Achieving broadband second-order nonlinear processes in a fully integrated fiber platform has long been a challenge, as silica fibers intrinsically lack second-order nonlinear susceptibility due to their centrosymmetric and amorphous structure. Here, we introduce an all-fiber strategy that overcomes this limitation by integrating microfibers with few-layer gallium selenide crystals, enabling controlled and broadband optical frequency mixing. We reveal the critical role of time-domain synchronization in sum-frequency generation (SFG) and demonstrate multi-frequency mixing from four continuous-wave sources, producing ten converted wavelengths through simultaneous second-harmonic generation (SHG) and SFG. Remarkably, the system operates at low excitation thresholds, supporting broadband SFG with two superluminescent diode sources and yielding an unprecedented SHG continuum extending to ~180 nm with a supercontinuum source. Furthermore, the broadband SFG spectrum can be tuned over 70 nm by coupling with a quasi-monochromatic laser. This approach establishes a scalable and versatile platform for regulating the wavelength and bandwidth of nonlinear processes in optical fibers, opening pathways toward tunable broadband light sources and advanced all-fiber photonic technologies.

Uncooled mid-infrared lead-salt photodetectors are considered promising candidates for next-generation infrared optoelectronic devices that meet the small size, low weight, high performance, low power consumption, and low price (SWaP(3)) standards. However, research on the internal charge transport mechanisms of these devices is currently very limited, resulting in a lack of deep understanding of the key transport mechanisms, which seriously hinders the development of uncooled mid-infrared photodetectors. Here, high-performance uncooled PbSe photodetectors with different iodine contents were fabricated, achieving a high specific detectivity of 1.68 & times; 10(10) Jones at 300 K. Through the temperature dependence of the conductivity, the charge transport mechanisms at different temperatures were revealed, showing that at low temperatures, charge transport follows the variable-range hopping mechanism, whereas near room temperature, grain boundary barrier transport dominates, with a transition temperature of T-c = 217.4 K. A grain boundary transport model for charge carriers was proposed, revealing the regulatory effect of iodination on the device's grain boundary barriers. The study also investigated the space charge effects within the devices, diffusion currents, and electron tunneling characteristics, uncovering for the first time the space charge-limited transport mechanism and the Poole-Frenkel effect under high bias conditions. The findings provide new insights into device physics for high-performance uncooled lead-salt photodetectors.

Significant research efforts have focused on developing novel optoelectronic devices utilizing two-dimensional (2D) transition-metal dichalcogenides (TMDs), motivated by their strong light-matter interactions and unique material properties. Photodetectors simultaneously achieving high-speed and high-responsivity performance are particularly crucial for applications such as high-data-rate interconnects operating at telecom wavelengths. However, the intrinsically limited carrier mobilities in TMDs present a fundamental bottleneck for a high-speed operation. Here, we demonstrate high-performance monolayer MoS2 photodetectors fabricated via chemical vapor deposition (CVD) and monolithically integrated with a dielectric waveguide. The Au-MoS2-Au device architecture minimizes carrier transit path lengths while exploiting the short lifetime of hot electrons, yielding a measured bandwidth of similar to 3.28 GHz. Concurrently, the device achieves a high responsivity of 144 mA W- 1 at 1529.3 nm, attributed to an integrated tapered-waveguide design that significantly enhances the light-matter interaction region. This in situ synergistic integration of wafer-scale CVD-grown TMDs with planar, etch-free photonic circuits establishes a versatile platform for realizing high-performance on-chip optoelectronic devices.

Surface plasmon resonance (SPR) has been applied in many fields such as bio-detection and chemical analysis. SPR holographic microscopy (SPRHM) demonstrates the possibility of characterizing tiny samples based on simultaneous SPR intensity-and phase-contrast imaging. However, the "tail" effect caused by transverse propagation of surface plasmon wave greatly limits the development of SPR-related technologies. Although effective, the current solution introducing azimuthal scanning excitation has low temporal resolution, hindering fast and real-time imaging. In this paper, we propose a subsampling method based on compressive sensing to enhance the temporal resolution of azimuthal scanning excitation SPRHM. Image reconstruction procedure is designed and used for subsampled SPR intensity-and phase-contrast images of different samples. By solving optimization problems, the "tail" effect can be effectively and efficiently removed, without affecting imaging and measurement of samples. Experiment results indicate that the subsampled reconstructed images maintain high quality and fewer required images. The original image acquisition time of 25 s is reduced to 1-2 s, thus facilitating fast imaging and reconstruction. The proposed method will significantly improve technical limitations of SPRHM and expand the range of potential application targets.

ABSTRACT While advancements in optical fiber‐based second harmonic generation (SHG) have leveraged novel waveguide designs and two‐dimensional nonlinear material integration, conventional fiber schemes remain constrained by limited multi‐frequency control and restricted efficiency growth. We demonstrate an all‐fiber resonant SHG strategy achieving periodic enhancement and polarization modulation by integrating a few‐layer GaSe crystal with a microfiber knot resonator (MKR). Benefitting from MKR‐enabled resonant interaction with GaSe, which possesses ultrahigh second‐order nonlinear susceptibility, the maximum excitation of comb‐like SHG at resonant wavelengths achieves a 32‐fold enhancement compared to GaSe‐microfiber integration under continuous‐wave laser pumping. Meanwhile, the twisted MKR structure facilitates dynamic polarization‐dependent control of the split SHG wavelengths through pump polarization modulation. Experimental results further reveal distinct intensity patterns of SHG intensity in both under‐coupling and over‐coupling regimes. Our findings offer insights into accessing broad, efficient, polarization‐controllable SHG combs for multifunctional nonlinear photonic devices with on‐demand spectral tailoring capabilities.

Chalcogenide polymeric materials have emerged as promising, cost-effective alternatives to conventional infrared materials. In this Letter, we demonstrate the fabrication of micro-optics elements using a flexible chalcogenide polymer with an extended transparency window into the long-wave infrared region. Employing this thermoset S-DADS polymer, broadband infrared micro-optical components were fabricated via casting processes. Experimental results validate their functionality in IR imaging, wavefront sensing, and mechanically tunable beam shaping, which shows their potential for diverse infrared applications.

Uncooled mid-wave infrared (MWIR) photodetectors are an important development direction for next-generation infrared technology. However, due to the narrow bandgap and thermal noise, MWIR photo-detection is difficult to achieve with conventional photoconductive (PC) and photovoltaic (PV) photodetectors. This paper proposes a low-damage design based on O+ ion implantation in PbSe, achieving enhanced MWIR photoconductive response. The surface morphology of the nanostructures was observed. The optical bandgap of the thin films became smaller, making them more suitable for mid-infrared radiation detection. Increasing the implantation dose reduced the Urbach energy from 136.9 to 53.37 meV, indicating a reduction in band tail disorder and shallow defect states. An optimal dose (1 & times; 10(18) cm(-2)) achieved a peak responsivity of 2.1 A/W at a wavelength of 4 mu m, with a detectivity of 2.3 & times; 10(9) Jones at 4 mu m, 300 K under bias voltage of 15 V, and chopping frequency of 400 Hz. The photoresponse is attributed to the formation of a built-in carrier separation region and the generation of deep-level traps, thereby enhancing carrier separation and prolonging minority carrier lifetime. Additionally, extremely high carrier mobility (4480-8320 cm(2) V-1 s(-1)) was achieved, which improves the collection efficiency of photogenerated carriers. This work demonstrates a defect engineering strategy through O+ implantation, achieving excellent carrier mobility and responsivity for the high-performance uncooled MWIR photodetector.

Fiber Bragg gratings (FBGs) with significantly enhanced reflectivity in ring-core fibers (RCFs) were successfully inscribed by using a high-repetition-rate femtosecond laser and the ring-by-ring (RbR) method. In comparison to FBGs with very low reflectivity produced in RCF through point-by-point or line-by-line methods, those inscribed via the RbR method exhibit an improved reflectivity of up to 80% . This enhancement is attributed to the alignment of the refractive index modulation trajectory with the mode field distribution of the RCF. To further increase the overlap area, a multi-layer RbR method was employed, achieving near-complete coverage of the fiber core and thereby enhancing the reflectivity to 98.8% . Although the signal-to-noise ratio of the FBGs reaches over 30 dB, due to the strong high-frequency components in the frequency domain of the uniform refractive index modulation, the side-mode suppression ratio (SMSR) is less than 10 dB. Therefore, two novel apodization techniques - one involving diameter variation and the other arc-length variation - which are compatible with the RbR method are proposed and demonstrated. By precisely controlling the diameters or arc-lengths of each ring induced by femtosecond laser, diverse apodization modulation profiles can be achieved to inscribe apodized FBGs with a SMSR of more than 25 dB. Four types of FBGs using different apodization functions were compared and analyzed, the experimental results show that the Gaussian function has the optimal apodization effect.

Metasurfaces enable full degrees of freedom (DOFs) of Jones matrix control on a 2D planar platform, but even when all four complex elements are accessible, the number of independently addressable channels remains insufficient for high-dimensional multiplexing. Here, a diffraction-order-decoupled metasurface framework is proposed to effectively exploit the DOFs of the Jones matrix across multiple diffraction orders, enabling independent multi-DOF control for each order. In the orthogonal linear polarization bases, independent six DOFs of Jones matrix control are achieved for the first- and second-order diffraction channels, and three near-field nanoprinting images together with three far-field vectorial holographic images are experimentally reconstructed in each diffraction order. Moreover, the Jones description is extended to an orthogonal elliptical polarization base, which breaks the numerical equivalence of the off-diagonal elements imposed in the linear polarization bases and thereby unlocks full control over all Jones elements for each diffraction order, enabling full-DOF Jones matrix multiplexing across multiple diffraction orders. Furthermore, diffraction-order decoupling is extended to two orthogonal in-plane directions, enabling four diffraction channels with distinct polarization responses. The proposed approach establishes a general route to high-capacity multiplexing of polarization and diffraction and supports applications in optical encryption, multidimensional vectorial encoding, and high-density optical information processing.

Plasmon-exciton coupling effect plays a crucial role in light emission and quantum control, which, however, has not been reported in nonmetallic systems until now. Topological insulators (TIs), with breaking through the limitations of traditional metallic materials on the operating frequency range and photonic integration, offer a new platform for exploring surface plasmons and their interaction with matter. Herein, we experimentally demonstrate the scattering resonance response of surface plasmons in the antimony telluride (Sb2Te3) TI metasurfaces with focused ion beam (FIB)-fabricated nanowells as well as the coupling behaviors between the plasmons and excitons in atomic-layer tungsten disulfide (WS2) semiconductors. The measured results show that the wavelength of scattering resonance presents a redshift with increasing the depth and pitch of TI nanowells. In WS2/TI metasurface heterostructures, we observe the obvious coupling effect between the TI plasmons and excitons in WS2 atomic layers. The theoretical analysis reveals that the plasmon-exciton interaction is located in the weak coupling regime with the generation of Fano resonance, inducing strong photoluminescence (PL) enhancement of WS2 atomic layers. This work will open a new door for plasmon-exciton coupling and applications of TIs in compact optoelectronic devices.

The optical characterization of atomic-layer materials requires the quantitative determination of both their complex refractive indices (RIs) and thickness. However, existing methods rely on preset thicknesses, empirical models, or auxiliary characterization tools. It remains a challenge to jointly retrieve real part n, imaginary part k, and thickness d of ultrathin samples in a wide-field manner and over a broad measurement range. Here, we propose an angle-scanning surface plasmon resonance (SPR) holographic microscopy. This method utilizes the modulation effect of sample parameters (n, k, d) on SPR phase shifts and retrieves them by fitting measured phase shifts with theoretical counterparts at multiple angles. Measurements of monolayer, bilayer, and multilayer graphene samples validate the effectiveness of this method and demonstrate its broad measurement range from monolayer to tens of nanometers. A step-like sample further confirms its wide-field measurement capability. This work provides an optical approach for jointly characterizing the complex RIs and thickness of graphene, with potential applicability to other atomic-layer materials.

In monolayer semiconductors, excitons confined by strain-induced potential traps are promising candidates for on-chip single-photon sources. For these quantum emitters, achieving broadband tunability while preserving high brightness is crucial for quantum information processing and communication, but remains challenging in aligning the emitter energy with optical resonances. Here, we demonstrate resonant tuning of localized exciton emission in monolayer WSe2 using an Au nanocube-on-mirror nanocavity. The design enables simultaneous strain-induced exciton energy tuning and Purcell-enhanced emission. By adjusting the cavity gap, it allows precise spectral alignment of the localized exciton with the plasmonic resonance. We observe a record-large redshift over 240 meV in localized exciton energy. Compared with the conventional approach, a 22-fold enhancement in emission intensity is achieved due to the spectral, spatial, and polarization matching between the localized exciton and plasmons. Our findings establish a robust strategy for developing high-performance nonclassical light sources, facilitating the development of scalable quantum applications.

The noise-like pulses in fiber lasers are incoherent clusters of disordered femtosecond subpulses, with a focused interest in the low-coherence light source and its related applications. However, whether the noise-like pulse can sustain its low-coherence feature still remains a fundamental question that is significant to understanding the nonlinear dynamics and to controlling the coherence of the noise-like pulse. Here, we report unveiled dynamics where the noise-like pulse intermittently evolves into the coherent dissipative soliton and subsequently recovers to the original noise-like pulse-a process opposed to the soliton explosion. Our results may guide the optimal design of ultrafast lasers and contribute to a better understanding of the complex dynamics of nonlinear waves.

With the emerging significance of metasurface-based multidimensional optical sensing, most demonstrations have been limited to coherent-light conditions. This study proposes an incoherent multidimensional imager that performs preliminary processing at the optical front end through point-spread-function (PSF) engineering of a metalens. By leveraging the Pancharatnam-Berry (PB) phase for angle and polarization multiplexing, this multidimensional imager splits the positive and negative convolution operations of a Laplacian operator into separate channels. This enables simultaneous edge detection and partial Stokes parameter measurement with minimal back-end electronic computation under an incoherent light. We experimentally demonstrate single-shot edge detection and polarization analysis for spoof and real fingerprints under LED illumination, enabling their effective discrimination. This multidimensional imager applicable to incoherent conditions opens new possibilities for applications such as biometrics and security.

Humidity performance of perovskites is critical for efficient fabrication and large-scale application of light-emitting devices as it directly influences the material stability, film quality and device lifespan. Herein, we propose an all-fiber strategy for dynamic monitoring of the humidity-induced perovskite/polyacrylonitrile (PAN) composite nanofibers. Pure-bromide quasi-2D perovskite nanocrystals are in situ synthesized and encapsulated in the PAN matrix on the optical fiber platform via an electrospinning technique, which ensure the luminescence stability of the materials in relative humidity (RH) above 50%RH. By wrapping the composite nanofibers around an excessively tilted fiber grating (Ex-TFG) to serve as a humidity-sensitive film, water molecules can rapidly penetrate the nanofiber matrix and interact with the perovskite material, allowing the transmission spectrum of the grating to accurately quantify their concentrations. Experimental results show that the humidity-induced variations in the complex permittivity of the quasi-2D perovskite/PAN composite nanofibers directly reduce the resonant amplitude of the transmitted modes of the Ex-TFG, achieving a top intensity sensitivity of 0.63 dB/%RH. This study introduces an efficient method for incorporating stable perovskites onto fiber-based devices, and also demonstrates a potential for humidity characterization of the luminescent materials through the real time fiber signal monitoring.

Quantitative phase imaging (QPI) in the near field is a powerful tool for visualizing nanoscale structures in low-dimensional materials, dielectric mixtures and biological cells. Although near-field QPI offers extremely high sensitivity, phase aberrations of the optical system can pose serious limitations. Overcoming these problems, we introduce an adaptive optics approach that takes advantage of the complex amplitude measured by digital holographic microscopy (DHM). By using a spatial light modulator as a beam shaping device, our method allows for in-situ , accurate, fast and flexible aberration correction by quantifying wavefront distortions in terms of Zernike modes, and pre-compensating them with a spatial light modulator. For validation, we demonstrate near-field phase imaging with adaptive-optics surface plasmon resonance holographic microscopy (AO-SPRHM) on microstructured test samples and live cells. With a total correction time below 1 s, background-free time-lapse imaging over many hours becomes feasible. The approach can be easily transferred to other phase imaging techniques, including transmission, reflection and total internal reflection DHM as well as related modalities.

ABSTRACT The development of reconfigurable photonic devices demands dynamic, non‐invasive control of nonlinear optical processes at the nanoscale. While second‐harmonic generation (SHG) in 2D materials (e.g., MoS 2 ) is a promising candidate, its active modulation remains challenging. Here, we report an all‐optical strategy for on‐demand writing and erasing of SHG in few‐layer MoS 2 . By alternating ultraviolet‐ozone treatment and continuous 532 nm laser irradiation, we achieve fully reversible, cyclic modulation of the SHG intensity exceeding 80‐fold. Our comprehensive spectroscopic and microscopic characterizations indicate that the tunability arises from the metastable formation and removal of surface S─O bonds, which transiently break lattice inversion symmetry. Leveraging this reversible control, we demonstrate spatially selective patterning of SHG, enabling the writing, erasing, and rewriting of optical information on a single MoS 2 flake. This work establishes a simple, non‐destructive platform for reconfigurable nonlinear photonics, with direct implications for optical memory, logic, and encryption technologies.

Solitons circulating in nonlinear resonators can exhibit diverse instabilities, among which period doubling (P2) is a universal route to breathing dynamics and chaos. To date, P2 in optical systems has been attributed primarily to nonlinear effects. Here, we demonstrate that strong linear mode coupling (LMC) between the two polarization components of a vector soliton can also drive a robust P2 state in a fiber laser. As the coupling strength increases, the breathing frequency of the vector soliton continuously rises and eventually locks to half the laser repetition rate, i.e., the pulse recovers to its original state with every two cavity roundtrips. In the P2 regime, the dominant energy alternates between the two polarization components because of strong LMC, leading to pronounced P2 oscillations in the individual components, while the total vector soliton exhibits only a weak P2 signature. Moreover, under the combined action of LMC and intramodal time shift, each polarization component switches periodically between single-pulse and dual-pulse states. These results identify LMC as a distinct and controllable route to P2 dynamics in vector solitons and provide insight into the stability and chaos of ultrafast lasers.