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Lasers with emission wavelengths of 1.5 mu m are suitable for the eye-safe band and transparency region of the atmosphere. During extremely bad weather conditions, the penetration is stronger than the traditional 1 mu m and visibl...
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Lasers with emission wavelengths of 1.5 mu m are suitable for the eye-safe band and transparency region of the atmosphere. During extremely bad weather conditions, the penetration is stronger than the traditional 1 mu m and visible band; thus, they are extensively employed in remote sensing, ranging, and imaging. In recent years, Er:Yb: glass has been widely used for generating 1.5 mu m lasing, particularly for the generation of passively Q-switched pulses. Herein, different types of saturable absorbers (SAs) for Er:Yb:glass Q-switching have been reviewed, and the development of passively Q-switched Er:Yb:glass lasers based on these SAs has been discussed.
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In recent years, vortex beams with orbital angular momentum (OAM) have attracted more and more attention. The wavefront of the OAM beams is helical, the intensity at the center of the beam is zero, and there is a phase singularity...
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In recent years, vortex beams with orbital angular momentum (OAM) have attracted more and more attention. The wavefront of the OAM beams is helical, the intensity at the center of the beam is zero, and there is a phase singularity. Because of the novel phase characteristics of OAM beams, they have a wide application prospect in the fields of optical communication, rotating body detection and particle manipulation. Therefore, the research on the generation technology of OAM beams and their application range are of instructive significance to the future experiments. In this paper, the common beams carrying OAM are introduced, and the techniques of generating OAM beams in free space are summarized, including intracavity conversion method and extracavity conversion method. The application range of OAM beams studied at present is discussed, and the development trend of OAM beams is prospected. The purpose of this paper is to provide reference and guidance for related experiments of OAM beams in the future.
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In recent years, 589 nm lasers have attracted much attention in the fields of laser sodium guide star, laser radar, and adaptive optics. Therefore, the sodium guide star technology at 589 nm has been particularly topical. The sodi...
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In recent years, 589 nm lasers have attracted much attention in the fields of laser sodium guide star, laser radar, and adaptive optics. Therefore, the sodium guide star technology at 589 nm has been particularly topical. The sodium guide star technology requires that the average power should be Watt-level for the continuous-wave yellow laser which having narrow-linewidth and are capable of being tuned to match transition lines accurately. According to the generation method, the sodium guided star laser can be divided into four types: dye lasers, solid-state lasers, optically pumped semiconductor lasers, and fiber lasers. Solid-state laser includes sum-frequency generation, stimulated Raman scattering and optical parametric amplifier. Among them, sum-frequency generation lasers are used mostly. The development history and state of the art of them are expatiated, which is useful reference for the future research in this field.
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In this paper, we investigated the influence of Semiconductor Saturable Absorber Mirror (SESAM) parameters on pulse evolution of passively mode-locked fiber laser at different repetition rates. Based on the Nonlinear Schrodinger E...
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In this paper, we investigated the influence of Semiconductor Saturable Absorber Mirror (SESAM) parameters on pulse evolution of passively mode-locked fiber laser at different repetition rates. Based on the Nonlinear Schrodinger Equation, the mode-locked process of the SESAM passively mode-locked fiber laser and the pulse evolution were simulated. Furthermore, the impact of modulation depth of a SESAM together with saturation intensity on mode-locking at different repetition rates have been analyzed. According to the simulation, at low repetition rate, when the laser operates at mode-locked state, the modulation depth of SESAM is larger, while the modulation depth is smaller when pulse modulation phenomenon caused by excessive modulation depth occurs in the cavity. At high repetition rate, the range of saturation intensity is much larger when the laser operates at mode-locked state. The presented numerical study provides valuable guidance for the design and development of mode-locked fiber lasers operating at different repetition rates.
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A novel trench-assisted dual-mode multi-core fiber with large-mode-field-area is proposed. The structure consists of 17 conventional cores and two air holes according to a regular hexagon, which can realize strict dual-mode transm...
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A novel trench-assisted dual-mode multi-core fiber with large-mode-field-area is proposed. The structure consists of 17 conventional cores and two air holes according to a regular hexagon, which can realize strict dual-mode transmission. The structural parameters' effect on mode transmission characteristics, mode-field-area, and bending loss are analyzed systematically. By optimizing the structural parameters, the mode-field-area of the fundamental mode can reach 2100.619 mu m(2). The introduction of the trench with a lower refractive index than cladding can reduce the bending loss to 9.88 x 10(-4) dB/m when the bending radius is 2.3 cm. Besides, the structural design is flexible, and the manufacturing process is simple, which has broad application prospects. (C) 2021 Optical Society of America
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The exploration of electrocatalysts with high performance of hydrogen evolution reaction (HER) in all media is essential for developing clean energies. Single-atom catalysts (SACs) have attracted wide attentions owing to their max...
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The exploration of electrocatalysts with high performance of hydrogen evolution reaction (HER) in all media is essential for developing clean energies. Single-atom catalysts (SACs) have attracted wide attentions owing to their maximum atom utilization and excellent catalytic activity. In this work, the HER activities of transition metal (TM) (TM = Fe, Co, Ni and Cu) SACs on two-dimensional SnO monolayer are studied using density functional theory. We found that the low-cost TM SACs can exhibit high HER activity in wide pH-range. Especially, Co SACs show promising catalytic activity with the Gibbs free energy of hydrogen adsorption (Delta G(H*)) as low as similar to 0.015 eV, which are also high active in either acidic or alkaline environments. With the experimentally inevitable oxygen vacancies in SnO, the Delta G(H*) of Co, Ni and Cu SACs are almost zero, which are competitive with the precious catalyst Pt(111) (-0.09 eV). The exceptional HER activity is correlated to the enhanced electron states close to the Fermi level as well as the d-band center positions of the TM. Our work opens new avenues for engineering low-cost TM SACs with pH-universal HER performance, which is of great importance in practical applications.
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In this paper, a trench-assisted large-mode-field-area multi-core fiber with an air-hole structure composed of 21 conventional fiber cores and 16 air holes is proposed, and it can realize dual-mode transmission. By adjusting the s...
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In this paper, a trench-assisted large-mode-field-area multi-core fiber with an air-hole structure composed of 21 conventional fiber cores and 16 air holes is proposed, and it can realize dual-mode transmission. By adjusting the structural parameters, the effective mode field area of fundamental mode can be up to 1916.042 mu m(2) at 1550 nm. In addition, the fiber has good bending characteristics by adding a trench with a lower refractive index than the cladding. When the bending radius is 1.4 cm, the bending loss is low to 2.96 x 10(-3) dB/m. This fiber is of great significance for the design of bending insensitive fiber.
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This study demonstrated the use of a highly compact nanosecond laser system operating at 532 nm and producing a maximum output power of 70 W with a pulse width of 5 ns at 0.5 kHz, for space debris tracking. To improve the ranging ...
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This study demonstrated the use of a highly compact nanosecond laser system operating at 532 nm and producing a maximum output power of 70 W with a pulse width of 5 ns at 0.5 kHz, for space debris tracking. To improve the ranging accuracy while minimizing the influence of the pulse noise, a bidirectional Q-switch was adopted in the oscillator to generate a short pulse width with less tailing. The laser was applied for low-Earth orbit space debris tracking, and space debris with the farthest distance of 1701.9 km at the minimum radar cross-section of 1 m(2) could be detected with a ranging precision of up to 26.90 cm.
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Two-dimensional ferromagnetic semiconductors hold great promise for next-generation spintronic applications. However, candidates with high Curie temperature (T-c) are still lacking. Using the first-principles calculations, the PtB...
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Two-dimensional ferromagnetic semiconductors hold great promise for next-generation spintronic applications. However, candidates with high Curie temperature (T-c) are still lacking. Using the first-principles calculations, the PtBr3 monolayer is found to exhibit ferromagnetic order above the room temperature. The formation of PtBr3/WSe2 van der Waals heterostructures can increase the T-c to similar to 410 K by additional super-exchange path of Pt-Se-Pt. The spin-exchange interactions for this path is as strong as similar to 22 meV, which is superior to most other magnetic system. The out-of-plane compression further boosts the T-c to similar to 636 K. The interlayer magnetic coupling is highly tunable depending on the stacking alignment, which closes or weakens some super-exchange channels. In addition, the interlayer interaction leads to a phase transition from half-metal to semiconductor, which greatly promotes its potential in spintronic applications. The strong stacking dependent feature is feasible to manipulate the magnetic orders by external strain or mechanical motion.
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Physical vapor deposition has emerged as a promising strategy for efficient and stable all-inorganic perovskite light-emitting devices (PeLEDs). However, the thermally evaporated PeLEDs still suffer from unsatisfactory optoelectri...
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Physical vapor deposition has emerged as a promising strategy for efficient and stable all-inorganic perovskite light-emitting devices (PeLEDs). However, the thermally evaporated PeLEDs still suffer from unsatisfactory optoelectrical performance because of the massive nonradiative defects. Herein, we demonstrate an efficient bilateral interfacial defectpassivation strategy toward high-performance PeLEDs with a thermally deposited CsPbBr3 emissive layer (EML). Specifically, the nonradiative defects from the bulk as well as the EML/charge transport layer (CTL) interface are significantly suppressed by implementing the 3-amino-1-propanol (3AP)-modified PEDOT:PSS and introducing ammonium salts, respectively. Simultaneously, both the 3AP induced less- conductive Cs4PbBr6 and ammonium salts can balance the charge injection into the EML effectively. As a result, we achieved efficient PeLEDs based on thermally evaporated CsPbBr3 with a luminance of 15745 cd/m(2), current efficiency of 32 cd/A, external quantum efficiency of 8.86%, and lifetime of 3.74 h. The strategy proposed here may shed light on the development of highly efficient thermally evaporated PeLEDs.
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