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GaSe saturable absorber for mode-locked Er-doped fiber laser
摘要： A GaSe-PVA based saturable absorber (SA) is prepared by liquid-phase stripping method. The linear and nonlinear transmission spectrum, AFM, SEM and Raman spectrum are used to characterize the SA, the modulation depth of 6.4% and the saturation intensity of 72 MW/cm2 indicated that the GaSe nanosheets can be employed as SA for mode-locked (ML) operation in Er-doped fiber laser (EDFL). The passively mode-locked operation with the output power of 29.1 mW, pulse width of 4.3 ps and repetition rate of 8.849 MHz can be obtained by GaSe-PVA based SA.
关键词： mode-locked,Er-doped fiber laser,GaSe saturable absorber
更新于2025-11-28 14:24:03
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Probing interlayer excitons in a vertical van der Waals p-n junction using scanning probe microscopy technique
摘要： Two dimensional (2D) semiconductors feature exceptional optoelectronic properties controlled by strong confinement in one dimension. In this contribution, we studied interlayer excitons in a vertical p-n junction made of bilayer n-type MoS2 and few layers of p-type GaSe using current sensing atomic force microscopy (CSAFM). The p-n interface is prepared by mechanical exfoliation onto highly ordered pyrolytic graphite (HOPG). Thus the heterostructure creates an ideal layered system with HOPG serving as the bottom contact for the electrical characterization. Home-built Au tips are used as the top contact in CSAFM mode. During the basic diode characterization, the p-n interface shows strong rectification behavior with a rectification ratio of 104 at ±1 V. The I-V characteristics reveal pronounced photovoltaic effects with a fill factor of 0.55 by an excitation below the band gap. This phenomenon can be explained by the dissociation of interlayer excitons at the interface. The possibility of the interlayer exciton formation is indicated by density functional theory (DFT) calculations on this heterostructure: the valence band of GaSe and the conduction band of MoS2 contribute to an interface-specific state at an energy of about 1.5 eV. The proof of excitonic transitions to that state is provided by photoluminescence measurements at the p-n interface. Finally, photocurrent mapping at the interface under an excitation wavelength of 785 nm provides evidence of efficient extraction of such excitons. Our results demonstrate a pathway towards a two dimensional device for future optoelectronics and light harvesting assisted by interlayer excitons in a van der Waals heterostructure.
关键词： optoelectronics,van der Waals heterojunction,GaSe,density functional theory,MoS2,interlayer exciton,p-n junction
更新于2025-09-23 15:23:52
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GaSe saturable absorber for mode-locked Yb-doped fiber laser at 1.04???μm
摘要： Transition-metal dichalcogenides, such as tungsten disulfide (WS2) and molybdenium disulfide (MoS2), are highly anisotropic layered materials and have attracted growing interest from basic research to practical applications due to their exotic physical property that may complement graphene and other semiconductor materials. GaSe nanosheets are found to exhibit broadband nonlinear saturable absorption property, and saturable absorbers are fabricated by depositing GaSe nanosheets on side-polished fibers. Attributing to the weak evanescent field and long interaction length, the GaSe nanosheets are not exposed to large optical intensity, which allows the saturable absorber to work at the high-power regime. The saturable absorbers are used to mode locked dispersion-managed soliton fiber lasers.
关键词： Dispersion-managed soliton,Fiber lasers,Mode-locked,GaSe
更新于2025-09-23 15:21:01
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Patterning GaSe by High-Powered Laser Beams
摘要： We report the high-powered laser modification of the chemical, physical, and structural properties of the two-dimensional (2D) van der Waals material GaSe. Our results show that contrary to expectations and previous reports, GaSe at the periphery of a high-power laser beam does not entirely decompose into Se and Ga2O3. In contrast, we find unexpectedly that the Raman signal from GaSe gets amplified around regions where it was not expected to exist. Atomic force microscopy (AFM), dielectric force microscopy (DFM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) results show that laser irradiation induces the formation of nanoparticles. Our analyses demonstrate that, except for a fraction of Ga2Se3, these nanoparticles still belong to the GaSe phase but possess different electrical and optical properties. These changes are evidenced in the increased Raman intensity attributed to the near-resonance conditions with the Raman excitation laser. The elemental analysis of nanoparticles shows that the relative selenium content increased to as much as 70% from a 50:50 value in stoichiometric GaSe. This elemental change is related to the formation of the Ga2Se3 phase identified by Raman spectroscopy at some locations near the edge. Further, we exploit the localized high-power laser processing of GaSe to induce the formation of Ag?GaSe nanostructures by exposure to a solution of AgNO3. The selective reaction of AgNO3 with laser-irradiated GaSe gives rise to composite nanostructures that display photocatalytic activity originally absent in the pristine 2D material. The photocatalytic activity was investigated by the transformation of 4-nitrobenzenethiol to its amino and dimer forms detected in situ by Raman spectroscopy. This work improves the understanding of light?matter interaction in layered systems, offering an approach to the formation of laser-induced composites with added functionality.
关键词： GaSe,photocatalytic activity,nanoparticles,high-powered laser,Raman spectroscopy
更新于2025-09-23 15:21:01
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Nonlinear Optical Absorption in GaSe upon Laser Excitation
摘要： The nonlinear absorption in GaSe crystals at high optical excitation levels is experimentally studied. A Nd:YAG laser (first and second harmonics, 1064 and 532 nm) and a liquid laser (tuning range 594–643 nm) were used as excitation sources. It is shown that the features observed in the exciton resonance region of the absorption, luminescence, and photoconductivity spectra of GaSe crystals at high optical excitation levels can be explained by exciton–exciton interaction and Coulomb interaction screening by free carriers.
关键词： GaSe,photoconductivity,nonlinear absorption,luminescence
更新于2025-09-23 15:21:01
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Controlled synthesis of GaSe microbelts for high-gain photodetectors induced by the electron trapping effect
摘要： GaSe microbelts were successfully synthesized using Ga/Ga2Se3 as the precursor mixture, where excess Ga was required to serve as the metal catalyst. Meanwhile, a spontaneously oxidized surface amorphous oxide (GaOx) layer formed, which induced a built-in electric field perpendicular to the surface. Benefiting from this effect, a GaSe microbelt-based photodetector attained a high responsivity of B3866 A W(cid:2)1 and a photoconductive gain of up to B1.06 (cid:3) 104. This study sheds light on the controlled synthesis of microstructures and provides a device design concept for high-performance micro/nano optoelectronics.
关键词： high-gain,electron trapping effect,photodetector,GaSe microbelts
更新于2025-09-19 17:13:59
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GaSe/MoS <sub/>2</sub> Heterostructure with Ohmica??Contact Electrodes for Fast, Broadband Photoresponse, and Selfa??Driven Photodetectors
摘要： In this letter, the vertically-stacked GaSe/MoS2 heterostructures with indium tin oxide (ITO) and Ni/Au as contact electrodes are successfully fabricated, respectively. The GaSe/MoS2 heterostructure exhibits a broadband photoresponse covering the range of visible to near-infrared spectra at room temperature without external bias voltage. When ITO serves as contact electrodes, a high rectification ratio, i.e., 1.5 × 104 at VDS = ±1 V, and an excellent photoelectric performance, i.e., responsivity of ≈0.67 A W-1, specific detectivity of ≈2.3 × 1011 cm Hz1/2 W-1 and external quantum efficiency of ≈160% at the wavelength of 520 nm is achieved. Moreover, the GaSe/MoS2 heterostructure with Ohmic-contact ITO electrodes demonstrates a faster response time of 155 μs, which is 4 times faster than the GaSe/MoS2 heterostructure with Ni/Au electrodes and about 300 times faster than previous reports. These results reveal the presence of an abrupt p–n junction between GaSe and MoS2 and significant role of electrode-contact mode in determining the photoelectric properties of GaSe/MoS2 heterostructure.
关键词： photoresponse,GaSe/MoS2 heterostructure,self-driven photodetector,Ohmic-contact
更新于2025-09-16 10:30:52
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Three-Terminal Memtransistors Based on Two-Dimensional Layered Gallium Selenide Nanosheets for Potential Low-Power Electronics Applications
摘要： A multi-terminal hybrid system named memtransistor has recently been proposed by combining the concepts of both memristor and field effect transistor (FET) with two-dimensional (2D) layered materials as the active semiconductor layer. In the memtransistors, the gate voltages are capable of modulating not only the transport properties of the fabricated FET, but also the resistive switching (RS) behaviors of the memristor. Herein, we employ mechanically exfoliated 2D layered GaSe nanosheets to prepare GaSe based three-terminal memtransistors. By using Ag as the electrodes, the memristor exhibits non-volatile bipolar RS characteristics. More importantly, under exposure to air for one week, the RS behaviors are dramatically enhanced with the ON/OFF ratio reaching up to 5.3 × 105 and ultralow threshold electric field of ~3.3 × 102 Vcm-1. The ultralow threshold electric field of GaSe based memristor could be related to the low migration energy of the intrinsic Ga vacancy in p-type GaSe. Moreover, the GaSe-based memristor shows long-term retention (~104 s) and high cycling endurance (~5000 cycles) simultaneously. Hence, the fabricated three-terminal 2D GaSe memtransistors possess high performance with large switching ratios, ultralow threshold electric field, good endurance and long-term retention. Furthermore, the device demonstrates gate tunability in RS characteristics, suggesting the promising applications in multi-terminal electronic devices with low power consumption and complex functionalities, ranging from non-volatile memory, logic device to neuromorphic computing.
关键词： memtransistors,memristors,2D materials,GaSe,resistive switching
更新于2025-09-04 15:30:14