Coherent Ising machines (CIMs) have emerged as a hybrid form of quantum computing devices designed to solve NP-complete problems, offering an exciting opportunity for discovering optimal solutions. Despite challenges such as susceptibility to noise-induced local minima, we achieved notable advantages in improving the computational accuracy and stability of CIMs. We conducted a successful experimental demonstration of CIM via femtosecond laser pumping that integrates optimization strategies across optical and structural dimensions, resulting in significant performance enhancements. The results are particularly promising. An average success rate of 55

Space-time singularities represent points where the local structure of a wave field becomes locally undefined, and are central to phenomena ranging from fluid dynamics to cosmology. In optics, spatiotemporal optical vortices (STOVs) provide a versatile setting in which to study such singularities, but their controlled manipulation during nonlinear frequency conversion has remained elusive. Here we show that the evolution of STOV singularities in second-harmonic generation can be continuously engineered through spatial Gouy-phase control. In a 4f system, translating a thin nonlinear crystal about the Fourier plane imposes a tunable Gouy phase that governs the orientation, splitting, and trajectories of singularities in the second-harmonic field. A Hermite-Gaussian modal description identifies Gouy-phase-dependent mechanism underlying these dynamics, in agreement with spatiotemporal interferometry measurements. Beyond integer-order inputs, fractional-order inputs (l=0.5) result in a distinct regime in which Gouy-phase bias drives topological reconfiguration and directional energy redistribution. Our results establish the Gouy phase as a simple yet powerful control knob for space-time singularities, opening new opportunities for structured-light engineering in nonlinear and ultrafast photonics.

Widely tunable femtosecond optical parametric oscillators (fs-OPOs) are attractive sources for ultrafast spectroscopy, nonlinear imaging, and nanophotonics, but their practical deployment is often limited by insufficient long-term stability. Here we present a high power, widely tunable femtosecond optical parametric oscillator with ultra-long-term stability over 12 h based on a model-free stochastic parallel gradient descent (SPGD) algorithm stabilization scheme. Pumped by the second harmonic of a Yb-fiber laser with a repetition rate of 49.22 MHz, the signal can be tuned from 660 to 1040 nm, with a maximum output power of 3.18 W at ∼ 800 nm. Unlike conventional feedback methods, the present approach enables stabilization both at the oscillation peak and at user-defined off-peak target-power operating points without either intentional modulation or complex adjustment of optical elements. RMS power fluctuations over 12 h of 0.31%, 0.99%, 0.29% are achieved at 770 nm, 800 nm, 830 nm, respectively. These results establish SPGD control as a practical route to robust long-term stabilization of widely tunable fs-OPOs for demanding applications in imaging, spectroscopy, and nonlinear photonics.

In this work, we demonstrate a widely tunable fiber-based optical parametric oscillator (FOPO) synchronously pumped by a high-power tunable picosecond Yb-fiber laser. The laser system features a compact and environmental-stable all-polarization-maintaining configuration. The wavelength tuning and cavity matching of the tunable Yb-doped mode-locked fiber laser (TYMFL) rely on an intracavity diffractive grating mounted on a motorized stage. By tuning the TYMFL from 1032 to 1078 nm, the FOPO outputs from 737 to 1014 nm, which is the widest wavelength coverage in near-infrared FOPOs, to the best of our knowledge. All wavelengths can be tuned continuously and reversibly. The demonstrated FOPO is naturally synchronized with the TYMFL, enabling its application as a low-cost, highly flexible laser source in high-resolution coherent Raman scattering imaging.

The characterization of timing jitter of mode-locked lasers with high resolution is crucial for generating optical pulses with minimal timing jitter. This is vital for high-precision applications including low-noise microwave generation, distance ranging, etc. We characterize the power spectrum density (PSD) of timing jitter of an Er-fiber mode-locked laser through extracting the phase of two beat notes between the mode-locked laser and two cavity-stabilized lasers (CSLs). The resolution of timing jitter measurement is approximately 10(-8) fs(2)=Hz, which is limited by the servo bumps from phase locking of the CSLs. The integrated timing jitter is 0.27 fs (10 kHz to 2 MHz). This paper leads the way in pioneering the utilization of CSLs for timing jitter characterization, a technique anticipated to be particularly advantageous for high-repetition-rate mode-locked lasers or frequency combs.

Precise timing jitter characterization is crucial for the advancement of ultrafast lasers and their applications. While the balanced optical cross-correlation method is routinely used, a self-heterodyne method with fiber delay provides a practical alternative without the need for a reference oscillator. Here, the timing detection noise floor of this method has been reduced to 8.49 zs/ /Hz, corresponding to a measurement resolution of 8.41 as within a 1 MHz bandwidth. The impact of environmental noise and fiber length on measurement sensitivity has been studied by characterizing a commercial low-noise femtosecond laser. This setup is particularly suitable for attosecond jitter measurements in timing synchronization and distribution applications.

Glass/Al/glass sandwich structures, which combine optical transparency, electrical insulation, and electrical conductivity, are attractive for applications in MEMS, optoelectronic sensors, and advanced packaging. However, reliable joining of glass and Al remains challenging because of their pronounced mismatch in physicochemical properties. In this work, a double-sided femtosecond laser welding strategy was proposed for the fabrication of glass/Al/glass sandwich joints. The effects of defocus, laser power, and repetition rate on plasma morphology, weld formation, and joint performance were investigated. An axisymmetric spatiotemporal extended nonlinear Schrödinger equation model coupled with a free-carrier rate equation was established to interpret defocus-dependent nonlinear propagation and energy redistribution in the glass. At 400 mW and 100 kHz, the line load reached 2.56 N/mm at a defocus of + 30 μm, corresponding to a stable filament-assisted welding regime, which was 15.3% higher than that obtained under the negative-defocus reference condition of −30 μm. The highest line load of 2.60 N/mm was obtained at 600 mW. The simulations showed that increasing positive defocus shifted the nonlinear interaction and axial energy-deposition regions toward the incident side. Excessive positive defocus caused premature energy depletion in the glass, whereas D = + 30 μm retained approximately 2.1 times more energy within the final 50 μm before the glass/Al interface than D = + 50 μm. Microstructural and chemical analyses revealed that joint formation was governed by localized interfacial melting, Al-rich material redistribution, micrometer-scale elemental transition, and oxygen-mediated interfacial reconstruction. This work establishes a processing and mechanistic framework for precision joining of multilayer glass/metal heterogeneous structures.

Objective With the rapid development of electronic technology, the requirements for wafer dicing techniques in chip packaging have become increasingly stringent. Traditional mechanical dicing tools are limited in depth control and unsuitable for wafers with complex surface structures such as waveguides. Although laser ablation techniques have been introduced to address these limitations, they often result in residue deposition and uncontrollable crack propagation, leading to chipping and damage at the wafer edge. This study addresses the cracking issue in the wafer dicing process caused by stress damage and proposes an optimized method based on stealth dicing technology. A dual-pulse-duration laser stealth dicing system is developed to enable efficient and precise cutting of both silicon-based and advanced compound wafers, such as sapphire and lithium niobate (LiNbO3). The system aims to minimize stress-induced damage while preserving the integrity of surface waveguide structures, thereby improving the reliability and lifespan of semiconductor devices. Methods A finite element method (FEM) combined with the J-integral approach is employed to simulate the stress field near cracks in multi-layered silicon wafers. The study focuses on the effects of crack depth and force application position on the crack opening displacement (COD) and stress distribution. A two-dimensional beam model is established to analyze the mechanical response of wafers during the dicing process and its influence on surface waveguide structures. In the experimental part, a dual-pulse-duration laser stealth dicing system is constructed, integrating a nanosecond Yb-doped fiber laser and a picosecond solid-state laser. The two laser beams are combined using a polarization beam splitter (PBS), and their scanning paths are controlled by a high-precision motion platform. Laser parameters and scanning strategies are optimized for different wafer materials, such as silicon-on-insulator (SOI), sapphire, quartz, and LiNbO3 , to validate the simulation results and evaluate the dicing quality. Results and Discussions The experimental results demonstrate that the proposed dual-pulse-duration laser stealth dicing system can achieve high-quality, damage-free dicing on various wafer materials. For silicon-based wafers, a stealth dicing depth of 120 mu m and an applied force at the center of the die are selected to minimize the surface stress response and preserve the integrity of waveguide structures (Figs. 9 and 10). Scanning electron microscope (SEM) confirms that the resulting waveguide end faces are smooth and flat, without the need for post-processing polishing (Figs. 12 and 13). For low-thermal-conductivity materials such as sapphire and quartz, picosecond laser stealth dicing is adopted to avoid thermal damage and maintain the quality of surface structures. A sapphire wafer with a 730 nm thick silicon nitride waveguide is successfully cut at a depth of approximately 70 mu m, achieving excellent structural preservation (Fig. 16). Similarly, a LiNbO3 wafer with a 600 nm thick LiNbO3 layer shows smooth and undamaged waveguide end faces after processing (Fig. 17). SEM images further confirms the absence of ablation residue, micro-chipping, or structural collapse, highlighting the system effectiveness in preserving micro/nano-scale features. Moreover, the system enables simultaneous dual-side stealth dicing of heterogeneously bonded wafers, eliminating the need for repeated alignment between different dicing systems and streamlining the overall dicing workflow, thus significantly improving production efficiency. Conclusions This study systematically reveals the influence of crack depth and force application position on the stress distribution during stealth dicing. The results show that when the crack depth exceeds 25 mu m, the crack opening displacement is stabilized and the surface stress is significantly reduced, providing a theoretical basis for damage-free dicing. The proposed dual-pulse-duration laser system is capable of adapting to both silicon-based and non-silicon-based materials, achieving high-precision and low-damage dicing. Compared with conventional mechanical and single-pulse-duration laser dicing technologies, the system proposed here exhibits superior performance in processing speed, chipping reduction, material compatibility, and structural integrity, particularly for wafers with waveguides, meta surfaces, and other complex structures. This research not only contributes to the advancement of domestic stealth dicing technology but also provides a feasible technical pathway for the future development of high-performance semiconductor and photonic devices with intricate designs.

In this work, an easily triggered dual-wavelength nonlinear polarization rotation (NPR) mode-locked fiber laser enabled by insertion loss control (ILC) is implemented. Dual-wavelength pulse operation is obtained by simply tuning intra-cavity loss. Without the need for the periodic filtering effect typically employed in dual-wavelength lasers, ILC also allows reproducible switching among various single-wavelength and dual-wavelength mode-locking states at its specific angle. Our work demonstrates a novel approach for reproducibly achieving dual-wavelength in spatial NPR mode-locked lasers. This flexible dual-wavelength laser source may be used for various high-precision applications, such as absolute ranging and molecular spectroscopy.

Broadband wavelength-tunable second-harmonic generation (SHG) is highly desirable for multifunctional photonic integration and nonlinear light sources. However, achieving efficient SHG with wide-range tunability in a compact device remains challenging. Here, we experimentally demonstrate a lithium-niobate-embedded photonic crystal (PhC) vertical cavity that concentrates optical defect-state resonances within the photonic bandgap and places them within the second-harmonic wavelength range. By exploiting multiple defect-mode resonances, which shift spectrally under oblique incidence and overlap with other resonances at normal incidence, the SHG enhancement peaks connect seamlessly across modes, enabling continuous resonance-assisted tuning over a pump wavelength span of about 350 nm. Our results offer a scalable approach toward broadband nonlinear wavelength conversion and integrated tunable light sources.

This paper reports a cascaded stimulated Raman soliton frequency-shift amplification (CSR-SFSA) scheme based on the combination of an erbium-ytterbium co-doped fiber (EYDF) and a phosphorus-doped fiber (PDF) for the generation of femtosecond soliton pulses in the 1.7-mu m spectral region. The EYDF functions as a narrowband pre-amplifier, preserving spectral coherence while suppressing incoherent components and reducing the effective Raman threshold in the subsequent PDF stage. The cascaded configuration enables a reduced Raman fiber length, mitigates walk-off effects induced by group-velocity mismatch, and supports stable single-soliton operation. With appropriate pump power and optimized fiber parameters, Raman-shifted solitons with center-wavelength tunability from 1.6 to 1.7 mu m are obtained, accompanied by a spectral tail extending toward 1.75 mu m. The system delivers an average output power of up to 150 mW and a maximum pulse energy of 2.17 nJ. At a pump power of 0.8 W, long-term measurements over two hours show a wavelength drift below 0.12 nm and a root-mean-square (RMS) power fluctuation of approximately 0.27%. The radio-frequency spectrum exhibits a signal-to-noise ratio (SNR) of 37 dB, indicating stable and low-noise soliton operation. The demonstrated CSR-SFSA scheme provides a compact and efficient approach for generating high-coherence ultrashort pulses in the 1.7-mu m spectral region, which is of interest for applications in biomedical imaging, nonlinear spectroscopy, and related photonic systems.

We present a fast method to produce height-controllable high-aspect-ratio (HAR) voxels in the two-photon polymerization process. By loading complex-amplitude encoded holograms onto a phase-only spatial light modulator (SLM), precise control over the axial intensity profile of a Bessel beam is achieved, enabling the fabrication of height-tunable HAR voxels in a single exposure without mechanical axial motion. The voxel height can be adjusted independently and continuously over a range of 15 μm while maintaining the constant lateral size of 1.3 μm simply by switching tailored Bessel beam holograms. As demonstrated, microneedle arrays and hollow circular and polygonal microtubes with graded heights were fabricated.

Vortex dynamics are intriguing and challenging across multiple physics fields. In optics, customized spatiotemporally structured optical fields, especially spatiotemporal optical vortices (STOV), offer the potential to tailor light via coupled space-time degrees of freedom. However, the interaction mechanisms between multiple transverse orbital angular momentum singularities within a single wave packet remain elusive. This study explores the intrinsic dynamics of a STOV with three phase singularities, observing a pronounced vortex singularity oscillation phenomena by tuning the temporal dispersion. We show that these phenomena originate from the counterintuitive spatiotemporal attractive effect between vortices, which is closely related to the singularity distance. Furthermore, the stretching into filaments and annihilation behaviors is observed by introducing antivortex in the center of the wavepacket. Experimentally, we propose a Full Interferometric Retrieval of Spatiotemporal Tomography (FIRST) method that enables the complete, single-shot capture of wave packets, with excellent agreement between theoretical predictions and experimental results. To the best of our knowledge, the dynamics of transverse spatiotemporal singularities within a single wave packet are reported here for the first time. These findings confirm the existence of interesting interactions between STOV singularities, deepen our understanding of photonics and open a new direction for investigating the complex dynamics of vortex singularities in the spatiotemporal domain.

We extended self-similar amplification to a large-mode-area tapered Yb-doped fiber (LMA T-YDF) with longitudinally decreasing nonlinearity. The theoretical analysis and numerical simulation demonstrate that T-YDFs with different nonlinearity profiles can achieve self-similar evolution, which is confirmed by a self-similar amplifier that employs two kinds of T-YDFs. Further experimental study indicates that the T-YDF with a large core diameter at the thin end can achieve self-similar evolution across a wide range of pump powers and generate 51 W average power, 34 fs nearly transform-limited (TL) pulses with 32 dB gain. To the best of our knowledge, this is the first theoretical and experimental demonstration of self-similar amplification in T-YDFs. The high-gain feature of the T-YDF simplifies the laser system and can be used to build a compact all-fiber high-power femtosecond laser source.

Femtosecond lasers enable high-quality engraving through cold ablation, but their low throughput constrains engraving efficiency. Moreover, for materials like stainless steel, excessive energy deposition during laser en graving induces periodic cone-like protrusions due to the material's intrinsic optical and thermal properties. This inherent trade-off between processing efficiency and quality presents a significant challenge. In this work, a femtosecond dual-pulse technique based on electron-lattice coupling modulation is employed to optimize the engraving process. By controlling the energy ratio and inter-pulse delay time between orthogonally polarized pulses, the convective flow driven by the surface temperature gradient is suppressed and the formation of mi crogrooves and melt columns at the bottom of the engraving pattern is prevented. Besides, a two-temperature model (TTM) is used to analyze temperature evolution between the electronic and lattice systems during the primary and secondary thermalization processes in modulation. Finally, appropriate parameters are selected and applied to the actual pattern engraving based on the removal depth and surface roughness measured by the con focal laser scanning microscope during the modulation. This approach can effectively reduce roughness by 2-3 times while maintaining comparable engraving efficiency. It demonstrates potential for efficiency optimization in precision laser engraving systems.

We demonstrate the generation of sub-5-ns pulses at 2 μm through an electro-optic (EO) cavity-dumped Tm:YAP laser using an x-cut hydrothermally grown potassium titanyl phosphate (KTP) electro-optic modulator. Compared with conventional flux-grown KTP, hydrothermal KTP exhibits superior intrinsic properties, including an ultrafast electro-optic switching response, high optical homogeneity, low electrical conductivity, and a high laser-induced damage threshold. By integrating symmetric dual-end pumping and intracavity thermal lens compensation, we enable the laser to achieve stable operation in the repetition rate range of 80–120 kHz. It is able to generate a narrow 4.7-ns pulse train, delivering the maximum average power of 6.47 W and a slope efficiency of 18.8 %. This high-performance 2 μm laser system shows significant potential for applications in atmospheric lidar and precision micromachining.

The 4H polytype of silicon carbide (4H-SiC) has excellent properties such as high electron mobility and high saturation electron velocity; it has therefore become an important material for high-power and high-frequency devices. In the slicing step of wafer fabrication, however, conventional wire-saw cutting is constrained by the inherent high hardness and brittleness of 4H-SiC, causing excessive material removal and surface and subsurface damage. To overcome these limitations, this study proposes a femtosecond laser slicing technology combined with side scribing. A simulation model of the boundary effect in internal laser processing was established to analyze the optical energy distribution under spherical aberration. The simulations revealed boundary regions that resist laser modification because of the coupling between asymmetric focusing and spherical aberration, which degrades the slicing quality of conventional laser processing. Systematic parametric experiments were then used to investigate the influence of the laser processing parameters on the formation of the modified layer. Targeted experiments performed using the optimized processing parameters provided a quantitative characterization of the hard-to-modify regions and guided the application of the side-scribing process. The peeling results demonstrate that the proposed side-scribing-assisted femtosecond laser slicing process effectively reduces the peeling stress and the cracking that occurs during slicing, achieving a 68% reduction in peeling stress and a 27% reduction in the arithmetic mean roughness Sa of the peeled surface, together with the formation of laser-induced periodic surface structures that are better suited to subsequent processing, compared with conventional laser slicing. This study improves the processability of 4H-SiC wafer slicing and provides a new approach to substrate preparation for wide-bandgap semiconductor materials.