Browsing by Author "Zhao, Jianlin"

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All-optically controlled slow and fast lights in graphene-coated tilted fiber Bragg grating
(2019-01-01) Wang, Yadong; Jiang, Biqiang; Das, Susobhan; Zhao, Qiang; Gan, Xuetao; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
We demonstrate all-optically controlled slow and fast lights in tilted fiber Bragg grating (TFBG) with a graphene film. By employing graphene's efficient photothermal effect, the global resonances in TFBG are shifted with slopes of 1.1 and 1.01 pm mW-1 for cladding and core modes, respectively. This enables changes of group delay and thus supports tunable fast and slow lights from -156 to 20 ps in cladding modes and up to 400 ps in core modes. Our demonstration with an all-in-fiber scheme possesses advantages, such as low-cost manufacture, simple and compact configuration, and multi-wavelength operation.
Birefringence-Induced Heterogeneous Vector Pulses in Ultrafast Fiber Lasers
(2022-10) Mao, Dong; Gao, Qun; Li, Jingyi; He, Zhiwen; Du, Yueqing; Zeng, Chao; Sun, Zhipei; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Single-mode fiber lasers are capable of supporting trapped vector solitons with two similar orthogonally polarized components, due to the delicate balance between fiber birefringence and chromatic dispersion. Here, we demonstrate that heterogeneous vector pulses (HVPs) universally exist in anomalous-dispersion and near-zero-dispersion regimes, from hybrid-structure fiber lasers composed of low- and high-birefringent fibers. The vector pulses include two distinct orthogonally polarized components, one of which is a robust pulse, while the other is a gradually attenuated wavepacket composed of terahertz- (THz) repetition-rate subpulses. Simulation and analytical results fully reproduce experimental observations and demonstrate that the robust pulse couples a fraction of its energy to the orthogonally polarized component per roundtrip at the high-birefringent fiber, forming the unique HVPs. Apart from the intriguing nonlinear dynamics, the HVP can work as a flexible workhorse for various applications, ranging from optical polarization multiplexing to THz synthesis and optical precision spectroscopy.
Chip-integrated van der Waals PN heterojunction photodetector with low dark current and high responsivity
(2022-04-20) Tian, Ruijuan; Gan, Xuetao; Li, Chen; Chen, Xiaoqing; Hu, Siqi; Gu, Linpeng; Van Thourhout, Dries; Castellanos-Gomez, Andres; Sun, Zhipei; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Two-dimensional materials are attractive for constructing high-performance photonic chip-integrated photodetectors because of their remarkable electronic and optical properties and dangling-bond-free surfaces. However, the reported chip-integrated two-dimensional material photodetectors were mainly implemented with the configuration of metal-semiconductor-metal, suffering from high dark currents and low responsivities at high operation speed. Here, we report a van der Waals PN heterojunction photodetector, composed of p-type black phosphorous and n-type molybdenum telluride, integrated on a silicon nitride waveguide. The built-in electric field of the PN heterojunction significantly suppresses the dark current and improves the responsivity. Under a bias of 1 V pointing from n-type molybdenum telluride to p-type black phosphorous, the dark current is lower than 7 nA, which is more than two orders of magnitude lower than those reported in other waveguide-integrated black phosphorus photodetectors. An intrinsic responsivity up to 577 mA W-1 is obtained. Remarkably, the van der Waals PN heterojunction is tunable by the electrostatic doping to further engineer its rectification and improve the photodetection, enabling an increased responsivity of 709 mA W-1. Besides, the heterojunction photodetector exhibits a response bandwidth of similar to 1.0 GHz and a uniform photodetection over a wide spectral range, as experimentally measured from 1500 to 1630 nm. The demonstrated chip-integrated van der Waals PN heterojunction photodetector with low dark current, high responsivity and fast response has great potentials to develop high-performance on-chip photodetectors for various photonic integrated circuits based on silicon, lithium niobate, polymer, etc.
Complete structural characterization of single carbon nanotubes by Rayleigh scattering circular dichroism
(2021-10) Yao, Fengrui; Yu, Wentao; Liu, Can; Su, Yingze; You, Yilong; Ma, He; Qiao, Ruixi; Wu, Chunchun; Ma, Chaojie; Gao, Peng; Xiao, Fajun; Zhao, Jianlin; Bai, Xuedong; Sun, Zhipei; Maruyama, Shigeo; Wang, Feng; Zhang, Jin; Liu, Kaihui
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Non-invasive, high-throughput spectroscopic techniques can identify chiral indices (n,m) of carbon nanotubes down to the single-tube level1–6. Yet, for complete characterization and to unlock full functionality, the handedness, the structural property associated with mirror symmetry breaking, also needs to be identified accurately and efficiently7–14. So far, optical methods fail in the handedness characterization of single nanotubes because of the extremely weak chiroptical signals (roughly 10−7) compared with the excitation light15,16. Here we demonstrate the complete structure identification of single nanotubes in terms of both chiral indices and handedness by Rayleigh scattering circular dichroism. Our method is based on the background-free feature of Rayleigh scattering collected at an oblique angle, which enhances the nanotube’s chiroptical signal by three to four orders of magnitude compared with conventional absorption circular dichroism. We measured a total of 30 single-walled carbon nanotubes including both semiconducting and metallic nanotubes and found that their absolute chiroptical signals show a distinct structure dependence, which can be qualitatively understood through tight-binding calculations. Our strategy enables the exploration of handedness-related functionality of single nanotubes and provides a facile platform for chiral discrimination and chiral device exploration at the level of individual nanomaterials.
Difference frequency generation in monolayer MoS2
(2020-10-14) Wang, Yadong; Ghotbi, Masood; Das, Susobhan; Dai, Yunyun; Li, Shisheng; Hu, Xuerong; Gan, Xuetao; Zhao, Jianlin; Sun, Zhipei
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Difference frequency generation has long been employed for numerous applications, such as coherent light generation, sensing and imaging. Here, we demonstrate difference frequency generation down to atomic thickness in monolayer molybdenum disulfide. By mixing femtosecond optical pulses at wavelength of 406 nm with tunable pulses in the spectral range of 1300-1520 nm, we generate tunable pulses across the spectral range of 550-590 nm with frequency conversion efficiency up to ∼2 × 10-4. The second-order nonlinear optical susceptibility of monolayer molybdenum disulfide, χ(2)eff, is calculated as ∼1.8 × 10-8 m V-1, comparable to the previous results demonstrated with second harmonic generation. Such a highly efficient down-conversion nonlinear optical process in two-dimensional layered materials may open new ways to their nonlinear optical applications, such as coherent light generation and amplification.
The dissipative Talbot soliton fiber laser
(2024-03-15) Zhang, Heze; Du, Yueqing; Zeng, Chao; Sun, Zhipei; Zhang, Yong; Zhao, Jianlin; Mao, Dong
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Talbot effect, characterized by the replication of a periodic optical field in a specific plane, is governed by diffraction and dispersion in the spatial and temporal domains, respectively. In mode-locked lasers, Talbot effect is rarely linked with soliton dynamics since the longitudinal mode spacing and cavity dispersion are far away from the self-imaging condition. We report switchable breathing and stable dissipative Talbot solitons in a multicolor mode-locked fiber laser by manipulating the frequency difference of neighboring spectra. The temporal Talbot effect dominates the laser emission state-in the breathing state when the integer self-imaging distance deviates from the cavity length and in the steady state when it equals the cavity length. A refined Talbot theory including dispersion and nonlinearity is proposed to accurately depict this evolution behavior. These findings pave an effective way to control the operation in dissipative optical systems and open branches in the study of nonlinear physics.
Giant All-Optical Modulation of Second-Harmonic Generation Mediated by Dark Excitons
(2021-08-18) Wang, Yadong; Das, Susobhan; Iyikanat, Fadil; Dai, Yunyun; Li, Shisheng; Guo, Xiangdong; Yang, Xiaoxia; Cheng, Jinluo; Hu, Xuerong; Ghotbi, Masood; Ye, Fangwei; Lipsanen, Harri; Wu, Shiwei; Hasan, Tawfique; Gan, Xuetao; Liu, Kaihui; Sun, Dong; Dai, Qing; García De Abajo, F. Javier; Zhao, Jianlin; Sun, Zhipei
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
All-optical control of nonlinear photonic processes in nanomaterials is of significant interest from a fundamental viewpoint and with regard to applications ranging from ultrafast data processing to spectroscopy and quantum technology. However, these applications rely on a high degree of control over the nonlinear response, which still remains elusive. Here, we demonstrate giant and broadband all-optical ultrafast modulation of second-harmonic generation (SHG) in monolayer transition-metal dichalcogenides mediated by the modified excitonic oscillation strength produced upon optical pumping. We reveal a dominant role of dark excitons to enhance SHG by up to a factor of ∼386 at room temperature, 2 orders of magnitude larger than the current state-of-the-art all-optical modulation results. The amplitude and sign of the observed SHG modulation can be adjusted over a broad spectral range spanning a few electronvolts with ultrafast response down to the sub-picosecond scale via different carrier dynamics. Our results not only introduce an efficient method to study intriguing exciton dynamics, but also reveal a new mechanism involving dark excitons to regulate all-optical nonlinear photonics.
Graphene Actively Mode-Locked Lasers
(2018-07) Bogusławski, Jakub; Wang, Yadong; Xue, Hui; Yang, Xiaoxia; Mao, Dong; Gan, Xuetao; Ren, Zhaoyu; Zhao, Jianlin; Dai, Qing; Soboń, Grzegorz; Sotor, Jarosław; Sun, Zhipei
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Actively mode-locked lasers offer varying degrees of flexibility for a wider range of applications than their passively modulated counterparts, due to their capability for electrically controlled ultrahigh repetition rate operation. Graphene based electrooptic modulators with unique advantages of broad operation bandwidth and ultrafast speed are suitable for light modulation in various optoelectronic applications. Here, an actively mode-locked laser with a graphene based electrooptic modulator is reported for the first time. The active mode-locking technique combined together with the intracavity nonlinear pulse shortening effect allows the generation of transform-limited 1.44 ps pulses with pulse energy of 844 pJ. The electrically controlled repetition rate of generated pulses, a key performance advantage of active mode-locking, is also demonstrated. These results provide a practical and effective approach for actively mode-locked lasers with broad operation bandwidth and compact footprint, which contributes a new way for applications of two-dimensional (2D) layered materials in ultrafast lasers.
Heteronuclear multicolor soliton compounds induced by convex-concave phase in fiber lasers
(2023-12) Zhang, Heze; Mao, Dong; Du, Yueqing; Zeng, Chao; Sun, Zhipei; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Optical solitons emerging from fiber resonators generally possess similar properties that hinge on the system parameters. However, the generation of wavepackets composed of dissimilar solitons within the same laser cavity is still challenging in ultrafast lasers. Here, we report on heteronuclear multicolor soliton compounds composed of chirp-free conventional solitons and chirped dissipative solitons, by introducing convex-concave frequency phases in mode-locked fiber lasers. In spite of different lasing wavelengths, the dissipative solitons always overlap with the conventional solitons, giving birth to trains of modulated wavepackets. The resonant sidebands of two types of solitons follow from the same phase-matching principle dominated by the absolute value of cavity dispersion. Simulations fully substantiate the experimental results, confirming that the overlapping of two solitons is dominated by the co-action of saturable absorption and group-delay compensation. It is demonstrated that the phase-managed dissipative system is capable of supporting multicolor soliton compounds with distinct properties, offering an effective platform to reveal the interaction of dissimilar nonlinear wavepackets.
Low‐Power Continuous‐Wave Second Harmonic Generation in Semiconductor Nanowires
(2018-10) Yuan, Qingchen; Fang, Liang; Yang, He; Gan, Xuetao; Khayrudinov, Vladislav; Lipsanen, Harri; Sun, Zhipei; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Semiconductor nanowires (NWs) are promising for realizing various on‐chip nonlinear optical devices, due to their nanoscale lateral confinement and strong light–matter interaction. However, high‐intensity pulsed pump lasers are typically needed to exploit their optical nonlinearity because light couples poorly with nanometric‐size wires. Here, microwatts continuous‐wave light pumped second harmonic generation (SHG) in AlGaAs NWs is demonstrated by integrating them with silicon planar photonic crystal cavities. Light–NW coupling is enhanced effectively by the extremely localized cavity mode at the subwavelength scale. Strong SHG is obtained even with a continuous‐wave laser excitation with a pump power down to urn:x-wiley:18638880:media:lpor201800126:lpor201800126-math-0001W, and the cavity‐enhancement factor is estimated around 150. Additionally, in the integrated device, the NW's SHG is more than two orders of magnitude stronger than third harmonic generations in the silicon slab, though the NW only couples with less than 1% of the cavity mode. This significantly reduced power requirement of NW's nonlinear frequency conversion would promote NW‐based building blocks for nonlinear optics, especially in chip‐integrated coherent light sources, entangled photon pairs and signal processing devices.
Measurement of complex optical susceptibility for individual carbon nanotubes by elliptically polarized light excitation
(2018-12-01) Yao, Fengrui; Liu, Can; Chen, Cheng; Zhang, Shuchen; Zhao, Qiuchen; Xiao, Fajun; Wu, Muhong; Li, Jiaming; Gao, Peng; Zhao, Jianlin; Bai, Xuedong; Maruyama, Shigeo; Yu, Dapeng; Wang, Enge; Sun, Zhipei; Zhang, Jin; Wang, Feng; Liu, Kaihui
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The complex optical susceptibility is the most fundamental parameter characterizing light-matter interactions and determining optical applications in any material. In one-dimensional (1D) materials, all conventional techniques to measure the complex susceptibility become invalid. Here we report a methodology to measure the complex optical susceptibility of individual 1D materials by an elliptical-polarization-based optical homodyne detection. This method is based on the accurate manipulation of interference between incident left- (right-) handed elliptically polarized light and the scattering light, which results in the opposite (same) contribution of the real and imaginary susceptibility in two sets of spectra. We successfully demonstrate its application in determining complex susceptibility of individual chirality-defined carbon nanotubes in a broad optical spectral range (1.6–2.7 eV) and under different environments (suspended and in device). This full characterization of the complex optical responses should accelerate applications of various 1D nanomaterials in future photonic, optoelectronic, photovoltaic, and bio-imaging devices.
Metasurface for oscillatory spin splitting along the optical path
(2022-09-01) Li, Yu; Fan, Xinhao; Guo, Xuyue; Zhang, Yi; Liu, Sheng; Wei, Bingyan; Wen, Dandan; Li, Peng; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Spin splitting of light originates from the interplay between the polarization and spatial degrees of freedom as a fundamental constituent of the emerging spin photonics, providing a prominent pathway for manipulating photon spin and developing exceptional photonic devices. However, previously relevant devices were mainly designed for routing monotonous spin splitting of light. Here, we realize an oscillatory spin splitting of light via metasurface with two channel Pancharatnam–Berry phases. For the incidence of a linearly polarized light, the concomitant phases arising from opposite spin states transition within pathways of the metasurface induce lateral spin splitting of light with alternately changed transport direction during beam guiding. We demonstrate the invariance of this phenomenon with an analogous gauge transformation. This work provides a new insight on steering the photon spin and is expected to explore a novel guiding mechanism of relativistic spinning particles, as well as applications of optical trapping and chirality sorting.
Mode couplings of a semiconductor nanowire scanning across a photonic crystal nanocavity
(2019-06-10) Yuan, Qingchen; Fang, Liang; Zhao, Qiang; Wang, Yadong; Mao, Bo; Khayrudinov, Vladislav; Lipsanen, Harri; Sun, Zhipei; Zhao, Jianlin; Gan, Xuetao
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The position-dependent mode couplings between a semiconductor nanowire (NW) and a planar photonic crystal (PPC) nanocavity are studied. By scanning anNWacross a PPC nanocavity along the hexagonal lattice's Γ -M and M - K directions, the variations of resonant wavelengths, quality factors, and mode volumes in both fundamental and second-order resonant modes are calculated, implying optimal configurations for strong mode-NW couplings and light-NW interactions. For the fundamental (second-order) resonant mode, scanning anNWalong theM- K (Γ - M) direction is preferred, which supports stronger light-NW interactions with larger NW-position tolerances and higher quality factors simultaneously. The simulation results are confirmed experimentally with good agreements.
A MoSe2/WSe2 Heterojunction-Based Photodetector at Telecommunication Wavelengths
(2018-11-21) Xue, Hui; Wang, Yadong; Dai, Yunyun; Kim, Wonjae; Jussila, Henri; Qi, Mei; Susoma, Jannatul; Ren, Zhaoyu; Dai, Qing; Zhao, Jianlin; Halonen, Kari; Lipsanen, Harri; Wang, Xiaomu; Gan, Xuetao; Sun, Zhipei
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
van der Waals (vdW) heterojunctions enable arbitrary combinations of different layered semiconductors with unique band structures, offering distinctive band engineering for photonic and optoelectronic devices with new functionalities and superior performance. Here, an interlayer photoresponse of a few-layer MoSe2/WSe2 vdW heterojunction is reported. With proper electrical gating and bias, the heterojunction exhibits high-sensitivity photodetection with the operation wavelength extended up to the telecommunication band (i.e. 1550 nm). The photoresponsivity and normalized photocurrent-to-dark current ratio reach up to 127 mA W−1 and 1.9 × 104 mW−1, respectively. The results not only provide a promising solution to realize high-performance vdW telecommunication band photodetectors, but also pave the way for using sub-bandgap engineering of two-dimensional layered materials for photonic and optoelectronic applications.
Nanowire-assisted microcavity in a photonic crystal waveguide and the enabled high-efficiency optical frequency conversions
(2020-10-22) Gu, Linpeng; Fang, Liang; Yuan, Qingchen; Gan, Xuetao; Hao, Yang; Zhang, Xutao; Li, Juntao; Fang, Hanlin; Khayrudinov, Vladislav; Lipsanen, Harri; Sun, Zhipei; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
We report an indium phosphide nanowire (NW)-induced cavity in a silicon planar photonic crystal (PPC) waveguide to improve the light–NW coupling. The integration of NW shifts the transmission band of the PPC waveguide into the mode gap of the bare waveguide, which gives rise to a microcavity located on the NW section. Resonant modes with 푄 factors exceeding 103 are obtained. Leveraging on the high density of the electric field in the microcavity, the light–NW interaction is enhanced strongly for efficient nonlinear frequency conversion. Second-harmonic generation and sum-frequency generation in the NW are realized with a continuous-wave pump laser in a power level of tens of microwatts, showing a cavity-enhancement factor of 112. The hybrid integration structure of NW-PPC waveguide and the self-formed microcavity not only opens a simple strategy to effectively enhance light–NW interactions, but also provides a compact platform to construct NW-based on-chip active devices.
Phase-matching-induced near-chirp-free solitons in normal-dispersion fiber lasers
(2022-01-25) Mao, Dong; He, Zhiwen; Zhang, Yusong; Du, Yueqing; Zeng, Chao; Yun, Ling; Luo, Zhichao; Li, Tijian; Sun, Zhipei; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Direct generation of chirp-free solitons without external compression in normal-dispersion fiber lasers is a long-term challenge in ultrafast optics. We demonstrate near-chirp-free solitons with distinct spectral sidebands in normal-dispersion hybrid-structure fiber lasers containing a few meters of polarization-maintaining fiber. The bandwidth and duration of the typical mode-locked pulse are 0.74 nm and 1.95 ps, respectively, giving the time-bandwidth product of 0.41 and confirming the near-chirp-free property. Numerical results and theoretical analyses fully reproduce and interpret the experimental observations, and show that the fiber birefringence, normal-dispersion, and nonlinear effect follow a phase-matching principle, enabling the formation of the near-chirp-free soliton. Specifically, the phase-matching effect confines the spectrum broadened by self-phase modulation and the saturable absorption effect slims the pulse stretched by normal dispersion. Such pulse is termed as birefringence-managed soliton because its two orthogonal-polarized components propagate in an unsymmetrical “X” manner inside the polarization-maintaining fiber, partially compensating the group delay difference induced by the chromatic dispersion and resulting in the self-consistent evolution. The property and formation mechanism of birefringence-managed soliton fundamentally differ from other types of pulses in mode-locked fiber lasers, which will open new research branches in laser physics, soliton mathematics, and their related applications.
Soliton metamorphosis dynamics in ultrafast fiber lasers
(2021-05-17) He, Zhiwen; Du, Yueqing; Zeng, Chao; Jiang, Biqiang; Mao, Dong; Sun, Zhipei; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The transitions from the incoherent noise to the coherent soliton have been fully revealed in ultrafast lasers. However, the soliton transformation between different coherent states, termed as soliton metamorphosis, remains an attractive yet uncharted territory. Here, we reveal the ultrafast dynamics of the soliton metamorphosis via single-shot spectroscopy in a specially designed fiber laser capable of emitting fast-switchable dissipative solitons and stretched pulses. It is demonstrated that the soliton metamorphosis is a consecutive evolution process including the self-phase modulation stage, pulse split stage, and transient stretched pulse stage. Particularly, the long-period pulse breathing and the spectral period doubling appear in the forepart and middle part of the last stage. The metamorphosis dynamics and soliton properties are substantiated by numerical simulation based on a three-step model. This work not only unveils the transient evolution physics of the pulse in soliton metamorphosis, but also provides a simple and effective way to control operations of ultrafast lasers.
Strong Second Harmonic Generation from Bilayer Graphene with Symmetry Breaking by Redox-Governed Charge Doping
(2022-05-24) Zhang, Mingwen; Han, Nannan; Wang, Jing; Zhang, Zhihong; Liu, Kaihui; Sun, Zhipei; Zhao, Jianlin; Gan, Xuetao
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Missing second-order nonlinearity in centrosymmetric graphene overshadows its intriguing optical attribute. Here, we report redox-governed charge doping could effectively break the centrosymmetry of bilayer graphene (BLG), enabling a strong second harmonic generation (SHG) with a strength close to that of the well-known monolayer MoS2. Verified from control experiments with in situ electrical current annealing and electrically gate-controlled SHG, the required centrosymmetry breaking of the emerging SHG arises from the charge-doping on the bottom layer of BLG by the oxygen/water redox couple. Our results not only reveal that charge doping is an effective way to break the inversion symmetry of BLG despite its strong interlayer coupling but also indicate that SHG spectroscopy is a valid technique to probe molecular doping on two-dimensional materials.
Synchronized multi-wavelength soliton fiber laser via intracavity group delay modulation
(2021-11-18) Mao, Dong; Wang, Huaqiang; Zhang, Heze; Zeng, Chao; Du, Yueqing; He, Zhiwen; Sun, Zhipei; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Locking of longitudinal modes in laser cavities is the common path to generate ultrashort pulses. In traditional multi-wavelength mode-locked lasers, the group velocities rely on lasing wavelengths due to the chromatic dispersion, yielding multiple trains of independently evolved pulses. Here, we show that mode-locked solitons at different wavelengths can be synchronized inside the cavity by engineering the intracavity group delay with a programmable pulse shaper. Frequency-resolved measurements fully retrieve the fine temporal structure of pulses, validating the direct generation of synchronized ultrafast lasers from two to five wavelengths with sub-pulse repetition-rate up to similar to 1.26 THz. Simulation results well reproduce and interpret the key experimental phenomena, and indicate that the saturable absorption effect automatically synchronize multi-wavelength solitons in despite of the small residual group delay difference. These results demonstrate an effective approach to create synchronized complex-structure solitons, and offer an effective platform to study the evolution dynamics of nonlinear wavepackets.
Ultrafast all-fiber based cylindrical-vector beam laser
(2017-01-09) Mao, Dong; Feng, Tianxian; Zhang, Wending; Lu, Hua; Jiang, Yajun; Li, Peng; Jiang, Biqiang; Sun, Zhipei; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Cylindrical-vector beams (CVBs) with axial symmetry in polarization and field intensity are gathering increasing attention from fundamental research to practical applications. However, a majority of the CVBs are generated by modulating light beams in free space, and the temporal durations are far away from the ultrafast regime. Here, an ultrafast all-fiber based CVB laser is demonstrated via intermodal coupling in two mode fibers. In the temporal domain, chirp-free pulses are formed with combined actions of the ultrafast saturable absorption, self-phase modulation, and anomalous dispersion. In the spatial domain, the lateral offset splicing technique and a two mode fiber Bragg grating are adopted to excite and extract CVBs, respectively. The ultrafast CVB has an annular profile with a duration of 6.87 ps and a fundamental repetition rate of 13.16 MHz, and the output polarization status is switchable between radially and azimuthally polarized states. This all-fiber-based ultrafast CVB laser is a simple, low-cost source for diversified applications of nanoparticle manipulation, high-resolution imaging, material processing, spatiotemporal nonlinear optics, etc.