The fiber specklegram sensor (FSS) shows potential for mechanical parameter measurement, yet simultaneous displacement and torsion sensing remains unexplored. Here, a coupled-mode-theory-based model elucidating torsion-i...The fiber specklegram sensor (FSS) shows potential for mechanical parameter measurement, yet simultaneous displacement and torsion sensing remains unexplored. Here, a coupled-mode-theory-based model elucidating torsion-induced specklegram evolution is developed, and an efficient algorithm is devised to determine specklegram rotation angles. Experiments demonstrate that within a defined torsion range, the rotation angle varies linearly with torsion while specklegram morphology remains invariant, which is confirmed to be affected by off-axis offset, fiber length, and core diameter. Beyond this range, a hybrid framework integrating Laplacian eigenmaps with a particle swarm optimization-enhanced neural network enables torsion measurement. Simultaneous displacement and torsion sensing was achieved within the dual-output framework, and the potential for decoding multiple displacement and torsion stimuli was first confirmed in FSS. The system surpasses the existing similar fiber sensors in terms of displacement range and torsional resolution and first demonstrates FSS's extrapolation ability.
In the strongly nonlocal regime, controllable propagation of arbitrary partially coherent spatiotemporal wave packets is achieved by constructing general solutions of the (3 + 1)-dimensional nonlinear Schrödinger equatio...In the strongly nonlocal regime, controllable propagation of arbitrary partially coherent spatiotemporal wave packets is achieved by constructing general solutions of the (3 + 1)-dimensional nonlinear Schrödinger equation and tailoring the initial pulse. The three-dimensional intensity distribution and multi-parameter control of spatiotemporal cosine-Gaussian dual-layer twisted Laguerre Gaussian Schell-model array wave packets with array phase are further investigated. Results show that the peak intensity exhibits pronounced spatiotemporal correlations; the chirp factor governs temporal shifting and broadening, while the array factor reshapes the transverse energy flow and drives steady-state evolution. This work advances the fundamental research on spatiotemporally twisted array beams in strongly nonlocal nonlinear media.
The inherent dispersion of spoof surface plasmon polariton (SSPP) transmission lines-where group velocity decreases monotonically with frequency-constrains their deployment in applications demanding constant group delay....The inherent dispersion of spoof surface plasmon polariton (SSPP) transmission lines-where group velocity decreases monotonically with frequency-constrains their deployment in applications demanding constant group delay. Here, we propose a waveguide-integrated SSPP (WISSPP) structure that achieves broadband low-dispersion characteristics through intrinsic dispersion engineering. The unit exhibits a transition from anomalous to normal dispersion, yielding a U-shaped group delay profile with near-zero group delay dispersion at the design frequency. Experimental validation demonstrates group delay variations within 7% across the 8-12 GHz band. The proposed structure preserves the miniaturization advantages of SSPP circuits while enabling customizable center frequency and unit-length delay time through simple parameter adjustment, thereby expanding the application prospects of SSPP technology in integrated microwave systems.
Nonlinear amplification in large-core fibers is a potentially attractive approach to high-power short-pulse generation, but transverse mode coupling and the consequent beam degradation are concerns. Robust single-mode op...Nonlinear amplification in large-core fibers is a potentially attractive approach to high-power short-pulse generation, but transverse mode coupling and the consequent beam degradation are concerns. Robust single-mode operation of a multimode fiber amplifier can be achieved in a regenerative amplifier, but this has only been demonstrated in linear amplification. Here, we investigate single-mode nonlinear amplification in a multimode-fiber regenerative amplifier. Pronounced mode coupling is observed when the amplified pulse accumulates a large nonlinear phase; however, cavity-assisted mode selection can suppress mode coupling and improve the spatial beam quality. By optimizing the seed pulse duration, pulse energies up to 10 μJ with good beam quality are achieved and subsequently compressed to 98 fs duration. Factors that limit the performance of this amplifier are discussed.
This paper proposes a probabilistic shaping modulation scheme based on index-driven constellation partitioning. The 32QAM constellation is divided into eight non-overlapping energy-level patterns, with every three consec...This paper proposes a probabilistic shaping modulation scheme based on index-driven constellation partitioning. The 32QAM constellation is divided into eight non-overlapping energy-level patterns, with every three consecutive subcarriers grouped as a mapping unit controlled jointly by index bits through a predefined lookup table. By assigning more subcarriers to low-energy constellation modes located in the inner circle, the activation probability of low-energy symbols is increased, thereby reducing the average transmit power. Experimental validation is conducted over a 2 km seven-core fiber optic system. Experimental results demonstrate that at a bit error rate (BER) of 3.8 × 10, the proposed index-driven constellation-shaped signal achieves up to 0.53 dB gain compared to uniform 32QAM signals. Meanwhile, the BER performance variation among different modes remains below 0.5 dB. With low implementation complexity, the proposed scheme exhibits promising potential in multi-user optical access scenarios.
Microwave photonic (MWP) technology is widely used in signal generation and processing, which helps optical sensors achieve higher measurement resolution and sensitivity. In this Letter, MWP technology is used to improve...Microwave photonic (MWP) technology is widely used in signal generation and processing, which helps optical sensors achieve higher measurement resolution and sensitivity. In this Letter, MWP technology is used to improve the performance of distributed acoustic sensors based on an ultra-weak fiber Bragg grating array. Specifically, a linear-frequency-modulation (LFM) pulse is used as a probe signal, effectively improving the excitation threshold of fiber nonlinearity. Distributed positioning and quantitative measurement of vibration are achieved through a simple direct-detection scheme. Based on the non-matching interference, the echo beating frequency after chirp removal is reduced to an integral multiple of the LFM probe repetition rate, which helps to reduce the bandwidth of the receiving end. Compared with existing demodulation methods, the demodulation method combining phase shift integration and empirical mode decomposition reduces the noise floor by at least 7.6 dB.
We demonstrate topology-orientation separability in structured-light-driven magnetization in a tight-focusing regime. A nonzero vortex-charge mismatch produces an azimuthal phase beating that generates a twisted optical...We demonstrate topology-orientation separability in structured-light-driven magnetization in a tight-focusing regime. A nonzero vortex-charge mismatch produces an azimuthal phase beating that generates a twisted optical spin density through nonparaxial transverse-longitudinal coupling, thereby inducing three-dimensional magnetization textures via the inverse Faraday effect. Crucially, the tilt-angle pair (,) rotates the global magnetization orientation without altering the -defined twisted topology. These two orthogonal control channels, not achievable within a single-beam configuration, enable deterministic steering of three-dimensional magnetization textures and scalable twisted magnetization lattices. This minimal two-parameter framework provides a compact route toward multidimensional opto-magnetic control.
We report an integrated gain polarizer through femtosecond-laser direct inscribed 45°-tilted fiber grating (45°-TFG) in erbium-doped fiber (EDF), serving as a unique mode-locking element to generate stable ultrafast puls...We report an integrated gain polarizer through femtosecond-laser direct inscribed 45°-tilted fiber grating (45°-TFG) in erbium-doped fiber (EDF), serving as a unique mode-locking element to generate stable ultrafast pulses. Our monolithic device exhibits a polarization-dependent loss (PDL) exceeding 6dB within a range of 80nm while simultaneously serving as a gain medium. Subsequently, it was incorporated into a fiber laser and effectively initiated mode locking via the nonlinear polarization rotation mechanism. The laser produced a stable dispersion-managed soliton centered at 1563.5nm with a pulse duration of 127fs at a fundamental repetition rate of 80.8MHz. Numerical simulations corroborate the experimental results and further unveil the intracavity pulse evolution dynamics. These results contribute to the design of advanced ultrafast fiber lasers with a highly compact and robust configuration.
A half-open cavity random fiber laser with tunable feedback intensity by leveraging strong random feedback between erbium-doped fiber (EDF) gain and Rayleigh scattering-enhanced fiber (RSEF) has been constructed. The las...A half-open cavity random fiber laser with tunable feedback intensity by leveraging strong random feedback between erbium-doped fiber (EDF) gain and Rayleigh scattering-enhanced fiber (RSEF) has been constructed. The laser output characteristics of the established random laser have been measured with 20 m RSEF and 5-km SMF, respectively. Results show that RSEF could be beneficial to the enhancement of spectral purity, linewidth narrowing, and stabilization of output power. Furthermore, the influence of feedback intensity on the output laser properties has also been systematically investigated, with the optimal performance of single-frequency random laser output with an optical signal-to-noise ratio (OSNR) of 55.5 dB, relative intensity noise (RIN) of -100 dB/Hz, and a linewidth of 307 Hz.
Angle sensitivity to incident light remains a fundamental limitation in conventional Fabry-Pérot (F-P) and guided-mode resonance (GMR) filters due to the angular dependence of the transverse wave vector. In this work, we...Angle sensitivity to incident light remains a fundamental limitation in conventional Fabry-Pérot (F-P) and guided-mode resonance (GMR) filters due to the angular dependence of the transverse wave vector. In this work, we propose a compact planar notch filter based on localized guided-mode resonance (LGMR) by embedding a metallic grating within a tri-layer SiO-Si-SiO structure. The design achieves three-dimensional (3D) confinement of the transverse wave vector, effectively suppressing angular dispersion and stabilizing the resonance condition. Numerical simulations based on the finite-difference time-domain (FDTD) method demonstrate a flat stop band near 1.55 µm with a minimal wavelength shift of only 7.4 nm over a broad angular range of 0°-70°. Spectral tunability in the near-infrared (NIR) region is realized through controlled adjustment of the grating period. The proposed LGMR notch filter provides a robust and integrable solution for angle-insensitive spectral filtering in applications such as Raman spectroscopy and optical communication.
Quantum key distribution (QKD) theoretically offers information-theoretic security. The prevailing approach is the prepare-and-measure BB84 protocol, which implements QKD using a conventional laser rather than a single-p...Quantum key distribution (QKD) theoretically offers information-theoretic security. The prevailing approach is the prepare-and-measure BB84 protocol, which implements QKD using a conventional laser rather than a single-photon source via the decoy-state method. However, side-channel attacks targeting sources severely threaten system security. Despite extensive efforts, including a fully passive scheme, this vulnerability persists even with a perfect single-photon source. Here, we propose a source-independent (SI) QKD protocol that resolves all known and unknown source-side attacks without pre-sending an entanglement source. Aligning with advances in quantum light sources, our protocol simultaneously doubles the transmission distance while remaining robust against imperfection of source. Theoretical analysis shows that non-classical light source provides practical security advantages unattainable with a conventional laser.
In this paper, we propose a compact 180° adiabatic tapered waveguide bend based on a higher-order Bézier curve. By co-optimizing the inner and outer boundaries of the Bézier profile, the design achieves simultaneous high...In this paper, we propose a compact 180° adiabatic tapered waveguide bend based on a higher-order Bézier curve. By co-optimizing the inner and outer boundaries of the Bézier profile, the design achieves simultaneous high-efficiency adiabatic transmission and 180° optical path reversal between narrow and broadened waveguides. Fabricated on a 400 nm silicon nitride platform, the proposed bend features a small bending radius of 20 μm, achieves a waveguide width variation from 0.8 μm to 2.5 μm, and exhibits an insertion loss below 0.01 dB across the 1290-1330 nm wavelength range. This compact, broadband, and fabrication-tolerant 180° bend provides a vital building block for high-density, low-loss photonic integrated systems.
We report on the experimental generation of polarization symmetry-broken cavity solitons (SB-CSs) in a passive, fiber-based, coherently driven, Fabry-Pérot (FP) Kerr resonator. Polarization-resolved measurements reveal t...We report on the experimental generation of polarization symmetry-broken cavity solitons (SB-CSs) in a passive, fiber-based, coherently driven, Fabry-Pérot (FP) Kerr resonator. Polarization-resolved measurements reveal the spontaneous transition of initially symmetric CSs into asymmetrical vectorial states, triggered by a cross-phase modulation-induced polarization bifurcation. Most notably, due to counter-propagation of light occurring in FP resonators, we unveil a collective polarization conformity effect, whereby multiple CSs circulating in the cavity converge to the same asymmetric polarization state once their number exceeds a certain threshold. These results demonstrate that Fabry-Pérot resonators support novel collective soliton dynamics that are absent in ring architectures.
Miao K, Gu T, Song X
… +20 more, Liu Y, Cao K, Cheng R, Kang H, Hou X, Fu S, Qian Z, Yao T, Ma J, Li Y, Zhou A, Zhou W, Wang H, Xu X, Li L, Wang Y, Li F, Jia B, Wang F, Shen D
Flat-top beams exhibit symmetrical intensity and steep edge in cross-section with wide application. Especially, orbital angular momentum (OAM) endows it with the potential to achieve uniform angular momentum transfer or...Flat-top beams exhibit symmetrical intensity and steep edge in cross-section with wide application. Especially, orbital angular momentum (OAM) endows it with the potential to achieve uniform angular momentum transfer or phase encoding. In this Letter, we observed a flat-top beam carrying + OAM by intracavity incoherent superposition in an X-cavity Tm: YAG ceramic laser. The corresponding factors are 2.24 and 2.08 with a typical output power of 470 mW around ~2011.2 nm. Simultaneously, a radially polarized vortex beam (RPVB) with + OAM was observed. Further simulations and experiments revealed that a flat-top beam is formed by the incoherent superposition of RPVB and a Gaussian beam. Using a homemade M-Z interferometer, we observed vortex stripes' chirality reversal before and after the focal plane of the convex lens. To the best of our knowledge, this is the first observation of a flat-top beam with OAM at 2 µm wavelength.
Optical analog computing has garnered significant attention due to its potential in real-time, high-throughput image processing. However, existing image processing approaches are constrained by the trade-off between nume...Optical analog computing has garnered significant attention due to its potential in real-time, high-throughput image processing. However, existing image processing approaches are constrained by the trade-off between numerical aperture and transmission efficiency. To address this, we propose a transmissive metasurface capable of performing isotropic second-order spatial differentiation with a high numerical aperture (NA = 0.34) and over 53% peak cross-polarization conversion efficiency. By exploiting the detuned quasi-BIC and generalized Kerker effect, we intentionally introduce a spectral offset between electric and magnetic dipole resonances. This strategy smooths the phase dispersion in momentum space, ensuring resonant modes are suppressed at normal incidence (maintaining a dark background) while evolving to satisfy the first Kerker condition (|ED| ≈ |MD|) strictly at oblique incidence. Our work effectively overcomes the trade-off between numerical aperture and efficiency, laying the foundation for compact, high-performance edge detection systems in the microwave and millimeter-wave bands.
This study successfully generated dual-wavelength cylindrical vector beams at 1.06 μm and 1.34 μm in an Nd:GdVO laser. By employing resonator design and exploiting the birefringent properties of the laser crystal, both b...This study successfully generated dual-wavelength cylindrical vector beams at 1.06 μm and 1.34 μm in an Nd:GdVO laser. By employing resonator design and exploiting the birefringent properties of the laser crystal, both beams exhibited collinearity and high beam quality. Moreover, by simply adjusting one of the output couplers, the dual-wavelength beams could be tuned to achieve either identical polarization or orthogonal polarization without requiring any additional optical components. This dual-wavelength and polarization-tunable laser is expected to have significant application value.
Germanium-on-silicon (Ge-on-Si) photodetectors (PDs) have been widely used in silicon photonics. However, their saturation power is often relatively low. Here, a compact and high-power lateral PIN Ge-on-Si PD featuring a...Germanium-on-silicon (Ge-on-Si) photodetectors (PDs) have been widely used in silicon photonics. However, their saturation power is often relatively low. Here, a compact and high-power lateral PIN Ge-on-Si PD featuring a novel, to the best of our knowledge, butt-side-hybrid coupling structure is proposed and demonstrated by simulation. The input light is split into 3 paths, where the center one is directly butt coupled to the Ge-on-Si waveguide and the other two facilitate the gradual side coupling through higher-order-mode excitation. By engineering the field distribution and mode conversion process, the optical power can be more uniformly distributed across the Ge region, to significantly mitigate the saturation effect. Simulation results show a saturation power of 23 mW under -3 V bias and a maximum current density of 5.60 mA/μm. With a compact footprint of 7 μm × 30 μm, it is suitable for high-density silicon photonic integration.
We experimentally and numerically reveal a spatio-spectral coupling (SSC) mechanism mediated by spatially dependent gain in the spatio-temporally mode-locked fiber laser. In the experiment, the spectral tuning is observe...We experimentally and numerically reveal a spatio-spectral coupling (SSC) mechanism mediated by spatially dependent gain in the spatio-temporally mode-locked fiber laser. In the experiment, the spectral tuning is observed to be accompanied by a change in the spatial mode content. To further elucidate this relation between the spectral and spatial properties of the three-dimensional (3D) pulse, the gain spectrum and its field attractor are theoretically analyzed. The underlying mechanism through which the multimode gain affects the SSC is identified with the simulated results that well reproduce the modal composition exponentially varying with the spectral centroid. Moreover, harnessing the SSC enables the generation of asynchronous dichromatic 3D pulses, offering a potential route for dual-comb generation in a single laser cavity.
We demonstrate a few-mode Yb-doped fiber Mamyshev oscillator that directly generates megawatt-level peak power femtosecond vector vortex beams. Mode selection is achieved via engineered mode- and polarization-dependent i...We demonstrate a few-mode Yb-doped fiber Mamyshev oscillator that directly generates megawatt-level peak power femtosecond vector vortex beams. Mode selection is achieved via engineered mode- and polarization-dependent intracavity losses, enabling stable operation in the targeted spatial mode. The oscillator delivers radially and azimuthally polarized pulses with ~4.86 W average power and ~260 nJ pulse energy, externally compressed to 65 fs, corresponding to a ~2.9 MW peak power. First-order optical vortex pulses are also obtained with comparable energy and duration. These results represent, to our knowledge, the shortest pulses and highest peak powers reported for vector vortex beams generated directly from a fiber oscillator, advancing ultrafast structured-light sources for high-field and materials-processing applications.
We propose a protocol for efficient synthesis of vector-twisted beams with higher-order Poincaré polarization states via the random vector-mode decomposition method, where the polarization state and twist phase informati...We propose a protocol for efficient synthesis of vector-twisted beams with higher-order Poincaré polarization states via the random vector-mode decomposition method, where the polarization state and twist phase information are encoded into the deterministic and random complex amplitude parts of vector modes, respectively. Further, a compact vector-twisted beam generation system involving a phase-only spatial light modulator and a common-path interferometer is established. Multiple types of vector-twisted beams are successfully synthesized, and their propagation properties, including intensity, polarization state, and degree of polarization, are investigated in detail. Our results reveal that the twist phase can induce the local spin angular momentum splitting or redistribution and resist the coherence-induced depolarization during beam propagation, offering what we believe to be a new degree of freedom to modulate polarization in random vector beams.