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344 results on '"Liu Yan-Ge"'

1. Simultaneous generation of first- to fourth-order OAM modes based on a cascaded preset-twist long-period fiber grating

Author

Chang Wenzhe, Liu Yan-ge, Shi Zekun, Guo Huiyi, Wang Xin, Wang Pan, and Wang Zhi

Subjects
orbital angular momentum mode, long-period fiber grating, mode converter, Physics, QC1-999
Abstract

We propose and demonstrate the simulation and fabrication of an all-fiber orbital angular momentum (OAM) mode converter capable of generating first- to fourth-order modes simultaneously, which is realized by inscribing a cascaded preset-twist long-period fiber grating (CPT-LPFG) in a six-mode fiber utilizing a CO2 laser. A new segmented Runge–Kutta method is proposed to simulate the preset-twist long-period fiber gratings. By calculating the twist angle and relative coupling coefficient for each pitch and then solving the coupled mode equations utilizing the Runge–Kutta algorithm. The simulation illustrates that the preset-twist method significantly improves the coupling coefficient of higher-order modes, thereby reducing coupling difficulty. In the experiment, by twisting the fiber at an angle of 1080° and fabricating cascaded gratings with periods of 745 μm, 310 μm, 204 μm, and 146 μm, it is feasible to generate first- to fourth-order OAM modes simultaneously, at wavelengths of 1635 nm, 1548 nm, 1460 nm, and 1334 nm, respectively. The insertion loss is less than 1 dB, and the mode purity is over 90 %. To the best of our knowledge, this is the first time that first- to fourth-order OAM modes are simultaneously generated utilizing a single long-period fiber grating.

Published
2024
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2. Broadband saturable absorption in germanene for mode-locked Yb, Er, and Tm fiber lasers

Author

Wang Qingbo, Kang Jianlong, Wang Pan, He Jiangyong, Liu Yicong, Wang Zhi, Zhang Han, and Liu Yan-ge

Subjects
broadband saturable absorber, fiber laser, germanene, mode-locked, Physics, QC1-999
Abstract

Passively mode-locked lasers have been widely investigated as one of the effective methods to obtain ultrashort pulses. As an important part of passively mode-locked fiber lasers, the exploration of 2D material-based saturable absorber has become one of the hotspots in ultrafast photonics in recent years. Germanene, a novel 2D Dirac material, with ultrafast optical response and broadband optical absorption, is a promising alternative material for saturable absorber in mode-locked fiber lasers. In this paper, germanium nanosheets are prepared via liquid-phase exfoliated method, with the saturable absorption property systematically characterized in three major wavebands of the near-infrared region. The generation of ultrashort pulses based on germanene saturable absorber in fiber lasers is further realized, in a broad waveband (1000 nm) centered at 1061.1, 1559.3 and 1883.5 nm, respectively. In addition, noise-like pulses operation with central wavelength of 1558.6 nm is also obtained, and the formation of rogue waves is further demonstrated via statistical analysis. To the best of our knowledge, this is the first experimental verification of the broadband saturable absorption property of germanene-based devices, covering three major fiber laser wavelengths from 1.0 to 2.0 μm.

Published
2022
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3. Controllable all-fiber generation/conversion of circularly polarized orbital angular momentum beams using long period fiber gratings

Author

Han Ya, Liu Yan-Ge, Wang Zhi, Huang Wei, Chen Lei, Zhang Hong-Wei, and Yang Kang

Subjects
fiber gratings, higher order linearly polarized modes, orbital angular momentum beams, Physics, QC1-999
Abstract

Mode-division multiplexing (MDM) is a promising technology for increasing the data-carrying capacity of a single few-mode optical fiber. The flexible mode manipulation would be highly desired in a robust MDM network. Recently, orbital angular momentum (OAM) modes have received wide attention as a new spatial mode basis. In this paper, we firstly proposed a long period fiber grating (LPFG) system to realize mode conversions between the higher order LP core modes in four-mode fiber. Based on the proposed system, we, for the first time, demonstrate the controllable all-fiber generation and conversion of the higher order LP core modes to the first and second order circularly polarized OAM beams with all the combinations of spin and OAM. Therefore, the proposed LPFG system can be potentially used as a controllable higher order OAM beam switch and a physical layer of the translating protocol from the conventional LP modes communication to the OAM modes communication in the future mode carrier telecommunication system and light calculation protocols.

Published
2018
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10. Dynamics of Pulsating Dissipative Solitons

Author

Wang, Xiaoqing, He, Jiangyong, Mao, Baiwei, Wang, Zhi, Liu, Yan-ge, Lotsch, H.K.V., Founding Editor, Rhodes, William T., Editor-in-Chief, Adibi, Ali, Series Editor, Asakura, Toshimitsu, Series Editor, Hänsch, Theodor W., Series Editor, Krausz, Ferenc, Series Editor, Masters, Barry R., Series Editor, Midorikawa, Katsumi, Series Editor, Venghaus, Herbert, Series Editor, Weber, Horst, Series Editor, Weinfurter, Harald, Series Editor, Kobayashi, Kazuya, Series Editor, Markel, Vadim, Series Editor, and Ferreira, Mário F. S., editor

Published
2022
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15. Wavelength Insensitive Mode Selective Coupler Based on Ultra-Wideband Resonant Effect

Author

Guo, Huiyi, Liu, Yan-Ge, Chen, Liang, Wang, Xin, Zhang, Ziyang, and Wang, Zhi

Abstract

We report on an ultra-wideband resonance effect between LP01 mode and LP21 mode in a fused-biconical taper mode selective coupler. The dispersion characteristics of the LP01 and LP21 modes are changed by tapered fibers, and achieved resonance over a large range of over 1000 nm. Based on this effect, we designed and manufactured a super wide-band fused biconical LP21 mode selective coupler, which covers the S+C+L band with an insertion loss flatness of better than 0.17 dB and a minimum insertion loss of 0.16 dB. A broadband and flat mode converter facilitates cost-effective integration of wavelength division multiplexing systems and space division multiplexing systems.

Published
2024
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31. Transition Between Quadratic and Quartic Solitons With OAM Modes in Passive Driven Fiber Resonator

Author

Shi, Zhifeng, Wang, Pan, Sun, Shijie, Wang, Qingbo, Wang, Zhi, and Liu, Yan-Ge

Abstract

Solitons are particular wave packets that can propagate and maintain stable shape by complex balance between dispersion and nonlinear effects. Very recently, the new concept of pure-quartic soliton has been widely discussed due to its extraordinary energy scaling law, arising from the interaction between quartic dispersion and nonlinear Kerr effects. In our work, we numerically investigate the nonlinear dynamics of pure-quartic solitons with orbital angular momentum (OAM) in passive driven fiber resonator. The dual-concentric Germania-doped ring-core fiber (GRF) is specially designed to support OAM modes in the resonator. Since different OAM modes are related to different dispersion conditions, the transition between conventional quadratic soliton and pure-quartic soliton can be achieved by changing the OAM mode orders of the driving continuous wave source. Our work provides a promising method to control the dispersion for soliton formation through transverse structured mode conversion, and might benefit the investigation of spatio-temporal solitons in the future.

Published
2024
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32. Accurate and Noise-Robust Mode Decomposition by Analyzing the Intensity Distribution of a Few-Mode Ring Core Fiber

Author

Shi, Zekun, Mao, Baiwei, Wang, Zhi, and Liu, Yan-Ge

Abstract

Mode decomposition is a fundamental issue in applications that exploit few-mode fibers. With a prior knowledge of eigenmode field distribution, the amplitudes and phases of each spatial mode can be recovered. In this article, we propose a simple and accurate Fourier-transform-assisted mode decomposition method by only analyzing the intensity distribution of a few-mode fiber output. Numerical demonstration and experimental verification are executed in a few-mode ring core fiber supporting four mode groups. Simulation results of 1000 random samples show the proposed method's superiority in accuracy and noise immunity. The correlation of preset and reconstructed intensity distributions is as high as 0.9999 in the noiseless condition. The amplitudes of fiber modes can still be recovered when the signal-to-noise ratio is as low as 5 dB. In the experiment, the average correlation between the measured and reconstructed intensity distributions for 300 randomly captured pictures is about 0.9906.

Published
2024
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33. The Generation of Ultrahigh Repetition-Rate OAM Frequency Combs in Dual-Concentric Germania-Doped Ring-Core Fiber

Author

Wang, Pan, Shi, Zhifeng, Wang, Qingbo, He, Jiangyong, Wang, Zhi, and Liu, Yan-Ge

Abstract

We theoretically demonstrate, for the first time to the best of our knowledge, the orbital angular momentum (OAM) frequency combs induced by dissipative Faraday instability (DFI) mechanism in a 2-μm waveband Mamyshev oscillator. Dual-concentric Germania-doped ring-core fibers are specially designed with flat normal dispersion curves for different OAM modes, inhibiting the Benjamin-Feir instability and facilitating phase matching conditions for broadband frequency comb generation. The frequency comb tooth spacing scales up to ∼100 GHz, which matches well with the Floquet linear stability analysis by Ikeda map. Our investigations might benefit the development of OAM frequency combs for a variety of further applications including communication.

Published
2024
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