NeoPhotonics (United States)

Cubic boron nitride (c-BN) and hexagonal boron nitride (h-BN) are known for their transparency and high 10B density, which provides a large thermal-neutron cross-section, yet their potential for space neutron shielding has not been explored. The fabrication of transparent c-BN films remains challenging, and the chemical vapor deposition growth of h-BN beyond 70nm, or with precise thickness control and high uniformity, has not been reported except by our group. Here, we present a space window design integrating an h-BN-based neutron shielding layer with advanced ceramic bulletproof layers and a γ-ray shielding layer. By incorporating C and O into h-BN, sp2-sp3 hybridized BN (HBN) reduces the refractive index mismatch with the SiO2 substrate, achieving 90.9% transmission at 550nm at 11.9µm thickness and enabling stable, transparent growth up to 79.2µm with minimized thermal expansion mismatch. The optically optimized HBN (B0.39N0.39C0.06O0.16) shows reduced boron content, but the enriched formation of 63.4% c-BN, with its higher boron density, compensates for this loss. The resultant density is 3.01g cm-3, evaluated from neutron-shielding probability, and HBN achieves the same neutron-shielding efficiency as h-BN at 3% reduced thickness.

ABSTRACT Solution processing provides a scalable route to assemble 2D building blocks into large‐area films with low intersheet resistance, enabling scalable device integration. However, chalcogen vacancies introduced during processing often cause unintentional doping, and passivation strategies relying on strong reagents and controlled atmospheres increase process complexity. Here, rather than eliminating vacancies typically regarded as detrimental, we exploit vacancy‐localized states in solution‐processed MoS 2 as essential defects to realize retinomorphic device arrays in which sensing and memory are co‐localized within a two‐terminal device. Trapping of photoexcited carriers at these vacancy‐localized states enhances photogating and induces persistent photoconductivity, writing retentive conductance states without the need for additional trapping layers, floating gates, or complex heterostructures. The stored state is reversible upon oxygen exposure, which promotes de‐trapping and restores the dark baseline. Additionally, wavelength‐selective conductance modulation enables multilevel accumulation of color‐encoded weights for RGB differentiation. Increasing optical pulse number progressively enlarges inter‐color conductance contrast; when integrated with a convolutional neural network framework, the encoded states enable color recognition accuracy up to 94%. By exploiting a defect landscape inherent to solution‐processed 2D films, this work establishes a scalable materials platform that simultaneously integrates sensing and memory at the pixel level while reducing processing complexity.

Phenylethylammonium (PEA) organic spacer-based quasi-two-dimensional (Q-2D) perovskites have garnered considerable attention due to their tunable optoelectronic properties and high environmental stability. However, the response speed and responsivity of PEA-based Q-2D perovskite photodiodes (Q-2D PPDs) remain limited by inadequate carrier transport and collection. Herein, we propose a simple yet effective crystal orientation control strategy to overcome these limitations. Compositional engineering of the photoactive layer is employed to suppress defect formation and promote out-of-plane crystal orientation, which facilitates carrier transport in vertical n–i–p photodiodes. Concurrently, the optimized surface morphology of the Q-2D perovskite film enables the implementation of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) as a hole transport layer to enhance hole extraction, block interfacial electron injection, and reduce dark leakage current. Our self-powered Q-2D PPDs, featuring a device architecture of ITO/SnO2/(4F-PEA)2(MA)3Pb4I11Cl2/PTAA/Au, exhibit ultrafast response times of 2.5 μs/1.9 μs (rise/fall), a responsivity of 0.25 A/W, and a detectivity of 3.4 × 1012 Jones at 550 nm. Notably, the unencapsulated detectors show excellent operational stability for over 180 days under ambient conditions. The remarkable detection performance of the Q-2D PPDs was further demonstrated in image sensing and indirect X-ray detection, showcasing their potential for versatile optoelectronic applications.

A new picosecond light source for ultra-sensitive SRS microscopy allow imaging in the CH- and fingerprint region as well as of Raman labels. Its fast tuning of about one second enables easy multispectral SRS imaging.

Group IV color centers in diamond are promising single-photon emitters for quantum information processing and networking. Among them, the tin-vacancy (SnV) center stands out due to its long spin coherence times at cryogenic temperatures above 1 K. While SnV centers have been realized using various fabrication routes, their in situ formation via microwave plasma-enhanced chemical vapor deposition (MW PE CVD) remains relatively unexplored. In this study, SnV centers, identified by a zero-phonon line (ZPL) near 620 nm, were synthesized in nanocrystalline diamond and free-standing microcrystalline diamond using tin oxide (SnO2) as a dopant source at substrate temperatures of 750°C and 850°C. Photoluminescence measurements reveal that lowering the substrate temperature enhances both the ZPL intensity and spatial uniformity of SnV centers. These results highlight substrate temperature as a key parameter for controlling SnV incorporation during MW PE CVD growth and provide insights into optimizing fabrication strategies for diamond-based quantum technologies.

The manipulation of photoluminescence (PL) in two-dimensional (2D) materials presents a promising approach for the development of compact and tunable nanoscale light sources. Although monolayer transition metal dichalcogenides (TMDCs) exhibit strong excitonic emission owing to their direct bandgap, multilayer TMDCs generally experience reduced PL efficiency due to their indirect band structure. Here, we demonstrate that nanostructured WS2 deposited on an Ag film exhibits markedly enhanced indirect PL emission, facilitated by metal film-assisted near-field enhancement and exciton-resonant excitation. Through systematic comparison of WS2 nanoparticles on Ag and indium tin oxide (ITO) film under varying excitation wavelengths and powers, we show that the Ag substrate enhances PL intensity via metal film-induced field concentration, which is about 27 times stronger than that on the ITO film with the same excitation condition. Numerical simulations corroborate that the observed enhancement results from the enhancement effects of electric field localization and exciton-resonant absorption. Moreover, high-energy excitation induces additional PL peaks, which are attributed to hot carrier relaxation and direct transition phenomena. These findings provide fundamental insights into exciton dynamics within multilayer TMDC nanostructures and propose a scalable strategy for engineering their optical responses through hybrid platforms, thereby establishing a foundation for future applications in nonlinear optics, quantum photonics, and integrated 2D material-based optoelectronic devices.

Ultrasensitive photodetectors with high responsivity, rapid response speed, and low dark current are in urgent demand for a wide range of applications. The coupling between plasmonic metals and heterojunctions can enhance light absorption capabilities and facilitate hot electrons injection. However, recent research on plasmonic heterojunction devices has primarily focused on enhancing the local electromagnetic field, while the practical use of hot electrons remains limited. This is due to the formation of defects when metal nanoparticles (NPs) are integrated onto the surface of heterojunctions. Energetic hot electrons and photogenerated carriers are trapped by defect states, resulting in prolonged carrier lifetimes. The excited-state carriers cannot be effectively utilized, which reduces the photoelectric conversion efficiency of the devices. In this study, we propose a Cu@CuO core–shell plasmonic structure designed for ultrasensitive photodetection. The presence of the CuO layer effectively reduces defects and establishes a Type-II band alignment for the device, thereby enhancing hot electrons injection efficiency and charge transfer. The MoS2/Cu@CuO photodetector exhibits a high responsivity (633 A/W) without sacrificing the response speed (28 ns). The core–shell architecture of metal NPs provides a viable strategy for further development of ultrasensitive photodetectors utilizing hot electrons injection.

Photocatalytic methanol dehydration to dimethyl ether (DME) offers a sustainable alternative to energy-intensive thermocatalysis, yet its practical application remains constrained by low efficiency. Herein, we designed Ni-doped plasmonic W18O49 nanowires that synergistically integrates low-coordinated W and Ni dual active sites with surface plasmon resonance for enhanced photocatalytic performance. The synergistic effect of W and Ni dual sites is amplified by plasmonic electron oscillations to facilitate the C-O bond cleavage and C-O-C coupling, driving efficient methanol-to-DME conversion. The optimized Ni0.66-W18O49 achieves a DME yield of 133.7 ± 3.3 mmol g-1 h-1 with 98.7% selectivity under 400 mW cm-2 illumination. The versatility of the catalyst is demonstrated through C2+ alcohol dehydration, achieving 40-80% rate enhancements and a recorded isobutylene yield of 3.7 mol g-1 h-1. This study highlights the huge potential of rationally engineered plasmonic semiconductors in solar-driven chemical synthesis, particularly for C-O bond activation and coupling reactions.