ABSTRACT Ensuring stability and controlling terahertz spintronic emitters typically involves the application of a relatively strong magnetic field to counter magnetization drift during repeated pumping to regulate the emitted terahertz radiation's direction. However, using a strong magnetic field is practically not relevant for on‐chip compact, low‐cost ultrawide broadband terahertz opto‐spintronic devices. Uniaxial magnetic anisotropic materials provide a potential avenue to stabilize as well as control the ultrafast spin current pulses, at weak magnetic field specifically weaker than the anisotropy field. Here, we report the amplitude modulation as well as polarization switching of the terahertz spin current pulse at magnetic field less than 1 Oe, demonstrating an ultrasensitive spintronic emitter. In comparison to the use of a strong magnetic field, our repeated measurements demonstrate that there is no magnetization drift, rendering the need for a strong magnetic field unnecessary. Our findings establish a uniaxial magnetic anisotropic emitter with ultra‐strong modulation as a promising candidate for future efficient ultrafast on‐chip opto‐spintronic devices.
ABSTRACT Efficient and polarization‐switchable on‐chip mid‐infrared light sources are desirable for portable and miniaturized systems for applications in gas sensing, free‐space optical communications, and imaging. The polarization‐switchable function can offer a new information dimension for signal processing. Black phosphorus (BP), with perfect linear dichroism, high internal quantum efficiency, and a narrow bandgap of 0.3 eV, is a promising candidate for polarization‐switchable on‐chip mid‐infrared light sources. Here, we demonstrate an electrically pumped, robust, and polarization‐switchable mid‐infrared light emission in a twisted BP structure. Through introducing an oxidized phosphorus interface between the top and bottom BP layers to engineer the energy band alignment and controlling BP crystalline orientations, the mid‐infrared emission can be electrically pumped, and light polarization states can be switched between top and bottom BP layers by simply changing the polarity of the applied bias. The phenomenon can be observed in a wide twisted angles up to 90°. Delicate peak external quantum efficiencies of 0.28% and 4.87% are achieved at 300 and 80 K, respectively. Moreover, an optical logic operation strategy based on the polarization‐switchable light emission property is demonstrated.
ABSTRACT Developing quantum materials for electronic devices, including neuromorphic computing, is a rapidly expanding field. Vanadium dioxide (VO 2 ) is a prototypical correlated oxide known for its sharp, reversible insulator‐to‐metal transition (IMT), making it a compelling platform for reconfigurable electronics. Controlled defect formation, such as focused Ga + ion beam irradiation, can influence the IMT in VO 2 , yet the associated nanoscale phase behavior and switching mechanisms remain largely unexplored. Here we introduce spatially localized defects in VO 2 using focused Ga + irradiation with tunable dose and probe the resulting thermal‐ and voltage‐driven IMT using infrared and terahertz near‐field nano‐imaging. Focused Ga + irradiation alters, and often suppresses, phase switching behavior, localizing the conductive pathway and reducing switching power for energy‐efficient neuromorphic functionality. Compared to pristine VO 2 , the irradiated material exhibits suppressed IMT behavior, with lower resistivity below the transition temperature but higher resistivity above it. Varying irradiation dose modulates this suppression, impacting filamentary nucleation. Devices with lightly irradiated regions localize the resistive switching behavior, whereas heavily irradiated regions remained inactive during switching, with neighboring pristine material switching into the metallic phase instead. These findings reveal selective ion irradiation enables local control of the IMT in VO 2 , offering a scalable route to programmable, energy‐efficient neuromorphic devices.
ABSTRACT ZnSeTe quantum dot light‐emitting diodes (QLEDs) are promising candidates for environmentally friendly display applications. However, their electroluminescence performance and practical implementation are still hindered by nonradiative recombination originating from exciton trapping at defect states among quantum dots (QDs) in the emissive layer (EML). Herein, wide‐bandgap ZnS nanocrystals are incorporated into the ZnSeTe EML to suppress nonradiative recombination and modulate carrier transport, thereby improving the performance of blue ZnSeTe QLEDs. The results reveal that the introduction of ZnS nanocrystals effectively suppresses Förster resonance energy transfer among QDs within the EML, leading to an extension of the exciton lifetime in the film from 9.2 to 12.7 ns. Meanwhile, the built‐in electric field established at the interface between ZnS nanocrystals and ZnSeTe QDs induces upward band bending in the EML, which lowers the hole injection barrier and facilitates more balanced carrier transport. As a result, the resulting blue QLEDs deliver a luminance of 10229.4 cd m −2 at 6 V, a maximum external quantum efficiency of 21.2% at 2317.4 cd m −2 , and a T 50 lifetime of 220.2 h at an100.0 cd m −2 , compared with 49.9 h for the control device. This work offers an effective strategy for developing high‐performance blue environmentally friendly QLEDs.
ABSTRACT The quest for resilient photodetectors in flexible electronics is met with the challenge of perovskite instability under mechanical stress and environmental conditions. This study introduces a Cs 3 Cu 2 I 5 /poly(N‐vinylcarbazole) (PVK) photodetector on paper, where PVK not only encapsulates Cs 3 Cu 2 I 5 to shield it from environmental degradation but also synergistically enhances photoconductive properties. The device exhibits a responsivity (R) of 1.35 A/W, remains stable operation after 5000 bending cycles, and retains 75% of its initial performance following 215 days of exposure.
ABSTRACT Recent advances in sulfur polymer chemistry of elemental sulfur (S 8 ) feedstocks have enabled the emergence of a new class of plastic optical glasses spanning applications from visible (VIS) wavelength photonics to long‐wave infrared (LWIR) imaging. In contrast to conventional optical polymers, S 8 ‐derived polymers exhibit elevated refractive indices, broadband optical transparency, and favorable processing characteristics. This mini‐review summarizes recent developments in sulfur‐derived plastic optical glasses prepared through inverse vulcanization (IV) and sulfenyl chloride inverse vulcanization (SC‐IV) polymerizations. Inverse vulcanized glass (IVG) prepared from ultra‐high purity elemental sulfur afforded novel broadband VIS–LWIR plastic optics with high refractive index (RI, or n ≈ 1.9) and covalent adaptable network behavior. Extension of sulfur polymer chemistry to disulfide glass (DSG) materials derived from sulfur monochloride (S 2 Cl 2 ) enabled precision optical manufacturing of VIS‐IR transparent thermosets exhibiting reduced visible coloration, low optical attenuation, and compatibility with precision optics fabrication. Further development of photocurable disulfide methacrylate resin (DSMR) systems afforded a high refractive index photopolymer disulfide glass (Photo‐DSG) compatible with UV curing, microfabrication, and vat photopolymerization 3D printing workflows. These demonstrations establish sulfur‐derived polymers as a broader family of manufacturable plastic optical glasses bridging commodity sulfur feedstocks with emerging optical and photonic manufacturing technologies.
ABSTRACT Extending dual‐ or multi‐band wave plates to the terahertz regime remains challenging due to the complex design of high‐efficiency metasurfaces and the scarcity of scalable, low‐cost fabrication techniques. Here, we overcome this limitation by demonstrating a dual‐band metasurface‐based half‐wave plate (HWP) with an out‐of‐plane triple‐bar design, where single‐ and double‐bar pillars are vertically stacked at distinct heights within a single meta‐atom. Simulations reveal that the low‐frequency band is primarily governed by magnetic resonances of the single‐bar pillar, while the high‐frequency band arises from hybrid magnetic‐electric resonances involving the double‐bar pillars. The HWPs are fabricated using a simple projection micro‐stereolithography (PµSL) 3D printing technique. Experimental results show a polarization conversion ratio exceeding 90% across 0.33–0.78 THz (fractional bandwidth, FBW = 81.1%) and 1.29–1.81 THz (FBW = 33.5%). Moreover, by simply tuning the pillar height, the same platform yields quarter‐wave plate behavior with ellipticity exceeding 0.8 across 0.49–0.83 THz (FBW = 51.5%) and below ‐0.8 across 1.14–1.85 THz (FBW = 47.5%). This out‐of‐plane metasurface approach, combined with a simple 3D printing process, establishes a scalable paradigm for high‐performance, low‐cost, and compact THz wave plates.
ABSTRACT Narrowband organic light‐emitting diodes (OLEDs) have attracted growing interest, with remarkable progress achieved in the blue/green/red spectral regions. In contrast, realizing narrowband near‐infrared (NIR) OLEDs remains both crucial and challenging. In this work, we present a class of narrowband NIR fluorescent emitters featuring dual boron‐dipyrromethene (BODIPY) cores, reinforced by a hydrogen‐bonding‐locked strategy to achieve spectral purity. The proposed strategy increases molecular rigidity and narrows the full‐width at half‐maximum (FWHM) by suppressing stretching/scissoring vibrations. The proof‐of‐concept emitter αα‐BDP 2 exhibits narrowband NIR emission centered at 713 nm with a FWHM of only 31 nm (0.076 eV), while ββ‐BDP 2 achieves an exceptionally high photoluminescence quantum yield (PLQY) of 98% in toluene solution. By employing the developed BODIPY‐derived materials as terminal emitters, solution‐processed narrowband NIR OLEDs have been assembled with external quantum efficiency as high as 2.7% at 713 nm with FWHM of 55 nm. This work, according to the knowledge, represents one of the best instances of solution‐processed narrowband NIR OLEDs based on typical fluorescent emitters.
ABSTRACT The ability to store and release charge carriers in response to external stimuli is fundamental to advanced technologies in radiation detection, imaging, and sensing. However, combining good sensitivity with multimodal functionality in a single material has remained challenging. Here we report that Mn 2+ ‐doped Cs 3 Cd 2 Cl 7 exhibits dual‐mode charge storage depending on the stimulation pathway. Under X‐ray irradiation, the material stores energy in multiple defect states, producing six thermoluminescence (TL) glow peaks between 141 and 450 K. The integrated TL intensity is ∼4.7 times higher than that of the commercial X‐ray storage phosphor BaFBr(I):Eu 2+ , demonstrating good sensitivity suitable for temperature‐resilient radiography. In contrast, mechanical grinding of the same crystals in an agate mortar induces a distinct charge trapping behavior, generating two TL peaks at approximately 445 and 607 K. This force‐induced charge storage enables the recording of mechanical events for delayed readout, offering a pathway for non‐real‐time force sensing. The same material thus serves dual functions, delivering bifunctional X‐ray imaging and mechanical force recording through distinct energy release pathways. Our findings establish Cs 3 Cd 2 Cl 7 :Mn 2+ perovskite as a stimuli‐responsive platform and open opportunities for multimodal sensing technologies where both radiation and mechanical histories can be stored and retrieved on demand.
ABSTRACT Dual‐wavelength fiber lasers operating in the 1.0 µm band are of significant interest for applications such as optical frequency synthesis, differential absorption sensing, and multi‐band lidar. However, achieving independently controllable dual‐wavelength emission in a single fiber remains challenging due to ion‐ion interactions and system complexity in conventional co‐doped or multi‐source approaches. In this work, we demonstrate a spatially partitioned doped fiber (SPDF) with a double‐semicircle Yb 3+ ‐ and Nd 3+ ‐doped silicate glass core, in which the two active ions are confined to physically separated semicircular regions within a common core. This spatial partition helps suppress inter‐ion energy transfer while enabling selective excitation using 976 nm pumping for Yb 3+ and 808 nm pumping for Nd 3+ . Using a compact 3.5 cm SPDF segment, switchable laser outputs at 1034 and 1064 nm are achieved, demonstrating independent wavelength control with negligible cross‐response between the two pump channels. This finding indicates that spatial partitioning provides a compact and practical route for independently controllable dual‐wavelength fiber lasers and enables integration into miniaturized fiber laser systems.
ABSTRACT Lithium niobate on insulator (LNOI) has emerged as a promising platform for photonic integrated circuits due to its strong electro‐optic, piezoelectric and nonlinear properties. The incorporation of rare‐earth ions, particularly erbium (Er 3+ ), enables potential functionalities such as quantum memory and single‐photon emission in the telecom band. This study presents a method for the Er 3+ doping of X‐cut LNOI using a focused ion beam (FIB) implantation system with sub‐100 nm spatial precision, demonstrating the ability to dope optically emitting rare‐earth ions into this technologically relevant platform. Photoluminescence (PL) studies of doped regions reveal characteristic emission consistent with bulk Er‐doped lithium niobate. The PL temperature dependence is studied from 300 to 5 K. The emission exhibits conventional behavior down to approximately 50 K, followed by a marked decrease in the emission intensity and lifetime at lower temperatures. This anomaly is suggested to relate to a suppression of the pyroelectric response in LiNbO 3 below 50 K, which affects the local electric field and consequently could modify the Er 3 + emission. The results demonstrate a method for targeted Er 3+ doping into the most widely used cut of LNOI for integrated photonic devices and provide further important considerations for their exploitation in cryogenic quantum devices.
ABSTRACT Luminescence resonance energy transfer (LRET) is highly sensitive to the donor–acceptor distance, rendering the geometry of the donor critically important. Conventional upconversion nanoparticles (C‐UCNPs, based on β‐NaYF 4 as the host) exist as isotropic spheres, wherein only the near‐surface activators contribute to LRET. Although the core–shell design can reduce the donor–acceptor distance, it requires complex multistep synthesis with careful shell control. In this study, distance‐confined ultrathin upconversion nanoplatelets (DC‐UCNPLs, based on Cs 2 NaYF 6 as the host) with sub‐10 nm thickness are reported. In this system the platelet geometry positions the majority of activators within the Förster distance, inherently favoring distance‐confined LRET (DC‐LRET). As a result, the DC‐UCNPLs exhibited a 4.3‐fold higher acceptor‐to‐donor emission ratio than the C‐UCNPs; Monte Carlo simulations confirmed this intrinsic advantage. In the reverse configuration, where IR‐806 acted as a donor and the DC‐UCNPLs as acceptors, the process was defined as reverse distance‐confined LRET (RDC‐LRET), corresponding to dye‐sensitized upconversion. This yielded an extraordinary 1471‐fold increase in upconversion luminescence under 808 nm excitation. Overall, these DC‐UCNPLs establish a structurally uniform, scalable, and bidirectional donor–acceptor architecture, thereby offering a powerful strategy for next‐generation nanoprobes in bioimaging, sensing, and energy conversion.
ABSTRACT We demonstrate a compact approach for generating 2‐cycle mid‐infrared pulses centered at 2.038 µm using bulk TiO 2 plates for nonlinear spectral broadening and self‐compression. Starting from a passively CEP‐stable idler pulse produced by an optical parametric amplifier, the beam is transmitted through a sequence of three 500 µm‐thick TiO 2 plates operated near the material's zero‐dispersion wavelength. The pulse duration is reduced from 103.9 to 14.1 fs without subsequent dispersion‐compensation stages, while the spectral bandwidth broadens from 10.85 to 84.42 THz and the output pulse energy is 42 µJ, corresponding to 76.3% transmission efficiency. The compressed output exhibits a CEP standard deviation of 334 mrad over a 50 min measurement. These results establish bulk TiO 2 self‐compression as a simple and scalable platform for generating mid‐infrared few‐cycle pulses.
ABSTRACT Polarization‐sensitive photodetectors operating in the O‐band spectrum are essential for advanced optoelectronic applications. However, mostly metal halide perovskite photodetectors lack intrinsic polarization sensitivity and are typically limited to the UV–vis spectrum by their bandgaps. Here, O‐band spectrum polarization‐sensitive photodetection is firstly achieved by integrating an erbium‐doped bimetallic perovskite Cs 2 NaBiI 6−y Cl y :Er with energy‐flux‐weighted absorption (EFWA) designed metallic gratings. This design enables effective light field confinement and maximal absorption within the perovskite layer by selectively excite a transverse electric (TE) guided‐mode resonance (GMR) at 1310 nm, resulting in a polarized absorption of 16.14%, corresponding to a 6.86‐fold enhancement compared with their planar counterpart. Experimentally, the photodiode exhibited a record polarization anisotropy ratio of 2.31 at 1310 nm which is the longest wavelength reported so far, a responsivity of 2.14 × 10 −2 mA W −1 , and a detectivity of 1.02 × 10 7 Jones. This work provides a useful strategy to overcome the polarization discrimination limitation of perovskite photodiodes in O‐band spectrum.
ABSTRACT Artificial intelligence has revolutionized optical device design, overcoming the efficiency bottlenecks of traditional methods. For holographic metasurfaces, conventional iterative algorithms suffer from time‐consuming iterations and convergence stagnation, especially as the complexity of 3D target fields increases. While deep learning‐based algorithms have improved the trade‐off between speed and image quality, most existing models remain constrained by predefined physical scenarios. To address these challenges, we develop LM‐PINN, a physics‐informed neural network that integrates local polynomial fitting with multi‐plane wave propagation, for the rapid design of terahertz 3D holographic metasurfaces. Through self‐supervised training, LM‐PINN enables direct end‐to‐end mapping from target holographic patterns to metasurface structures within a predefined holographic configuration, without labeled datasets. Both simulated and experimental results from LM‐PINN demonstrate higher imaging quality than traditional iterative algorithms. We further incorporate distance encoding into LM‐PINN, yielding Dist‐LM‐PINN. Dist‐LM‐PINN enables a single trained model to generalize across varying diffraction distances and demonstrate 2D/3D holographic scenarios without retraining by utilizing the precomputed electric‐field distributions at the metasurface plane as inputs. The proposed framework typically completes inference in less than 1 second, providing a multifold speed advantage over traditional algorithms and offering a fast and flexible framework for high‐quality, real‐time, and large‐scale 3D holographic technologies.
ABSTRACT Y 2 O 3 ‐MgO composite ceramics possess intrinsic advantages in the 3–5 µm mid‐infrared region, including theoretically high transmittance, high mechanical strength, and low emissivity, making them promising candidates for next‐generation infrared window materials for high‐speed flight applications. However, further process optimization is still required to improve their practical performance. In this study, YM composite powders were prepared via the glycine‐nitrate combustion method. A fluorination strategy was introduced for the first time through ball milling during powder processing. Combined gravimetric water vapor adsorption measurements and first‐principles calculations revealed that fluorination enhances the hydrophobicity of the powders, thereby improving resistance to moisture absorption of MgO. Sintering kinetics analysis further demonstrated that an appropriate level of fluorination promotes densification, suppresses grain growth, and consequently improves infrared transmittance. Overall, 0.05 wt% fluorination increases powder hydrophobicity by nearly 20%, enables a transmittance exceeding 80% in the 3–5 µm range, and achieves an average flexural strength of 375 MPa. To the best of our knowledge, this is the first systematic study on the preparation of fluorinated YM composite ceramics, providing a new perspective for processing optimization of this ceramic system.
ABSTRACT Metal halide perovskites are promising materials for optoelectronic applications owing to their outstanding optical and electronic properties. Among them, all‐inorganic perovskites such as offer superior thermal and chemical stability. However, obtaining high‐quality thin films via solution processing remains challenging due to the low solubility of the precursor, and current additive or solvent engineering strategies are often complex and poorly reproducible. High‐pressure recrystallization has recently emerged as a promising route to improve film quality, yet its impact on film properties remains insufficiently explored. Here, we systematically investigate the morphological, structural, and optical properties of thin films prepared by high‐pressure recrystallization, in comparison with standard non‐recrystallized films. Optimized recrystallization at 300 bar produces smooth, pinhole‐free, single‐phase 3D perovskite layers with sub‐nanometer roughness, while the film thickness is precisely tunable via precursor concentration. The process enhances both grain and crystallite sizes, leading to amplified spontaneous emission with a reduced excitation threshold and improved photostability. Temperature‐dependent X‐ray diffraction further reveals the orthorhombic–tetragonal–cubic phase transition, consistent with single‐crystal behavior. This study provides fundamental insights into pressure‐driven recrystallization and establishes a reproducible, scalable approach for fabricating high‐quality films for optoelectronic devices.
ABSTRACT Redox‐tunable conducting polymers have emerged as promising materials for dynamic plasmonics and metasurfaces. However, only a few conducting polymers with particularly high conductivities (>1000 S/cm) have been reported to provide spectral regions with plasmonic behavior. Here, we use polypyrrole (PPy) as a model system to address whether optically metallic properties can also be generated in conducting polymers with moderate conductivity (around 110 S/cm). We found that the material possesses negative permittivity but only in a limited spectral region and with magnitude limited to below 2. Furthermore, the negative permittivity region originates primarily from a polaronic absorption band rather than purely from mobile carriers as in conventional plasmonic materials. Nanostructures made from the material exhibit size‐dependent optical extinction peaks despite not fulfilling the traditional quasistatic resonance condition. These peaks, denoted as quasi‐resonances, can be reversibly tuned by electrochemical modulation, analogous to those presented in conducting polymer plasmonic nanostructures.
ABSTRACT Carbon‐dot‐based luminescent films offer a low‐toxicity and solution‐processable alternative to conventional quantum‐dot emitters, but their implementation as solid‐state photonic films with controlled light extraction remains challenging. Here, we demonstrate nanopatterned dual‐carbon‐dot/poly(vinyl alcohol) (CD/PVA) films for enhanced directional light outcoupling. Blue‐emissive carbon dots (B‐CDs) and green‐emissive carbon dots (G‐CDs) were synthesized by microwave‐assisted carbonization and incorporated into water‐processable PVA matrices. The two CDs exhibited distinct heteroatom compositions, surface bonding configurations, and blue/green photoluminescence characteristics. Drop‐cast and spin‐coated films confirmed composition‐dependent blue–green emission in the solid state, while mixed B‐CD/G‐CD films showed spectral evolution and lifetime changes influenced by the coexistence of the two CD species. Nanoimprinted CD/PVA films with periodic surface structures produced angle‐dependent emission peaks under 355 nm Nd:YAG laser excitation, and the measured peak positions agreed with the calculated first‐order diffraction condition. Reference‐normalized emission analysis revealed approximately six‐fold relative angle‐dependent spectral enhancement at the calculated outcoupling angles in B‐CD‐rich films. These results establish nanopatterned dual‐CD/PVA films as water‐processable, carbon‐dot‐only photonic platforms in which solid‐state emission and light extraction can be jointly engineered through dual‐CD composition and nanoimprinted nanopattern design.
