- 标题
- 摘要
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- 实验方案
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Multiplexed ultrafast fiber laser emitting multi-state solitons
摘要： Ultrafast fiber lasers have been serving as an ideal playground for spreading the extensive industrial applications and exploring the optics nonlinear dynamics. Here, we report a bidirectional fiber laser scheme for validating the possibility of a multiplexed laser system, which is passively mode-locked by the nonlinear polarization rotation (NPR) technique. In particular, the proposed fiber laser consists of one main cavity and two counter-propagating branches with different dispersion distributions. Thus, different formation mechanisms are introduced into the lasing oscillator. Consequently, stable conventional solitons (CSs) and dissipative solitons (DSs) are respectively formed in the clockwise (CW) and counterclockwise (CCW) directions of the same lasing oscillator. Moreover, attributing to the strong birefringence filtering effect, the wavelength selection mechanism is induced. Through the proper management of intra-cavity birefringence, wideband wavelength tuning and switchable multi-wavelength operations are experimentally observed. The central wavelength of CS can be continuously tuned from 1560 nm to 1602 nm. Additionally, the evolution process of different multi-wavelength operations is also elucidated. Benefiting from this multiplexed laser scheme, bidirectional lasing oscillation, multi-state soliton emission, wavelength tuning and multi-wavelength operations are synchronously realized in a single laser cavity. To the best of our knowledge, it is the first time for such a multiplexed fiber laser has been reported. The results provide information for multifunctional ultrafast fiber laser system, which is potentially set for telecommunications, fiber sensing and optics signal processing, etc.
关键词： multi-wavelength operations,nonlinear polarization rotation,wavelength tuning,Ultrafast fiber lasers,dissipative solitons,conventional solitons
更新于2025-11-28 14:24:03
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A Pilot Symbols Aided Adaptive Kalman Filter for Joint Carrier Phase and Polarization Tracking in Coherent Optical System
摘要： A joint compensation scheme based on pilot symbols aiding adaptive Kalman filter (AKF) for phase noise and polarization cross-talk is proposed and investigated via numerical simulation and experimental demonstration. In the proposed scheme, the optimizing parameter Q is adaptively adjusted according to signal parameters or channel conditions. This improvement avoids the drawback of conventional extended Kalman filter (EKF), and its performance is strongly dependent on Q. Another improvement is that the convergence speed of AKF is improved. Pilot quadrature phase shift keyin (QPSK) symbols are inserted into 16 quadrature amplitude modulation (QAM) signals periodically. Besides accelerating convergence speed, the employment of pilot symbols also improves the tracking capability of AKF. The format ratio between pilot symbols and payload symbols is suggested under different system environments, for instance, optical signal-to-noise rate, polarization rotation frequency drift rate, and laser linewidth. With the proposed scheme, it has excellent tolerance to initial parameter Q and dramatically improves the performances in convergence speed, polarization rotation frequency drift rate tracking, and carrier phase recovery. Both the numerical simulation and experimental demonstration achieve convergence improvement for around 40 times than the original AKF. Additionally, the improvements in tracking ability are also demonstrated.
关键词： dynamic polarization rotation,pilot aided adaptive Kalman filter,phase noise,coherent optical communication
更新于2025-09-23 15:22:29
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Ferroelectric Polarization Rotation in Order-Disorder-Type LiNbO3 Thin Films
摘要： The direction of ferroelectric polarization is prescribed by the symmetry of the crystal structure. Therefore, rotation of the polarization direction is largely limited, despite the opportunity it offers in understanding important dielectric phenomena such as piezoelectric response near the morphotropic phase boundaries and practical applications such as ferroelectric memory. In this study, we report the observation of continuous rotation of ferroelectric polarization in order-disorder-type LiNbO3 thin films. The spontaneous polarization could be tilted from an out-of-plane to an in-plane direction in the thin film by controlling the Li vacancy concentration within the hexagonal lattice framework. Partial inclusion of monoclinic-like phase is attributed to the breaking of macroscopic inversion symmetry along different directions and the emergence of ferroelectric polarization along the in-plane direction.
关键词： second harmonic generation,vacancy engineering,spatial inversion symmetry breaking,ferroelectric polarization rotation,LiNbO3 thin films
更新于2025-09-23 15:21:21
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Wave plate-dependent lasing regimes transitions in an all-normal-dispersion fiber laser mode-locked by nonlinear polarization rotation
摘要： We address the transitions between three different working regimes of an all-normal-dispersion pulsed fiber laser, mode-locked by nonlinear polarization rotation (NPR). In particular, we investigate numerically the dynamics and study in details the transitions induced by solely rotating the cavity wave plates. We analyze the phemomenon by putting forward a model for all-normal-dispersion NPR-moded-locked fiber laser, based on the coupled Ginzburg-Landau equations and Jones matrix. Numerical results show that depending on the values of the cavity parameters, the transitions between the dissipative soliton regime and amplifier similariton one, or the transition between the dissipative soliton regime and the splitting pulse one may be realized by simply rotating the cavity wave plates. We found that the transitions are intrinsically related to the NPR mode-locking mechanism by explicitly evaluating the polarization states across the pulse at different locations of the cavity. Our numerical results are in very good agreement with experimental results reported in the relevant literature, and provide evidence that besides gain saturation and spectral filtering, the orientations of wave plates may be exploited as a suitable degree of freedom to obtain the desired pulse regimes in all-normal-dispersion fiber lasers.
关键词： Amplifier similariton,Splitting pulse,All-normal-dispersion fiber laser,Dissipative soliton,Nonlinear polarization rotation
更新于2025-09-23 15:19:57
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Wide-angle scanning circular polarization phased array based on polarization rotation technology
摘要： A wide-beam circular polarization (CP) antenna and a wide-angle scanning phased array based on novel polarization rotation reflective surface (PRRS) are proposed. The CP wide-beam pattern is obtained by the combination of the radiation wave from the patch antenna and the orthogonal reflected wave from the PRRS with a 90(cid:1) phase difference. The proposed CP wide-beam antenna obtains the patterns with the 3-dB beamwidth more than 136(cid:1) and the axial ratio (AR) beamwidth more than 132(cid:1) in the xoz-plane. Furthermore, an eight-element phased array based on the wide-beam CP antenna element is also developed. The measured results show that the main beam of the array can scan from ?65(cid:1) to 65(cid:1) with a gain fluctuation less than 3 dB and the ARs at every scanning angle less than 3 dB.
关键词： polarization rotation,phased array,wide-beam,circular polarization,wide-angle scanning
更新于2025-09-19 17:15:36
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Determination of the electric field and its Hilbert transform in femtosecond electro-optic sampling
摘要： We demonstrate time-domain sampling of mid-infrared electric ?eld transients and their conjugate counterparts exploiting the dynamical Pockels effect. To this end, the complete polarization change of few-femtosecond probe pulses is studied. An intuitive picture based on a phasor representation is established before gaining quantitative understanding in experiment and theory. In the standard version of electro-optic sampling, the electric ?eld is determined by analyzing the change of ellipticity of the probe polarization. Beyond this, we ?nd that a temporal gradient of the input electric ?eld manifests itself in a rotation of the polarization ellipsoid of the probe. The relative contribution of sum- and difference-frequency mixing processes and their spectral distribution over the near-infrared probe bandwidth are identi?ed as key aspects. If one of these processes dominates, detecting ellipticity changes and polarization rotation as a function of time delay results in two wave forms which are Hilbert transforms of each other. Such conditions may be achieved by angle phase matching in birefringent materials or spectral ?ltering of the probe after the nonlinear interaction. In this case, a static phase introduced by birefringence or re?ection at metallic mirrors results in a speci?c phase shift of both time traces with respect to the input electric ?eld. Contributions from sum- and difference-frequency generation are found to be equivalent when using electro-optic sensors with isotropic refractive index. Polarization rotations in the low- and high-frequency parts of the probe then tend to cancel out. In this limit, spurious additional phase shifts do not change the phase of the detected transients. This fact leads to a robust recovery of the carrier-envelope phase of the input wave form. Clarifying the role of imperfections of superachromatic phase retarders completes our survey on proper determination of the electric ?eld and its conjugate variable.
关键词： polarization rotation,sum-frequency generation,difference-frequency generation,electro-optic sampling,Pockels effect,mid-infrared,Hilbert transform
更新于2025-09-19 17:13:59
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - All-fiber Passively Mode-locked Femtosecond Laser Based on a Femtosecond Laser Inscribed 45° Tilted Fiber Grating
摘要： A femtosecond erbium-doped fiber laser using a novel 45° tilted fiber grating fabricated by direct femtosecond laser inscription is experimentally demonstrated. The laser generates stable short pulses with pulse width of 752 fs at 1562 nm. The experimental results demonstrate that mode locking is successfully achieved with pulse duration of 752 fs and pulse energy of 2.23 nJ. In particular, this kind of 45° TFG is capable of maintaining the strength and physical integrity of the fiber because it is not necessary to remove the fiber coating during inscription process.
关键词： nonlinear polarization rotation,Erbium-doped fiber laser,tilted fiber grating
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Improvement of soliton pulse energy in thulium-doped fiber laser
摘要： In this paper, we report a thulium-doped fiber laser based on non-polarization rotation technique. Increasing the pump power to 2500 mW and adjusting the polarization controllers, Baussian pulse with high pulse energy can be achieved. The pulse duration of de-chirped pulse is 242 fs. Due to dispersion management, most related studies are still focused on the 1 μm band, and few reports are available for the 2 μm band. By using non-polarization rotation technique, the mode-locked start-up threshold can be avoided. At the maximum pump power, the direct output power of the resonator cavity is 272.2 mW, and the corresponding single pulse energy is 1.825 nJ.
关键词： mode-locking,thulium-doped fiber laser,non-polarization rotation technique,dispersion management
更新于2025-09-16 10:30:52
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H-shaped pulse generation with tunable leading edge from a Tm-doped mode-locked fiber laser
摘要： A novel h-shaped pulse train with a tunable leading-edge (resembling a h-shaped pulse merging with a weak square pulse) is experimentally generated in a Tm-doped mode-locked fiber laser (MLFL) incorporating a 100 m highly nonlinear fiber. Through carefully adjusting the pump power and cavity polarization states, the leading-edge duration of the obtained h-shaped pulse can be widely tuned from zero (corresponding to the typical conventional h-shaped pulse train) to 567.8 ns (equivalent to the cavity roundtrip time). Our results can further facilitate understanding the intrinsic mechanism and characteristics of novel h-shaped pulse dynamics in MLFLs.
关键词： nonlinear polarization rotation,Tm-doped mode-locked fiber laser,tunable leading-edge,h-shaped pulse,highly nonlinear fiber
更新于2025-09-16 10:30:52
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Dual-Band Frequency Selective Surface on Aperture-Coupled Patch Resonators with Different Polarization Rotation
摘要： In this letter, a dual-band frequency selective surface (FSS) based on aperture-coupled patch resonators is proposed to achieve different angles of polarization rotation, that is, 90o and 0o. The dual-band response is achieved by periodically arranging two independent sub-elements consisting of back-to-back patch resonators with coupling apertures etched on the middle metallic layer. Herein, the first passband is realized by the crossed patch resonators with a pair of rectangular apertures etched beneath the edges of the crossed patches. It can produce 180o phase difference between the two orthogonal components of a linearly polarized (LP) incident wave oriented to the diagonal of the FSS elements, thus rotating the incident polarization to its orthogonal one in this first passband. The second passband is caused by the square patch resonators with crossed apertures etched beneath the center of the square patches, thereby maintaining the incident polarization unchanged in this second passband. The operation principle is then extensively analyzed and discussed. To validate the design concept, the proposed FSS is designed, fabricated, and measured. Good agreement between the measured and simulated results is achieved to reveal the attractive dual-band and dual-polarization features of the proposed FSS.
关键词： Dual-band,aperture-coupled patch resonators,polarization rotation,frequency selective surfaces
更新于2025-09-16 10:30:52