DAC-less optical transmitters offer a critical low-power solution for high-speed fronthaul but face severe linearity and chirp constraints on silicon platforms. In this work, we demonstrate a high-performance O-band dual-drive Mach-Zehnder modulator (MZM) based on the thin-film lithium niobate (TFLN) platform. The device exhibits a 3 dB electro-optic bandwidth of 70 GHz. By independently driving the dual arms with binary electrical signals, we realize DAC-less PAM-4 generation at 140 Gbps per lane, with an extinction ratio of 4.92 dB. This demonstration confirms the potential of DUV-processed TFLN modulators as a key enabling technology for energy-efficient, high-speed, and low-latency 6G fronthaul applications.

Active control of multi-mode light–matter interactions is crucial for advancing quantum photonic technologies. Although triple-mode plasmon–exciton systems involving two distinct excitonic transitions offer a pathway to multi-level polaritonic states, achieving reversible electrical tuning at room temperature remains challenging. Here, we numerically investigate an electrically tunable triple-mode strong-coupling system comprising a J-aggregate-coated Au@Ag nanorod coupled with monolayer WS2. The simulated spectra show a UPB–LPB energy separation of approximately 239 meV near the zero-detuning condition. A modest gate voltage (2.0 V to 3.8 V) selectively modulates the middle and lower polariton branches over ∼46 meV, while the upper branch remains largely unaffected. This selective control is elucidated via a triple-mode coupled-oscillator model and Hopfield coefficient analysis, linking the polariton response to the excitonic composition. These results establish a framework for electrically reconfigurable multi-level polaritonic devices, offering potential for ultracompact optical modulators, high-sensitivity multiplexed sensors, and programmable quantum photonic circuits.

Temporal soliton formation requires a precise balance between dispersion and nonlinearity, yet this balance is easily disrupted, driving pulses into broadened, breathing, or breakup states. In this work we propose a universal strategy for temporal soliton generation and stabilization based on a phase framework that simultaneously accounts for dispersion, second-order (2nd-NL) and third-order (3rd-NL) nonlinearities. In this framework, pump-parameter phase diagrams map regions of nonsolitonic distortion, breathing-type dynamics, and stable soliton propagation. By engineering competing or synergic interactions between 2nd-NL and 3rd-NL, operating pump conditions can be steered from distorted or breathing regimes into the stable-soliton domain. Using intentionally detuned phase-matched conditions, second-harmonic generation induces a controllable temporal chirp that either compensates or reinforces 3rd-NL effects, substantially expanding the soliton stability window by achieving robust balance with dispersion. Simulations show that such optimized periodically poled lithium niobate structures enable tunable competing or synergic nonlinearities supporting soliton propagation over pump-parameter space with a wavelength range of 1.1-5 & micro;m and intensities of 3.5-175 GW/cm2, even with second-harmonic generation efficiencies below 1%, substantially extending the accessible regime for broadband, phase-coherent, ultrafast soliton control far beyond single-nonlinearity limits.

Nanophotonic supercontinuum generation offers a practical route to chip-based f-2f interferometry by leveraging coexisting chi(2) and chi(3) nonlinearities. In conventional uniform waveguides, the phase-matching bandwidth for second-harmonic generation (SHG) is intrinsically narrow, restricting the spectral overlap factor for heterodyne beating. To address this limitation, we introduce a periodically-tapered nanophotonic waveguide made from MgO-doped, z-cut thin-film lithium niobate for energy-efficient and fabrication-robust f-2f operation. By adiabatically varying the waveguide width within a dual phase-matching window that supports concurrent dispersive wave (DW) emission and SHG, we routinely achieved a broad spectral overlap between the SHG and DW components. This capability enables robust detection of the carrier-envelope offset frequency (fceo) at substantially lower pulse energies than that in uniform-waveguide approaches. We further developed a compact waveguide module that operates reliably under temperature fluctuations and is capable of interfacing with high-repetition-rate (500 MHz) mode-locked lasers, enabling detection and phase locking of fceo with a signal-to-noise ratio of 48 dB. These results highlight the potential of nanophotonic chips for developing compact, field-deployable frequency comb systems.

Light carrying orbital angular momentum (OAM) has emerged as a promising tool for manipulating light-matter interactions, providing an additional degree of freedom to explore chiral-optical phenomena at the nanoscale. When such vortex beams interact with chiral metamaterials, a unique phenomenon of optical asymmetry known as vortical dichroism (VD) arises. Nevertheless, most existing chiral metamaterials exhibit limited VD responses, and the underlying physical mechanisms are yet to be fully clarified. In this work, we propose three-dimensional spiral metamaterials that achieve gigantic VD effect. This pronounced VD effect originates from the intrinsic coupling between the spiral structure and the chirality inherent to optical vortices, which leads to strongly asymmetric scattering intensities for left- and right-handed OAM beams of opposite topological charges. Numerical simulations confirm a remarkable VD value of 0.69. Further analysis of electric field distributions reveals that the asymmetric VD response stems from a handedness-dependent excitation of distinct electromagnetic modes. For opposite handedness, spatial mode mismatch results in enhanced scattering. In contrast, matching handedness enables efficient energy coupling into a guided spiral mode, which suppresses scattering. These findings not only deepen the physical understanding of VD mechanisms but also establish a versatile platform for developing advanced chiral photonic devices and enhancing OAM-based light-matter interactions.

Supercontinuum generation from ultrashort pulses represents a significant phenomenon in nonlinear optics, with extensive applications in optical communications, biomedical imaging, and high-precision spectroscopy. However, the supercontinuum generation process involves complex spatiotemporal coupled nonlinear effects, where conventional numerical simulation methods inadequately address the evolutionary characteristics in both temporal and spatial domains simultaneously. To address this limitation, we propose a spatiotemporal decoupled split-step Fourier method (STD-SSFM) for solving the nonlinear Schr & ouml;dinger equation governing the spatiotemporal evolution of optical fields. This method distinctively separates temporal, spatial, and nonlinear terms within each propagation step and preserves complete spatiotemporal coupling dynamics through multi-step accumulation, thereby significantly simplifying computational procedures while maintaining the physical accuracy of spatiotemporal simulations. We have conducted numerical simulations of Ti:Sapphire femtosecond pulse laser beam propagation in fused silica. The results verify that this method can accurately capture the key pulse propagation features, including spectral broadening, temporal reshaping, spatial self-focusing, and nonlinear phase modulation. Compared to conventional approaches, our method fully preserves spatiotemporal correlation distributions and phase information during optical field evolution, and provides an efficient and reliable tool for a deeper understanding of supercontinuum generation mechanisms. (c) 2026 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

Through-silicon via(TSV)technology,as a critical three-dimensional interconnection architecture for advanced integrated circuits,has become increasingly vital for the development of the semiconductor industry.While femtosecond laser processing offers unique advantages for TSV fabrication due to its"cold processing"characteristics and minimal thermal damage,the wavelength-dependent mechanisms governing processing efficiency and quality remain insufficiently understood.This systematic study combines two-temperature model(TTM)simulations and experimental investigations to elucidate the physical processes and wavelength-dependent characteristics of femtosecond laser-induced breakdown in 300 μm-thick single-crystal silicon wafers at three representative wavelengths:800 nm,400 nm,and 266 nm. The TTM coupled with dynamic optical response analysis reveals that shorter wavelength lasers achieve superior breakdown efficiency through three synergistic mechanisms:1)enhanced initial carrier generation via higher single-photon absorption coefficients,2)accelerated electron heating rates,and 3)strengthened electron-lattice coupling efficiency proportional to carrier density.Using a real-time backward optical detection technique with a temporal resolution of 20 μs,we systematically measured the breakdown time as a function of laser fluence.The experimental results demonstrate a power-law relationship t ∝ F-nλ,where the exponent n exhibits pronounced wavelength dependence:n ≈ 2.70 for 800 nm,1.53 for 400 nm,and 1.12 for 266 nm.This monotonic decrease in n reflects the transition from multiphoton absorption-dominated to single-photon absorption-dominated carrier generation mechanisms.The minimum single-pulse energy required for breakdown decreases dramatically from approximately 150 μJ(corresponding to 0.39 J/cm2)at 800 nm to 30 μJ(0.32 J/cm2)at 266 nm,directly validating the theoretical predictions. Comprehensive morphological characterization combining optical microscopy and computed tomography(CT)three-dimensional reconstruction quantitatively reveals the wavelength-dependent hole features.At equivalent fluence,shorter wavelength lasers produce smaller hole diameters,but their normalized hole diameters(relative to focal spot size)significantly exceeding those of longer wavelengths at low-to-moderate fluences,indicating superior material removal efficiency.Notably,the heat-affected zone(HAZ)width for 266 nm laser remains essentially constant across the investigated fluence range,whereas the HAZ width for 800 nm and 400 nm lasers increase monotonically,demonstrating the superior thermal damage control offered by shorter wavelengths.This difference arises from the competition between material removal rate and the heat diffusion rate:shorter wavelengths achieve rapid material ablation on a picosecond timescale,before significant heat diffusion occurs on a nanosecond timescale.CT depth profiling further reveals that aspect ratios under low-to-moderate fluence conditions follow the order:266 nm＞400 nm＞800 nm,with shorter wavelengths producing steeper sidewalls favorable for subsequent metallization processes.However,at high fluences(＞1.0 J/cm2),shorter wavelength lasers exhibit breakdown time saturation due to plasma shielding effects.In contrast,800 nm lasers maintain higher breakdown rates across a broader energy window,attributed to their larger energy deposition depth and capability for higher total energy input. These findings establish clear wavelength-dependent processing regimes:shorter wavelength lasers(266 nm,400 nm)are optimal for high-precision fabrication of high-density,small-diameter TSVs(＜10 μm)in advanced packaging applications requiring stringent sidewall quality and minimal thermal damage.In contrast,longer wavelength lasers(800 nm)are more suitable for high-throughput processing of large-diameter TSVs(＞20 μm)or thick silicon wafers(＞500 μm),where processing speed is prioritized.This work provides comprehensive quantitative guidelines for wavelength selection and parameter optimization in femtosecond laser TSV fabrication,bridging fundamental ultrafast laser-matter interaction physics with practical semiconductor manufacturing requirements.

Polarimetry plays important roles in fields such as optical sensing, imaging, and communication. Current polarization detection schemes based on metasurfaces provide a feasible way for developing compact polarimeters. However, existing approaches face challenges that include insufficient accuracy, limited bandwidth, and complex operation/analysis procedures. Here, we propose a generic polarimetric scheme based on metasurface vector holography, capable of highly accurate, broadband, robust, and single-shot full-Stokes detection of arbitrary polarizations. This method encodes the polarization information (amplitude and phase of pairs of left- and right-hand circularly polarized light) of normally incident light into the intensity distribution of vector holographic images and then deciphers the polarization and intensity of light from the images by a trained neural network model. We show that the proposed scheme can achieve accurate polarization detection covering the entire Poincaré sphere in a broad wavelength range of 630-1200 nm. The average reconstruction errors of azimuthal and ellipticity angle at a wavelength of 635 nm can reach 0.58272° and 0.6715°, respectively, which is comparable to that of commercial polarimeters. Furthermore, due to the nature of holographic encoding and neural network decoding strategy, the method is immune to metasurface fabrication errors. Our design features high detection accuracy, wide operating wavelength range, robustness to fabrication errors, and direct readout from a single measurement. This study provides an efficient scheme for compact full-Stokes polarimetry and shows potential applications in fields including miniaturized optical systems, real-time sensing, and polarization imaging.

Valley photonics supports edge transport robust to sharp bends and disorder. However, conventional valley states, typically developed within a quantized valley Chern number framework, remain limited group velocity and bandwidth, restricting their applicability in high-speed, high-capacity on-chip transport. By relaxing the use of a sizable valley Chern number as the primary constraint in performance optimization, we leverage Dirac-mass engineering and electromagnetic mode control to simultaneously enhance the bandwidth and group velocity of valley transport. By combining extreme inversion-symmetry breaking with effective suppression of mode mixing, the platform restores an approximately scale-invariant interfacial mass profile, enabling both a maximized valley bandgap and a near-Dirac group velocity. Near-field measurements directly confirm unidirectional valley propagation with deep-subwavelength confinement and robustness against sharp bends. The system supports estimated error-free transmission at 2 Gbps and an open eye at symbol rates approaching the carrier frequency, with a carrier-normalized symbol rate exceeding those of previously reported valley photonic platforms by more than one order of magnitude. These findings establish a practical design route for high-performance valley photonics, offering ultrabroadband, high-velocity, and compact signal transport with potential applications in high-capacity photonic interconnect. The authors demonstrate ultrabroadband valley transport with near-Dirac group velocity through Dirac-mass engineering and mode control.

Optical fiber surface plasmon resonance (SPR) sensing, as a label-free, highly sensitive, rapid-response and in situ detection technology, has demonstrated significant utility in various physical, chemical and biological detection applications. This paper focuses on a fiber-integrated microscale spiral-grating tapered gold tip SPR sensor. We first introduce the working principle and sensing capability with high space–time resolution of this SPR microsensor. Then we provide a comprehensive description of its application in the study on the important fundamental scientific issue of liquid–liquid diffusion. Finally, we demonstrate the application of the spiral-grating tapered gold tip to plasmonic enhanced fluorescence and scanning near-field optical microscopy. By systematically summarizing the excellent multifunctional sensing performance of the microscale spiral-grating tapered gold tip, this paper aims to provide new optical schemes and tools for the study on complex physicochemical processes and light-matter interactions at microscale and nanoscale.

To address the demand for efficient optical coupling in back-illuminated mid-infrared focal plane arrays(FPAs),this paper numerically investigates a double-concave silicon-based air-microlens operating in the 3-5 μm wavelength range.Unlike conventional convex lenses,the proposed design embeds a concave air cavity within a high-refractive-index silicon medium,leveraging the strong refractive index contrast(△n≈2.42)to achieve tight beam focusing.Using the finite-difference time-domain(FDTD)method,we analyze the influence of the front curvature radius,rear curvature radius,and air cavity thickness on key focusing metrics.Physical mechanism analysis reveals that the double-concave architecture decouples the wavefront phase modulation process.Specifically,the front surface dominates the preliminary focusing,while the rear surface acts as a near-field phase corrector to suppress spherical aberrations and optimize the wavevector matching of high-frequency evanescent waves.For an illumination wavelength of 4 μm,the minimum focal spot size can reach 0.83 μm(approximately 71％of the effective wavelength λeff within the silicon medium).Based on these findings,we extract two typical design criteria to accommodate practical engineering trade-offs:a"minimum focal spot priority"design tailored for high-resolution arrays,and a"maximum depth of focus priority"design for systems requiring high thermo-mechanical assembly tolerances.The proposed"in-silicon focusing"architecture naturally fits the physical configuration of miniaturized infrared detectors,demonstrating significant potential for enhancing the fill factor of on-chip optoelectronic systems.

Supercontinuum generation (SCG) on thin-film lithium niobate platforms has opened new opportunities for applications in spectroscopy, metrology, and signal processing. However, the strong material dispersion of lithium niobate limits spectral broadening toward shorter wavelengths, particularly in waveguides without engineered domain structures, thereby restricting efficient SCG in the ultraviolet-to-visible region. Here we propose and theoretically demonstrate a new approach to overcome this limitation by harnessing higher-order waveguide modes. We show that femtosecond pumping near the visible spectrum can excite soliton fission and dispersive wave radiation in higher-order modes, efficiently transferring pump energy toward shorter wavelengths. Numerical simulations reveal that, under appropriate waveguide design and femtosecond pumping at a center wavelength of 860 nm, the excitation of the TE10 mode enables broadband SCG spanning 430-1260 nm at a-30 dB level. Our findings offer a simple and effective strategy for chip-scale SCG in the visible regime and pave the way for compact short-wavelength coherent frequency comb sources.

The coexistence of antichiral one-way edge states (AOWESs) and one-way bulk states (OWBSs) has recently been investigated in honeycomb photonic crystals, yet their realization in square photonic crystals, which is crucial for achieving a complete understanding and broader applicability of such topological phenomena, has not been reported. In this work, we propose a two-dimensional (2D) square photonic reduced Haldane model by applying opposing magnetic fields to yttrium iron garnet cylinders in adjacent rows to effectively analogize the horizontal hoppings in electronic systems. This model simultaneously supports both AOWESs and OWBSs. Remarkably, in both the theoretical analysis and experimental realizations of 2D air-loaded square gyromagnetic photonic crystals based on this model, we demonstrate that counter-propagating AOWESs above the light cone can be suppressed through appropriate scattering boundary conditions, resulting in a system that exclusively hosts pure OWBSs. These bulk states are further shown to enable robust, large-area one-way transport of electromagnetic waves. Our findings not only expand the understanding of topological states in square fermionic and bosonic systems, but also open new avenues for the development of robust, large-area energy transmission devices featuring unidirectional conduction.

Target-oriented discovery under limited evaluation budgets requires making reliable progress in high-dimensional, heterogeneous design spaces where each new measurement is costly, whether experimental or high-fidelity simulation. We present an information-theoretic framework for target-oriented adaptive sampling that reframes optimization as trajectory discovery: instead of approximating the full response surface, the method maintains and refines a low-entropy information state that concentrates search on target-relevant directions. The approach couples data, model beliefs, and physics/structure priors through dimension-aware information budgeting, adaptive bootstrapped distillation over a heterogeneous surrogate reservoir, and structure-aware candidate manifold analysis with Kalman-inspired multi-model fusion to balance consensus-driven exploitation and disagreement-driven exploration. Evaluated under a single unified protocol without dataset-specific tuning, the framework improves sample efficiency and reliability across 14 single- and multi-objective materials design tasks spanning candidate pools from 600 to 4 × 10^6 and feature dimensions from 10 to 10^3, typically reaching top-performing regions within 100 evaluations. Complementary 20-dimensional synthetic benchmarks (Ackley, Rastrigin, Schwefel) further demonstrate robustness to rugged and multimodal landscapes.

An intense ultrafast pulse white laser with continuous and ultraflat spectral coverage from deep-ultraviolet (DUV) to far-infrared (FIR) can open up a new arena of full-spectrum laser spectroscopy with applications to a wide variety of basic science and technology areas. Here, we present the creation of an intense white laser with 200-25,000 nm bandwidth @17 dB and similar to 1 mJ pulse energy by exploiting the synergic action of a high-efficiency nonlinear up-conversion module and down-conversion module upon an intense mid-infrared (MIR) seed pulse laser. The MIR seed pulse laser of 3.62 mJ pulse energy is achieved by sending an optical-parametric chirped pulse amplification pulse laser of 7.12 mJ pulse energy and 3.9 mu m central wavelength through a krypton gas-filled hollow-core fiber. The up-conversion nonlinear module is a deliberately designed chirped-periodic poling lithium niobate (CPPLN) nonlinear crystal supporting simultaneous broadband second-order nonlinear 2nd-12th harmonic generation upon the seed laser to generate the shortest DUV wavelength down to 200 nm with a nearly 40% conversion efficiency. The down-conversion nonlinear module is composed of a bare LN crystal offering third-order nonlinear spectral broadening effect and a cascaded AgGaSe2 nonlinear crystal offering high-efficiency intra-pulse difference-frequency generation, and generates a 2000-25,000 nm MIR-FIR laser with an overall conversion efficiency of 18%. The intense 7-octave ultraflat DUV-FIR white laser would offer an unprecedented power to simultaneously probe and monitor the electronic transition, molecular vibration, and lattice oscillation in a wide variety of physical, chemical, and biological substances and processes.

Metasurfaces enable exceptional optical wavefront manipulation at the subwavelength scale, underpinning diverse applications from structural-color nanoprinting to meta-holography. Although recent advances have integrated these dual functionalities within a single device, such platforms remain intrinsically static, constraining their practical utility. Here, we introduce a dynamically reconfigurable metasurface platform based on the phase-change material Ge2Sb2Se4Te1 (GSST), overcoming this fundamental limitation. By exploiting the orthogonal transmission properties of GSST meta-atoms and employing a phase-dependent spatial multiplexing strategy, we achieve precise control over the near-field electric field intensity distribution, enabling active switching of nanoprinting images. Simultaneously, the Pancharatnam-Berry phase is independently tailored within each pixel to manipulate the far-field wavefront for holographic projections, thereby realizing seamless integration of multi-state dynamic nanoprinting and multiplexed meta-holography. As a proof of concept, we numerically demonstrate two metasurface samples capable of triple-state, dual-mode dynamic switching, where both near-field patterns and far-field holograms are reconfigurable on demand. Furthermore, by incorporating the angular degeneracy associated with Malus' law, an additional near-field nanoprinting channel is established under orthogonal linear polarization paths, substantially enriching the functional dimensionality of the device. Building upon this platform, we further develop a high-security, multi-key, dual-level optical information encryption scheme that ensures robust physical-layer security against unauthorized access and information leakage. This work establishes a reliable and efficient pathway toward reconfigurable metasurfaces, unlocking opportunities for next-generation dynamic displays, advanced information encryption, optical anti-counterfeiting, and related applications.

Altermagnetism is a magnetic phase that combines zero net magnetization with time-reversal-symmetry breaking and momentum-dependent spin splitting, but it has so far been confined to fermionic systems. Here we report a photonic platform capturing the symmetry features of altermagnetism. Using a magnetophotonic crystal with staggered magnetic bias and controlled structural variation, we observe momentum-dependent polarization splitting, spin–momentum locking and vanishing net magnetization in the photonic band structure. By solving Maxwell’s equations, we show that the momentum-dependent splitting is symmetry governed, rather than a consequence of the momentum-independent gyrotropic effect. These results demonstrate a photonic analogue of altermagnetic behaviour and provide a route towards spin-functional photonic devices without net magnetization. Altermagnetism has been experimentally demonstrated in fermionic systems, but not yet in photonic systems. Now it is observed in a magnetophotonic crystal.

Chiral light-matter interaction in metasurfaces has drawn considerable interest for chiral sensing and spin-selective photonics. While quasi-bound states in the continuum(quasi-BIC) metasurfaces and transition metal dichalcogenides (TMDs) exciton-polariton systems have been widely explored, their circular dichroism typically deteriorates under oblique incidence, limiting practical applications that require wide-angle operation. In this study, we propose a symmetry-broken double-cross WS2 metasurface that maintains a stable chiroptical response over a broad angular range through two geometric parameters that can be optimized quasi-independently. The internal crossing angle α controls the quasi-BIC linewidth, while the inter-rod rotation angle β tunes the handedness-dependent coupling via the combined phase α + β. The resulting circular dichroism remains robust over ±0.1 rad, with a peak value of 0.96, while the quasi-BIC resonance simultaneously couples to the WS2 A-exciton to form exciton-polaritons with a Rabi splitting of 46 meV. Coupled-mode theory and multipole decomposition reveal that the chiral response originates from electric-magnetic dipole interference. These findings establish a quasi-independent tuning strategy for angle-robust chiral exciton-polaritons, paving the way toward wide-angle chiroptical devices.