Search Results (1,172)

Ultrafast fiber lasers operating near 2 μm have emerged as a critical platform for advancing mid-infrared photonics due to their narrow pulse durations, high peak powers, and broad tunability. These sources exploit the rich energy-level structures of Tm³⁺ and Ho³⁺ doped fibers and reside within an atmospheric transmission window, enabling applications spanning nonlinear microscopy, precision micromachining, optical frequency metrology, biophotonics, and free-space optical communication. Recent progress in low-loss fiber fabrication, dispersion-engineered cavity design, and mode-locking technologies has significantly expanded the performance boundaries of 2 μm ultrafast fiber lasers. This review systematically examines the underlying pulse-formation mechanisms and categorizes state-of-the-art mode-locking approaches. Representative laser architectures are compared with respect to pulse duration, energy scalability, repetition-rate enhancement, spectral characteristics, and environmental stability. Key application pathways in high-resolution spectroscopy, biomedical diagnostics, and mid-IR supercontinuum generation are highlighted. Finally, the remaining challenges and prospective research directions are discussed to inform the development of next-generation ultrafast photonic sources in the 2 μm band. Full article

In the fields of atomic physics, quantum sensing, and precision measurement, 852 nm lasers are essential for the resonant excitation and manipulation of the cesium (Cs) D₂ transition ($6S_{1/2}\to 6P_{3/2}$). While significant global progress has been made in developing 852 nm laser based on distributed feedback (DFB) lasers and external cavity diode lasers (ECDL), the burgeoning demand for portable and integrated quantum instruments imposes stringent requirements on miniaturization and long-term, maintenance-free operation. To address the challenge of mode competition in Faraday lasers, this work demonstrates a frequency-stabilized semiconductor laser based on an atomic frequency-selective architecture. By utilizing a customized Faraday Anomalous Dispersion Optical Filter (FADOF) for frequency selection, the laser wavelength automatically corresponds to the Cs 852 nm D₂ transition, offering “Plug-and-play” operation. To further enhance integration, we propose and demonstrate a miniaturized Faraday laser architecture that resolves the instability caused by the mismatch between the FADOF transmission bandwidth and the free spectral range (FSR) of the external cavity. By employing a 7000 Gs magnetic field, the FADOF bandwidth is actively broadened to ∼15 GHz, while the cavity length is concurrently compressed to 30 mm to maximize FSR to effectively suppressing unstable mode competition. The resulting laser achieves a highly compact dimension of $102\times 109\times 96{\mathrm{mm}}^3$. Performance testing demonstrates a Lorentzian fitted linewidth of $16.4\mathrm{kHz}$ and a 1-s frequency stability of $3.05\times {10}^{-13}$ after modulation transfer spectroscopy (MTS)-based frequency locking. This robust and autonomous 852 nm laser source provides a critical technological foundation for the miniaturization of high-performance quantum sensors. Full article

A micro-cavity based on phase-change material is a very important strategy for the realization of tunable absorption and conversion of terahertz waves. In this work, a tunable terahertz metamaterial absorber based on the phase-change material germanium–antimony–tellurium (GST) is demonstrated. The device features a metal–insulator–metal triple-layer structure, where the dynamic switching of absorption characteristics is achieved via thermally controlled GST phase transition. In the amorphous state, the absorber exhibits a single absorption peak at 7.7 THz. Upon crystallization, the absorption switches to dual peaks at 5.1 THz and 8.3 THz, achieving near-perfect absorption in both states. Full-wave electromagnetic simulations and theoretical analysis based on a multiple-reflection interference model indicate that this performance tuning originates from the GST-phase-transition-induced change in the equivalent optical cavity length. This corresponds to a switch between two resonant modes: coupled inner–outer ring resonance and independent outer ring resonance. These results provide a foundation for developing dynamically tunable terahertz devices with promising applications in terahertz communications, imaging, and sensing. Full article

Diode-pumped alkali vapor lasers (DPALs) offer high quantum efficiency, low thermal loading, excellent beam quality, and emission wavelengths matched to important application scenarios. Extending DPALs toward pulsed regimes is of particular interest for applications such as lidar, free-space optical communication, and precision material processing, where high peak power and flexible temporal control are required. This review surveys the key technologies underlying DPAL systems and summarizes the progress in pulsed-generation approaches. The pulsed techniques reported to date are systematically reviewed, including pump modulation, intracavity modulation, cavity dumping, and mode-locking, together with a comparison of their performance. The current status indicates that pulsed DPALs remain at an early stage, with limitations in parameter space exploration and performance scaling. Future developments are expected along several directions, including further exploration of mode-locked DPALs, burst-mode pulse generation for structured temporal output, power scaling through MOPA architectures, and spectral extension via nonlinear frequency conversion. These directions collectively define the pathway toward high-performance pulsed DPAL systems. Full article

Vertical-External-Cavity Surface-Emitting Lasers (VECSELs) have gained significant attention over the past two decades due to their versatility in a wide range of photonic applications. This review focuses on VECSEL configurations for dual-wavelength emission, highlighting their use in high-resolution spectroscopy, terahertz (THz) generation, and advanced optical communication. We explore recent developments in VECSEL designs, including systems utilizing birefringent crystals for polarization-based frequency separation and configurations with dual-VECSEL chips or dual-gain regions within a single cavity. These two-wavelength VECSELs enable diverse operation modes, including narrow-linewidth, pulsed, multimode, and frequency-converted emission, with high-brightness output, excellent beam quality, and tunable wavelengths. Additionally, the review discusses advancements in dual-frequency VECSELs, with applications in LIDAR systems for environmental monitoring, highly stable optical clocks, and fiber sensors. We examine improvements in cavity design, semiconductor structures, and power stabilization, which have enhanced frequency stability and spectral purity, making VECSELs suitable for precision metrology and sensing applications. Full article

This study evaluated the effects of four cavity disinfection protocols on microtensile bond strength (µTBS) and failure mode of dentin bonded with a universal adhesive in self-etch mode. Sixty human third molars were assigned to five groups (n = 12): Control (Clearfil S3 Bond Universal), Clearfil SE Protect Bond (CPB, MDPB-containing), 2% chlorhexidine (CHX), 5.25% sodium hypochlorite (NaOCl), and 200 ppm hypochlorous acid (HOCl). After disinfectant application and bonding, composite build-ups were sectioned into beams (≈0.9 mm²) and tested as immediate (24 h) and thermocycled (10,000 cycles) subgroups. Data were analyzed using two-way ANOVA, Tukey HSD, and chi-square/Fisher’s exact tests (α = 0.05). At 24 h, NaOCl and CHX produced significantly lower µTBS than the control, HOCl, and CPB groups (p < 0.05). After thermocycling, Control, CPB, and NaOCl declined significantly, while CHX remained stable (p = 0.960) and HOCl showed non-significant reduction (p = 0.086). NaOCl yielded the highest adhesive failure rate and lowest bond strength. CHX reduced initial µTBS but maintained stability. HOCl and CPB produced values comparable to controls, though HOCl was more aging-susceptible. MDPB-containing adhesives may preserve bond durability while providing disinfection. Full article

Persistent post-endometrial ablation uterine bleeding indicates that no method of EA eliminates the entire endometrium, and post-EA hysteroscopy shows a distorted and scarred uterine cavity in the majority of patients. These observations raise concerns regarding presentation, assessment and stage of potential post-ablation endometrial cancer (PAEC), developing in residual endometrium pockets. To better understand these concerns, a literature search was conducted, from the introduction of EA in the 1980s through 2025, to capture reports of endometrial cancer (EC) associated with or following EA using multiple data bases, imputing search terms of EC following EA and possible combinations of first- and second-generation EA techniques associated with EC. Upon review of all publications, we identified 86 ECs associated with EA, described in 20 case reports (N = 20), four case series (N = 18), eleven cohort studies (N = 21), one registry (N = 27) and five reviews. Based on 12 relevant studies at a median follow-up of 8.5 years (range 1.9–25), 43 EC were identified in 39,795 women with a history of EA, with a summary incidence of 0.11% (range 0.0–1.59%). Although the studies and data are very heterogeneous, it appears that EA may afford a protective effect in reducing the risk of EC in the short term. The mechanistic effect is likely due to a quantitative reduction in the endometrium that can potentially become malignant, and/or due to the elimination of occult pre- or malignant endometrial elements which are vulnerable to EA. Moreover, based on 25 evaluable cases, the mode and time to presentation, the diagnostic work-up (including endometrial biopsy and hysteroscopy), and the stage of PAEC appear not to be altered by EA. Full article

Surface Acoustic Wave (SAW) technology, long central to analog signal processing and RF filtering, is undergoing a major renewal. Driven by advances that decouple SAWs from traditional piezoelectric materials and fixed-function devices, the field is gaining unprecedented control over acoustic, optical, and electronic interactions at the micro and nanoscale. This review synthesizes these developments across four fronts: new physical mechanisms for SAW manipulation, emerging material platforms, ranging from thin films to 2D systems, along with reconfigurable device architectures and circuits, and the expanding landscape of applications they enable. Optical methods are reshaping how SAWs are generated and controlled, bypassing the limits of conventional electromechanical coupling. Coherent optical excitation of high-Q SAW cavities via Brillouin-like optomechanical interactions now grants access to modes in non-piezoelectric substrates such as diamond and silicon, while on-chip SAW excitation in photonic waveguides through backward stimulated Brillouin scattering opens new integrated sensing routes. In parallel, magneto-acoustic experiments have revealed nonreciprocal SAW diffraction from resonant scattering in magnetoelastic gratings. On the device side, ZnO thin-film transistors integrated on LiNbO₃ exploit acoustoelectric coupling to realize voltage-tunable phase shifters; UHF Z-shaped delay lines achieve high sensitivity in a compact footprint; and parametric synthesis of wideband, multi-stage lattice filters targets 5G-class performance. Atomistic simulations show that SAW propagation in 2D MXene films can be engineered via surface terminations, while aerosol jet printing and SAW-assisted particle patterning provide agile, cleanroom-light fabrication of microfluidic and magnetic components. These advances enable applications ranging from hybrid quantum systems and quantum links to lab-on-a-chip particle control, SBS-based and UHF sensing, reconfigurable RF front-ends, and soft robotic actuators based on patterned magnetic composites. At the same time, optical techniques offer non-contact probes of dissipation, and MXenes and other emerging materials open new regimes of acoustic control. Conclusively, they are transforming SAW technology into a versatile, programmable platform for mediating complex interactions in next-generation electronic, photonic, and quantum systems. Full article

In the deep mining of metal mines, the stability of pillar–backfill composite materials (PBCMs) under cyclic loading is crucial for preventing dynamic disasters in goafs. Although previous studies have extensively investigated backfill materials under static loading, the damage evolution mechanism of PBCM under cyclic disturbance—particularly the coupled effects of pillar width and disturbance amplitude—remains insufficiently understood. To address this gap, this study explored the mechanical properties and damage evolution of PBCM under cyclic loading using an indoor testing system. Tests were conducted on composite specimens with varying pillar widths (6, 9, 12, 15 mm) and disturbance amplitudes (3, 4, 5 MPa), combined with acoustic emission (AE), digital image correlation (DIC), and scanning electron microscopy (SEM). Results show that wide-pillar specimens (≥12 mm) exhibit significantly improved bearing strength and deformation modulus, with increases of nearly 90% and over 40%, respectively, compared to narrow-pillar specimens. Notably, wide pillars maintain over 95% strength stability even under 5 MPa cyclic disturbances. Narrow pillars are prone to localized damage concentration with high-frequency AE signals and shear failure, while wide pillars exhibit uniform damage development. Failure morphology confirms that pillar size dictates failure mode: narrow pillars undergo sudden through failure, whereas wide pillars display progressive composite failure, with fewer damage-induced cavities and directional crack propagation along maximum shear stress. These findings provide a theoretical basis for stope structure optimization and dynamic disaster prevention in deep mines. Full article

The 795 nm wavelength corresponds to the D1 transition of rubidium atoms and is widely used in atomic optical pumping, atomic clocks, magnetometers, and precision spectroscopy. For compact free-space collimation, beam shaping, and efficient fiber coupling, edge-emitting semiconductor lasers with reduced fast-axis (vertical) divergence are highly desirable, yet low-divergence designs at 795 nm remain limited. Here, we propose and demonstrate low-divergence photonic-crystal epitaxy (LD–PC) for 795 nm edge-emitting lasers. By engineering a periodic n-side photonic-crystal stack to place the fundamental vertical mode near the photonic band edge, the vertical mode is expanded while maintaining effective modal discrimination. Narrow-ridge Fabry–Pérot lasers based on GaAsP/AlGaAs single-quantum-well epitaxy were fabricated and characterized. The optimized LD–PC device (3 μm ridge width, 1 mm cavity length) delivers 227 mW at 200 mA with a threshold current of 23 mA, a slope efficiency of 1.28 W/A, and a peak wall-plug efficiency of 55% under continuous-wave operation at 25 °C. The measured far-field divergences (FWHMs) are 7.16° and 18.83° in the lateral and vertical directions, respectively, corresponding to a reduction in the vertical divergence from >40° in the reference structure to <20° with LD–PC. These results validate photonic-crystal epitaxy as an effective route toward compact, high-performance, low-divergence 795 nm semiconductor laser sources for rubidium-based atomic systems. Full article

We present the simulation-guided design and experimental demonstration of high-speed 940 nm vertical-cavity surface-emitting lasers (VCSELs). Utilizing established device optimization principles, a simulation study was conducted focusing on the number of oxide layers and the aperture size, which predicted a maximum modulation bandwidth of over 35 GHz. To validate the simulation, a device with a 4-μm double-oxide aperture was fabricated and characterized. Additionally, a Zn-diffusion process was incorporated during fabrication to reduce p-DBR resistance and suppress higher-order transverse modes. The fabricated device achieved an experimental modulation bandwidth of 34 GHz and demonstrated successful 100 Gbit/s PAM-4 data transmission. The close agreement between the simulated and measured performance highlights the successful practical integration of these techniques for developing high-speed optical interconnects. Full article

The study aimed to evaluate the effect of chlorhexidine (CHX), chlorin p6-mediated photodynamic therapy (PDT), magnesium oxide nanoparticles (MgONPs), and Clp6-functionalized MgONPs on smear layer removal and shear bond strength of a two-step etch-and-rinse adhesive to caries-affected dentin. Seventy-five human permanent molars with occlusal carious lesions and ICDAS scores of four and five were included. Twenty-five samples were used to prepare dentin discs 2 mm in thickness. The remaining samples, along with 25 discs, were arbitrarily allocated into five disinfectant groups, with n = 15 per group (10 teeth and 5 discs). Group I: Control, Group II: 2% CHX, Group III: Clp6-mediated PDT, Group IV: MgONPs, and Group V: Clp6-functionalized MgONPs. SL removal assessment, nanoparticle characterization, and EDX were performed using SEM. Fifty CAD were etched, followed by fifth-generation adhesive application and composite build-up. SBS and failure modes were evaluated with a universal testing machine and stereomicroscope, respectively. Group 4 (MgONPs) specimens displayed the maximum cleaning of SL (1.11 ± 0.13) and the highest SBS (10.32 ± 0.18 MPa). However, minimum SL removal (2.87 ± 0.94) and bond strength (7.42 ± 0.25 MPa) were exhibited by Group 1 (No disinfectant) samples. MgONPs possess the potential to be used as a cavity disinfectant, as they efficiently remove SL from CAD and augment the bond integrity outcomes. Full article

Multimodal high-resolution ultrasound, including B-mode, Power Doppler, MicroVessel Doppler, spectral Doppler, and strain elastography, was used to assess concomitant dactylitis and hidradenitis suppurativa (HS) in a 46-year-old woman with severe hidradenitis suppurativa (IHS4 = 28), who was diagnosed 1.5 years ago and has been using adalimumab. Axillary ultrasound demonstrated abscess cavities and draining fistulous tracts with marked structural distortion, increased vascular signal on advanced Doppler modalities, and heterogeneous stiffness patterns on elastography, consistent with active deep inflammatory involvement. Simultaneously, evaluation of the third right finger revealed flexor tendon sheath thickening, soft-tissue edema, Doppler-positive inflammatory activity, and altered biomechanical properties compatible with dactylitis. High-resolution ultrasound has been increasingly recognized as a valuable tool for evaluating inflammatory and structural changes in cutaneous diseases, including HS. These multimodal findings illustrate how structural, vascular, and biomechanical ultrasound parameters may provide complementary information for characterizing inflammatory tissue remodeling in HS associated with dactylitis. As this report describes a single patient, these elastographic observations should be considered exploratory and hypothesis-generating rather than evidence of clinical validation. Full article

Dual-frequency lasers with narrow linewidth and high coherence serve as essential light sources for systems such as heterodyne detection, LiDAR, and precision interferometry. However, existing technologies cannot directly separate the two frequency components at MHz-scale differences, which remains a persistent bottleneck in this field. In this paper, we present a dual-frequency fiber laser based on a bidirectional dual-path ring cavity. The proposed laser supports flexible switching between single-frequency and dual-frequency operation while allowing straightforward physical separation of the two outputs via intrinsic beam routing. In single-frequency mode, the two beams exhibit Lorentzian linewidths of 1.1 kHz and 1.16 kHz, respectively. In dual-frequency operation, the laser produces a beat signal at 470 MHz with a 3-dB linewidth of 340.2 Hz and a signal-to-noise ratio (SNR) exceeding 70 dB. This dual-frequency fiber laser provides a novel and practical source for heterodyne detection and LiDAR-based measurement systems. Full article

In computer-aided design/computer-aided manufacturing (CAD/CAM) restorations for severely damaged teeth, the cavity floor or proximal margins may be elevated with composite resin to improve adhesion. This in vitro study investigated how different surface pretreatment methods affect the shear bond strength (SBS) of hybrid CAD/CAM materials to dentin or composite surfaces, simulating clinical situations of composite elevation. Hybrid CAD/CAM samples were bonded to dentin or composite substrates following different surface pretreatment protocols and cemented using a dual-cure adhesive resin cement. The samples were thermocycled and subjected to shear bond strength testing, and failure modes were analyzed. The SBS in the sandblasting (SB)+Dentin group and hydrofluoric acid (HF)+Dentin was significantly higher than that in the SB+Composite and HF+Composite groups (p < 0.05). Untreated+composite and untreated+dentin groups showed significantly lower SBS (p < 0.05). Failure mode analysis revealed a predominance of cohesive failures in the SB+Dentin group, while adhesive failures were more frequently observed in most of the other groups. SB-treated and HF-etched hybrid CAD/CAM materials showed more favorable bonding behavior to dentin than to composite, highlighting that bonding to the elevated composite layer may be less effective than bonding directly to prepared dentin. Full article