ACS Photonics最新文献

Precise signal identification in solar-blind deep-ultraviolet (DUV) detection critically relies on high-performance devices with exceptional spectral selectivity. A novel strategy is proposed to significantly enhance DUV photodetector performance by integrating plasmonic nanohole engineering with ultrashort-period AlN/GaN superlattices for ultranarrow-band detection. Simulations indicate that Al-filled nanoholes with a diameter of 230 nm and a sidewall angle of 60° can yield up to a 31-fold enhancement of the localized electric field at the Al-nanohole sidewall interfaces compared to nanohole structures without Al. Accordingly, metal–semiconductor–metal (MSM) photodetectors incorporating Al-filled hexagonal nanohole arrays within the AlN/GaN superlattice absorption layers were fabricated. The designed three-dimensional architecture, which provides an increased interaction area and effective optical path length, achieves a remarkable peak responsivity of 42.6 mA/W at 238 nm under a 15 V bias. This represents a 4.5-fold improvement over planar reference devices. Furthermore, the devices exhibit ultranarrow spectral selectivity with a full-width at half-maximum (fwhm) of only 19 nm, attributed to the precise spectral alignment between the localized surface plasmon resonance (LSPR) and the superlattice absorption profile. This novel combination of plasmonics and nanohole superlattices offers a promising avenue for high-performance DUV photodetectors in applications requiring highly selective spectral operation.

Two-dimensional (2D) Ruddlesden–Popper perovskite phenylethylammonium lead iodide ((PEA)₂PbI₄) possesses potential photoelectronic properties and is considered to be an ideal material for photodetectors. However, single devices commonly suffer from low responsivity, slow response speed, and narrow detection range, which hinder their applications in imaging, communications, and artificial intelligence (AI). In this work, high-quality 2D (PEA)₂PbI₄ tetragons (TTs) were synthesized via a unique liquid–air interface floating method and integrated with cadmium selenide (CdSe) nanobelts (NBs) to construct a novel hybrid heterojunction photodetector. It confirms that the formation of type-II band alignment at the heterointerface enables efficient interfacial charge transfer. Notably, the (PEA)₂PbI₄/CdSe heterojunction hybrid device exhibits exceptional performance under 450 and 682 nm monochromatic illumination: extremely high responsivity (R) (2.80 × 10³ and 6.39 × 10³ A/W), excellent detectivity (D*) (4.09 × 10¹³ and 9.32 × 10¹³ Jones), large external quantum efficiency (EQE) (7.74 × 10⁵% and 1.16 × 10⁶%), and remarkable I_on/I_off ratio (3.60 × 10⁵ and 8.66 × 10⁵), as well as fast response speeds (rise/decay time: 108/265 μs and 86/196 μs). Furthermore, the hybrid device overcomes the intrinsic bandgap limitation of (PEA)₂PbI₄, extending its photoresponse to cover nearly the entire visible spectrum and demonstrating reliable imaging capability. This study provides an innovative strategy for developing high-performance photodetectors with significant practical application potential.

Perovskite light-emitting diodes have emerged as promising candidates for next-generation lighting and display technologies owing to their superior efficiency and high color purity. However, the perovskite active layers are highly sensitive to moisture and oxygen in ambient air, necessitating fabrication under protective atmospheres, which would increase production costs and limit industrial scalability. Moreover, the use of toxic antisolvents poses additional environmental concerns. Here, we report air-processable reduced-dimensional perovskites enabled by a dual passivation strategy to reduce the defect density and improve the film quality. Specifically, ammonium trifluoromethanesulfonate was incorporated into the perovskite precursor solution, while tris(4-fluorophenyl)phosphine oxide was introduced via an eco-friendly antisolvent (ethyl acetate). These passivating agents effectively coordinate with the perovskite framework, suppressing defect formation. The resulting devices achieved a maximum external quantum efficiency of 13.9% and enhanced operating stability and economic efficiency, thereby bringing an important step toward the commercialization of perovskite light-emitting diodes in optoelectronic applications.

The efficacy of photodynamic therapy (PDT) is strongly influenced by the biodistribution of the photosensitizer and the local generation of ¹O₂ within tumor tissue. However, real-time in vivo monitoring of these critical parameters for clinically approved photosensitizers remain a major challenge in translational photodynamic research. We report a novel portable bifurcated fiber-coupled time-resolved singlet oxygen luminescence detection instrument combining an integrating pulsed 690 nm diode laser system. Using this instrument, ¹O₂ signal is estimated corresponding to the uptake kinetics of the clinical photosensitizer benzoporphyrin derivative (BPD) in tumor-bearing mice up to 3 h post injection along with pre- and post-PDT ¹O₂ luminescence were measured in the same mice. The measured ¹O₂ counts correlate with the increase in BPD accumulation in the tumor region from 15 min to 2 h post injection and then remain constant in the 2–3 h measurement period. A strong positive correlation was observed between local BPD uptake and singlet oxygen signal. The estimated lifetime of ¹O₂ in vivo was 0.25–0.35 μs. The TSOLD system provided consistent, noninvasive readouts of ¹O₂ generation in real time with minimal background interference. Control experiments using BPD-free conditions confirmed the specificity of the detected signal. This study demonstrates a novel, noninvasive optical approach for simultaneous murine in vivo quantification of photosensitizer uptake and singlet oxygen production during PDT. This portable TSOLD instrument enables dynamic monitoring of therapeutic conditions in preclinical cancer models and has potential for future adaptation to clinical settings, supporting more precise and personalized PDT planning and dosimetry.

We report on the monolithic, two-step epitaxial growth of site-controlled InGaAs quantum dots via the buried-stressor method with local quantum dot density variation. As a result of high fabrication accuracy, we achieve low lateral displacements of the individual buried-stressor apertures of ${17}_{-17}^{+19}\mathrm{nm}$ from the mesa centers. We provide extensive microphotoluminescence and cathodoluminescence characterization of the site-controlled quantum dots and give theoretical calculations explaining the effect of the stressor aperture on the quantum dot emission properties, positioning, and density. We show reproducibility of the nucleation process for apertures of the same size and achieve precisely positioned, low- and high-density quantum dot nucleation within one active-layer growth step. The results presented in this work demonstrate the significant potential of the buried-stressor concept in fabricating single photonic chips, simultaneously combining single-photon sources and microlasers featuring different local densities of the site-controlled quantum dots, paving the way for highly functional source modules with applications in photonic quantum technology.

Micro light-emitting diodes (micro-LEDs) based on gallium nitride (GaN) semiconductors are considered revolutionary technology for microdisplays and virtual displays. However, micro-LEDs still suffer from severe efficiency droop caused by sidewall damage during pixelation when the pixel sizes are reduced to about 10 μm or less, hindering their prospects in the fields of commercial applications. Here, we proposed a novel mesa structure design with ion implantation passivated side edges for fabricating enhanced-performance micro-LED arrays. High-resistivity insulation areas in the P-GaN layer induced by tailored F^– ion implantation surround active light-emitting areas to keep the injection current path far away from sidewall defects. It concludes that, by the additional tailored F^– ion implantation process, the photoelectric properties are significantly improved, including leakage current, light output power, luminous efficiency, and color purity for the as-fabricated ultrasmall InGaN-based blue micro-LEDs with pixel sizes of 10, 8, and 6 μm. Additionally, the proposed novel pixelation process conducted by ion implantation plus selective etching can also conduce to enhancing light extraction efficiency and reducing optical crosstalk, in contrast to the as-reported planar pixelation process. This work provides an effective method to improve the performance of ultrasmall micro-LED arrays through fabricating fluorine ion implantation passivated mesas.

Structured illumination microscopy (SIM) offers rapid, long-term super-resolution imaging, but its performance is fundamentally constrained by sample-induced aberrations that vary across large fields of view and imaging depths. Here, we present Fourier Ptychography-assisted SIM (FP-SIM), an adaptive optics-assisted, large-field SIM that enables in situ correction of spatially variant aberrations via Fourier ptychography (FP). By leveraging FP’s quantitative phase retrieval capability, FP-SIM reconstructs pupil phase maps directly from coherent, label-free measurements and applies them to fluorescence SIM reconstruction, enabling accurate aberration correction without relying on fluorescent guide signals. The approach performs guide-star-free, tile-by-tile wavefront sensing using coherent measurements, achieving high-resolution fluorescence imaging across extended fields of view. Experimental validation on various samples demonstrates significant improvements in resolution, contrast, and artifact suppression over state-of-the-art tiled and notch-filtered SIM methods. In addition to providing a complementary label-free imaging modality, FP-SIM offers a versatile and flexible solution for large-scale, depth-resolved, aberration-resilient fluorescence microscopy with high imaging fidelity.

Metasurfaces composed of subwavelength meta-atoms are promising platforms for next-generation optical technologies, including metalenses, holography, AR/VR displays, and biomedical imaging. Among these devices, metaholograms offer ultrathin form factors and high-resolution image reconstruction, but their practical implementation remains limited by material constraints and fabrication complexity. Although passive dielectric materials such as TiO₂, Si₃N₄, and polymers provide high optical performance, the lack of intrinsic electro-optic tunability hinders progress toward dynamically reconfigurable metasurfaces, and fabrication methods such as electron-beam lithography remain costly and low throughput. In this work, we demonstrate a scalable and cost-effective route for fabricating high-performance metaholograms using nanoimprint lithography and a newly developed BaTiO₃ nanoparticle-embedded resin (BTO PER). The BTO PER exhibits a high refractive index, low optical loss in the visible spectrum, and excellent nanoformability compatible with direct imprinting. Dispersing BTO nanoparticles into a thermally curable polymer matrix enables high-fidelity nanopattern transfer without vacuum-based processing while preserving the intrinsic ferroelectric characteristics of BTO after imprinting. The fabricated metaholograms achieve an optical efficiency of 38.6% at 450 nm, consistent with simulation, confirming efficient phase modulation by the engineered nanostructures. Furthermore, the preserved ferroelectric behavior suggests strong potential for future electrically tunable or reconfigurable metasurfaces, establishing a manufacturable and functionally versatile platform for visible-wavelength metaholograms and adaptive photonic devices.

A high-performance near-infrared (NIR, λ > 1400 nm) photodetector is developed based on large-sized lead sulfide colloidal quantum dots (PbS CQDs) surface-engineered with the ionic liquid ligand 1-ethyl-3-methylimidazolium thiocyanate (EMIMSCN). Through the synergistic action of thiocyanate (SCN^–) anions and EMIM⁺ cations, a robust dual-facet passivation structure is formed on both the polar (111) and nonpolar (100) facets. The SCN^– anion strongly coordinates with under-coordinated Pb²⁺ sites, while the EMIM⁺ cation adopts a face-to-face π-conjugated orientation on the (100) surface, leading to effective suppression of surface trap states and halide migration. This cooperative passivation mechanism significantly improves film quality, reduces defect density, and enhances carrier transport. As a result, the optimized devices exhibited a dark current density as low as 4 μA cm^–2 at −1 V, a responsivity of 0.75 A W^–1, and a specific detectivity of 5.2 × 10¹¹ Jones at 1490 nm, outperforming conventional halide-passivated CQD devices. Furthermore, monolithic NIR-to-visible upconversion photodetectors are successfully demonstrated, achieving a record photon-to-photon conversion efficiency of 3.15%. This ion-pair ligand strategy provides a versatile and stable passivation route for large-sized PbS CQDs, enabling next-generation low-noise and high-stability NIR optoelectronic devices.

Nonlocal metasurfaces have garnered significant interest for applications that require customized and enhanced light–matter interactions in a flat form factor. These metasurfaces are distinctive for their ability to systematically control some of the fundamental properties of optical resonances by manipulating the in-plane symmetry of the lattice. Recent theoretical works have suggested that engineering the symmetry of a metasurface not just within the plane of the metasurface but also in the vertical or out-of-plane direction enables improved control of additional fundamental properties, especially chirality. However, standard nanofabrication processes cannot readily support elaborate vertical symmetry breaking such as nanostructure heights or slopes that deliberately vary across the footprint of a metasurface. In this work, we experimentally demonstrate a scalable method to lithographically define the vertical symmetry of nonlocal metasurfaces by selectively eroding the etch mask during the etch process. Moreover, as the etch mask erosion rates depend on the in-plane size of individual nanostructures, we introduce and experimentally demonstrate a compatible design framework that enables versatile control over the properties of optical resonances. The results hold promise for chiral nonlocal metasurfaces with highly customized behavior.