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92 results on '"He, Zhiwen"'

78. Physical vapor deposition of large-scale PbSe films and its applications in pulsed fiber lasers.

Author

Gao, Qun, Yang, Hao, Hu, Cuichen, He, Zhiwen, Lu, Hua, Zhang, Wending, Mao, Dong, Mei, Ting, and Zhao, Jianlin

Subjects
PHYSICAL vapor deposition, Q-switched lasers, MODE-locked lasers, PULSED lasers, OPTICAL modulators, LEAD selenide crystals, POLYVINYL alcohol, OPTICAL detectors
Abstract

Lead selenide (PbSe) is a new emerging semiconductor with layer-dependent bandgap that has attracted much interest due to its high infrared response and good environmental stability. We have prepared large-scale PbSe films with the area of 7 cm2 and thickness of 25 nm based on physical vapor deposition approach at 160°C. The PbSe films exhibit saturable absorption property at 1.55 μm and a polarization-sensitive saturable absorber is obtained by growing PbSe on D-shaped fiber. Single-pulse with the duration of 490 fs is generated at the pump of 12 mW and the mode-locking operation is maintained at the pump of 1500 mW, indicating the high damage threshold of the D-shaped fiber based saturable absorber. Two polarization-insensitive saturable absorbers are achieved by depositing PbSe on fiber facet and polyvinyl alcohol film, respectively. For fiber facet (polyvinyl alcohol film) based saturable absorber, the repetition rate of Q-switched pulses increases from 8.6 (16.3) kHz to 45.4 (59.2) kHz while the duration decreases from 7.92 (12) μs to 2.06 (3.12) μs by tuning the pump from 15 mW to 90 (60) mW. Such large-scale PbSe films possess features of low cost and high modulation ability, and can find important applications in infrared optical modulators and detectors. [ABSTRACT FROM AUTHOR]

Published
2020
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79. Partial difference sets and amorphic Cayley schemes in non‐abelian 2‐groups.

Author

Feng, Tao, He, Zhiwen, and Chen, Yu Qing

Subjects
*AUTOMORPHISM groups, *DIFFERENCE sets, *AUTOMORPHISMS, *ABELIAN groups, *MAGIC squares, *REGULAR graphs
Abstract

In this paper, we consider regular automorphism groups of graphs in the RT2 family and the Davis‐Xiang family and amorphic abelian Cayley schemes from these graphs. We derive general results on the existence of non‐abelian regular automorphism groups from abelian regular automorphism groups and apply them to the RT2 family and Davis‐Xiang family and their amorphic abelian Cayley schemes to produce amorphic non‐abelian Cayley schemes. [ABSTRACT FROM AUTHOR]

Published
2020
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90. Passively Q-switched cylindrical vector laser based on a black phosphorus saturable absorber

Author

He, Zhiwen, Zheng, Yang, Liu, Hongyan, Li, Mingkun, Lu, Hua, Zhang, Heze, Feng, Qingliang, and Mao, Dong

Abstract

We demonstrate an all-fiber Q-switched cylindrical vector laser based on a black phosphorus saturable absorber and a transverse mode converter. The saturable absorber is prepared by incorporating the polyvinyl alcohol with anti-oxidized black phosphorus nanosheets exfoliated in aqueous poly(dimethyldiallyl ammonium chloride) solution. The mode converter is composed of a tapered two-mode fiber and a single-mode fiber, and it can excite switchable azimuthally and radially polarized beams by modulating the input polarization. By enhancing the pump power from 64.68 to 174.82 mW, the repetition rate of the Q-switched azimuthally/radially polarized laser enlarges from 16.72/19.25 to 30.71/37.82 kHz.

Published
2019

91. CaY@C 2 n : Exploring Molecular Qubits with Ca-Y Metal-Metal Bonds.

Author

Qiu J, Abella L, Du X, Cao Z, He Z, Meng Q, Yan Y, Poblet JM, Sun L, Rodríguez-Fortea A, and Chen N

Abstract

Metal-metal bonding is crucial in chemistry for advancing our understanding of the fundamental aspects of chemical bonds. Metal-metal bonds based on alkaline-earth (Ae) elements, especially the heavier Ae elements (Ca, Sr, and Ba), are rarely reported due to their high electropositivity. Herein, we report two heteronuclear di-EMFs CaY@ C s (6)-C 82 and CaY@ C 2 v (5)-C 80 , which contain unprecedented single-electron Ca-Y metal-metal bonds. These compounds were characterized by single-crystal X-ray crystallography, electron paramagnetic resonance (EPR) spectroscopy, and DFT calculations. The crystallographic study of CaY@ C s (6)-C 82 shows that Ca and Y are successfully encapsulated into the carbon cage with a Ca-Y distance of 3.691 Å. The CW-EPR study of both CaY@ C s (6)-C 82 and CaY@ C 2 v (5)-C 80 exhibits a doublet, suggesting the presence of an unpaired electron located between Ca and Y. The combined experimental and theoretical results confirm the presence of a Ca-Y single-electron metal-metal bond with substantial covalent interaction, attributed to significant overlap between the 4s4p orbitals of Ca and the 5s5p4d orbitals of Y. Furthermore, pulse EPR spectroscopy was used to investigate the quantum coherence of the electron spin within this bond. The unpaired electron, characterized by its s orbital nature, is effectively protected by the carbon cage, resulting in efficient suppression of both spin-lattice relaxation and decoherence. CaY@ C s (6)-C 82 behaves as an electron spin qubit, displaying a maximum decoherence time of 7.74 μs at 40 K. This study reveals an unprecedented Ae-rare-earth metal-metal bond stabilized by the fullerene cages and elucidates the molecular qubit properties stemming from their unique bonding character, highlighting their potential in quantum information processing applications.

Published
2024
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92. Broadband polarization-insensitive saturable absorption of Fe 2 O 3 nanoparticles.

Author

Mao D, Cui X, He Z, Lu H, Zhang W, Wang L, Zhuang Q, Hua S, Mei T, and Zhao J

Abstract

The synthesis and functionalization of transition-metal oxides are one of the most active research areas in advanced materials. As a typical transition-metal oxide, iron oxide has been widely used in lithium-ion batteries, gas sensors, and for water treatment. Herein, we synthesized Fe 2 O 3 nanoparticles by a co-precipitation method that is inexpensive and non-toxic. The Fe 2 O 3 nanoparticles exhibited broadband saturable absorption. Furthermore, thin Fe 2 O 3 polyvinyl alcohol films were prepared to realize Q-switched operations in a ytterbium-doped fibre laser, an erbium-doped fibre laser, and a thulium-doped fibre laser. Attributed to the polarization-insensitive feature of the saturable absorber, Q-switched cylindrical vector beams were also generated based on mode coupling and selection in two-mode fibre lasers. Such Fe 2 O 3 nanoparticles show great promise for use in Q-switching applications of infrared fibre lasers and cylindrical vector lasers.

Published
2018
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