenum disulfide (MoS2)
更新于2025-11-28 14:23:57
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Quantum Calligraphy: Writing Single-Photon Emitters in a Two-Dimensional Materials Platform
摘要： We present a paradigm for encoding strain into two dimensional materials (2DM) to create and deterministically place single photon emitters (SPEs) in arbitrary locations with nanometer-scale precision. Our material platform consists of a 2DM placed on top of a deformable polymer film. Upon application of sufficient mechanical stress using an atomic force microscope tip, the 2DM/polymer composite deforms, resulting in formation of highly localized strain fields with excellent control and repeatability. We show that SPEs are created and localized at these nanoindents, and exhibit single photon emission up to 60K, the highest temperature reported in these materials. This quantum calligraphy allows deterministic placement and real time design of arbitrary patterns of SPEs for facile coupling with photonic waveguides, cavities and plasmonic structures. In addition to enabling versatile placement of SPEs, these results present a general methodology for imparting strain into 2DM with nanometer-scale precision, providing an invaluable tool for further investigations and future applications of strain engineering of 2DM and 2DM devices.
关键词： tungsten disulfide,atomic force microscopy,two-dimensional materials,single photon emitter,strain engineering
更新于2025-09-23 15:22:29
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Synthesis of Tungsten Disulfide and Molybdenum Disulfide Quantum Dots and their Applications
摘要： With fascinating optical, electronic, and mechanical properties, tungsten disulfide (WS2) and molybdenum disulfide (MoS2) quantum dots (QDs) are promising for related applications. Their bandgap energy, photoluminescence and electrochemical properties are closely related to their size, morphology, dimensionality, crystal phase and structure. In this review, we introduce the crystal phases and structures of WS2 and MoS2 QDs followed by a summary of their physical and chemical synthetic methods and their applications in light-emitting devices (LEDs), supercapacitors and others. Additionally, the advantages and limitations of different synthetic strategies and challenges in these promising fields are discussed on the basis of current development.
关键词： Synthesis methods,Applications,Quantum dots,Molybdenum disulfide,Tungsten disulfide
更新于2025-09-23 15:21:01
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Enhanced photoresponse and surface charge transfer mechanism of graphene-tungsten disulfide heterojunction
摘要： Two dimensional (2D) materials based heterostructures have gained profound interest in optoelectronics and electronic technology due to additional functionalities over the individual structures. This study demonstrates the fabrication and characterization of van der Waal heterostructure by selective coverage of graphene (Gr) with tungsten disulfide (WS2). The electrical transport measurements divulge the tweaking of charge carriers in graphene after WS2 coverage. Such architecture provides route towards the formation of heterojunction within graphene FET based on surface charge transfer between Gr/WS2 heterointerface. Furthermore, the exposure of device towards deep ultraviolet light (DUV) enhances the charge transfer mechanism and as a result more pronounced junction is observed. The photoelectrical characterization of heterostructure is also investigated by calculating detectivity (D*), external quantum efficiency (EQE) photoresponsivity (Rλ). Our results suggest that 2D heterostructures in combination with DUV irradiations are more efficient and suitable choice to selectively tune the properties of 2D material-based optoelectronic devices.
关键词： p-n junction,Tungsten disulfide,Graphene,Photoresponse,Deep ultraviolet light (DUV),Heterostructure
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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Tm <sup>3+</sup> -Doped Harmonic Dissipative Soliton Mode-Locked Fiber Laser at 1.93 $\mu$ m Based on Tungsten Disulfide in Anomalous Dispersion Regime
摘要： We report a harmonic dissipative soliton 1.93 μm thulium fiber laser based on a tungsten disulfide (WS2) saturable absorber (SA) in the anomalous dispersion regime. The multilayer WS2 nanosheets were prepared by liquid phase exfoliation method and the SA was fabricated by dropping WS2 solution onto a gold mirror. The transferred WS2 SA had a modulation depth of 2.5% and a saturation intensity of 0.82 MW/cm2. By incorporating the SA into a linear Tm3+ fiber laser cavity, harmonic mode-locked dissipative soliton laser was achieved at 1930 nm with the spectral width of 8 nm, the pulse energy of 3 nJ, the pulse width of 3.6 ns, and the repetition rate of 56.3 MHz. Based on the experimental results, it is shown that with the presence of harmonic mode-locking in 2 μm wavelength region, the multilayer WS2 serving as a SA was verified to be a good candidate for broadband high-energy mode-locking. The order of the harmonic dissipative soliton mode-locked pulses remains the same along with the increasing pump power.
关键词： 2 μm fiber laser,2D material,tungsten disulfide,Mode-locked fiber laser,Tm3+-doped fiber
更新于2025-09-12 10:27:22
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Nonlinear optical properties of tungsten disulfide as saturable absorber based on Q-switched fiber laser
摘要： In this paper, nonlinear optical properties of tungsten disulfide are studied. Tungsten disulfide (WS2) is prepared as saturable absorber (SA) with the microstructured optical fiber. When the SA based on WS2 is assembled into a fiber laser, Q-switched operation is demonstrated. The 2 nm spectral width is obtained at the central wavelength of 1531 nm. The signal-to-noise ratio is about 80 dB, which indicates that the fiber laser is very stable. The shortest pulse duration is 800 nm at the maximum input power of 650 mW. The conclusion shows that WS2 is a good nonlinear optical material.
关键词： Saturable absorber,Fiber laser,Tungsten disulfide,Nonlinear optical properties
更新于2025-09-11 14:15:04
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Ruthenium decorated tungsten disulfide quantum dots for CO2 gas sensor
摘要： In this work, a selective chemi-resistive gas sensor for carbon dioxide gas detection at room temperature (~ 25 °C) was successfully fabricated, where ruthenium decorated tungsten disulfide (Ru@WS2) quantum dots (QDs) have been used as the sensing material. A mixed solvent of lithium hydroxide (LiOH·H2O) and N-Methyl-2-pyrrolidone (NMP) were used to obtain the Ru decorated WS2 QD from the exfoliated WS2 nanoflakes. Then the prepared WS2 QD and Ru@WS2 QD were confirmed using different material characterisation techniques. The gas sensors were then exposed to various concentration of CO2 gas in dry air condition. Also, the effect of humidity of both the sensors in 5000 ppm CO2 gas has been studied. The Ru@WS2 QDs based sensor showed superior sensitivity and good selectivity to CO2 gas in comparison with isopropanol, acetone, ethanol, methanol and benzene at room temperature than WS2 QD. The sensor showed an increase in resistance when exposed to CO2 gas ranging from 500 to 5000 ppm, indicating p-type characteristics. Ru@WS2 QD shows less effect at different humid condition compares to WS2 QD as a CO2 gas sensor.
关键词： Ruthenium decorated tungsten disulfide (Ru@WS2),Transition metal dichalcogenides (TMDC),Quantum Dot (QD),Sensitivity,Selectivity,Gas sensor
更新于2025-09-11 14:15:04
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Wafer-scale single-crystal hexagonal boron nitride film via self-collimated grain formation
摘要： Although polycrystalline hexagonal boron nitride (PC-hBN) has been realized, defects and grain boundaries still cause charge scatterings and trap sites, impeding high-performance electronics. Here, we report a method of synthesizing wafer-scale single-crystalline hBN (SC-hBN) monolayer films by chemical vapor deposition. The limited solubility of boron (B) and nitrogen (N) atoms in liquid gold promotes high diffusion of adatoms on the surface of liquid at high temperature to provoke the circular hBN grains. These further evolve into closely packed unimodal grains by means of self-collimation of B and N edges inherited by electrostatic interaction between grains, eventually forming an SC-hBN film on a wafer scale. This SC-hBN film also allows for the synthesis of wafer-scale graphene/hBN heterostructure and single-crystalline tungsten disulfide.
关键词： single-crystalline,hexagonal boron nitride,wafer-scale,tungsten disulfide,chemical vapor deposition,graphene/hBN heterostructure
更新于2025-09-10 09:29:36