Advanced Optical Materials最新文献

Diversity and security for information transmission urgently require the rapid developments in both steganographic media and anti-counterfeiting technology. Plasmonic holography mediated with nano-Au or nano-Ag has attracted much attention in enhanced data security. However, holographic systems are usually manipulated in the familiar optical dimension, which greatly increases the risk of information being deciphered. Herein, an Ag/Au bimetal stacking steganography is proposed that combines optical holography and chemical Ostwald ripening. The nano-Au on a TaO_x substrate constructs addressing-key, which is hidden by coating a continuous Ag thin film. The confused ciphertext and computer-generated holograms (CGH) are successively written in the stacked array by nanosecond pulsed lasers. Benefiting from the difference of the ripening reaction rate of the silver layer in halide solutions between Ag/Au/TaO_x and Ag/TaO_x regions, the addressing-key information of nano-Au can be accurately extracted, providing correct reading position coordinates for hologram display of Ag/Au/TaO_x regions. This work puts a bright way to high-security information protection.

Lead halide perovskite nanocrystals (NCs) are promising materials for next-generation optoelectronic devices due to their exceptional optical properties. However, poor long-term stability remains a major challenge. In this study, formamidium lead bromide (FAPbBr₃) NCs are embedded in a mesoporous silica matrix to enhance stability and explore exciton transport mechanisms. These NCs display a narrow photoluminescence (PL) linewidth of 25 meV at 7 K. The absence of surface ligands leads to reduced interparticle spacing, favoring non-radiative Förster resonance energy transfer (FRET) as the dominant exciton transport mechanism. Using time-resolved and spectrally-resolved PL spectroscopy at cryogenic temperatures, it is observed significant spectral redistribution over time, indicating energy transfer from higher-energy to lower-energy NCs. To quantitatively interpret these dynamics, a theoretical model based on a 2D array of coupled NCs, incorporating Förster's theory to simulate exciton diffusion is employed. This model successfully reproduces the experimentally observed PL decay behavior, confirming FRET-mediated exciton transport with an upper-limit efficiency close to 100% and a transfer rate of 105 ns⁻¹. These findings offer key insights into energy transfer processes in ligand-free perovskite NC systems and underscore the potential of mesoporous silica matrices for improving stability and enabling control over excitonic interactions in perovskite-based optoelectronic applications.

Organic photodetectors (OPDs) based on co-evaporated bulk heterojunctions (BHJs) have demonstrated their potential for industrially relevant fabrication of high-efficiency devices. However, acceptor materials choice is still dominated by fullerenes, which show sub-optimal performance due to deep trap states originating from unfavorable BHJ morphology. Herein, the non-fullerene acceptor Cl₆-SubPc is used to replace C₆₀ in 2-((8-methyl-8H-thieno[2,3-b]indol-2-yl)methylene)−1H-cyclopenta[b]naphtha-lene-1,3(2H)-dione (MPTA):C₆₀ BHJs. Through active layer thickness tuning, the effective Cl₆-SubPc intercalation into MPTA domains is achieved for a highly intermixed BHJ morphology. This results in a high yield of interfacial charge-transfer states, which are readily quenched under electric field for efficient OPD photoresponse. In comparison to C₆₀-based devices, Cl₆-SubPc suppresses the residual MPTA aggregation and the adduct generation with MPTA, preventing deep-trap state formation. As such, non-fullerene acceptor-based OPDs are highly promising for trap-free photodetection, enabling superior performances under low-light illumination.

Terahertz (THz) hyperspectral imaging (HSI) is a promising non-invasive analytical technique that enables the simultaneous capture of spatial and spectral information. However, traditional lenses used in THz HSI systems are bulky and suffer from severe chromatic and spherical aberrations, which result in large dispersion and a limited field of view (FOV). Furthermore, the diffraction limit also restricts the corresponding spatial-spectral resolution. Therefore, lenses are urgently needed to achieve high spatial-spectral resolution THz HSI with a wide field of view. In this study, an equivalence is established between the precise refractive index distribution required for a metalens with a wide FOV and its thickness profile, greatly simplifying the fabrication process. The associated THz microlenses enable high spatial-spectral resolution HSI from 0.2 to 0.7 THz. The finest spatial and spectral resolutions are ≈0.6λ and 0.1 THz, respectively, with a numerical aperture (NA) of 0.555 and a large FOV of 60°. The associated sample is fabricated using 3D printing technology and low-dispersion materials. The approach provides practical and cost-effective means to achieve achromatic super-resolution HSI, underscoring the significant importance of THz HSI in various domains, including bioimaging, biosensing, and non-destructive testing.

Efficient guiding and manipulation of photons at the nanoscale is essential for optical communication and computing. Recent studies have demonstrated that atomically thin 2D semiconductors can function as waveguides even at atomic-scale thickness, also enabling optical modulation. However, electrical control over guided modes in these atomically thin 2D semiconductors remains largely unexplored. In this report, electrical modulation of guided exciton-polariton modes within a van der Waals heterostructure composed of an atomically thin tungsten disulfide (WS₂) monolayer integrated with hexagonal boron nitride (hBN) is demonstrated. Due to the electrostatic tunability of excitons in monolayer WS₂, the guided polariton modes in the WS₂/hBN heterostructure can be electrically modulated. The polariton dispersions in this heterostructure are directly observed under varying gate voltage by using the near-field coupling technique. Remarkably, the polariton dispersion can be switched off by applying an electrostatic gate voltage of 30 V to optically transparent indium tin oxide (ITO) electrodes. It is believed that this work provides a promising platform for nanoscale polaritonic devices and their integration into on-chip applications.

Multifunctional metasurfaces hold great promise for next-generation communication systems, enabling spectral efficiency, dynamic adaptability, and hardware scalability for performing multiple wavefront manipulation tasks. However, traditional designs often neglect critical near-field interactions, leading to performance degradation in complex aperiodic configurations. In this work, an AI-driven design model is presented for a single-layer, passive, transmission-mode multifunctional metasurface capable of projecting different holographic patterns at 86 GHz (W-band) through spatial multiplexing of the input excitation. The approach integrates a diffractive neural network with an optimization algorithm and a phase-smoothing regularization scheme to mitigate mutual coupling between unit cells. The proposed model refines the phase profile to balance target performance and physical constraints, enhancing the validity of the local periodicity approximation. The experimental results closely match the simulations, validating the proposed method. This work demonstrates that an AI-driven model, enhanced by physical regularization, offers a scalable and efficient path toward high-performance multifunctional metasurfaces, enabling dynamic-like functionalities without active components—crucial for next-generation wireless communication systems.

Electron tomography (ET) is an outstanding technique to access information about nanoparticles whose properties are critically dependent on their 3D shape and structure. A particularly relevant application of ET concerns plasmonic chiral nanoparticles, which exhibit strong correlation between optical activity and asymmetric morphology. Thus, it is crucial to go beyond qualitative visual inspection of ET reconstructions and extract quantitative shape or chirality descriptors. However, the time-consuming nature of conventional ET, where a series of 2D projection images is used for one 3D reconstruction, makes it challenging to collect statistically representative data. A recently proposed semi-automated approach for the acquisition of the required tilt series can reduce the data collection time from typically ≈ 45 minutes–1 hour to less than 10 minutes. What remains unclear is how this method influences the quality of the reconstruction and the accuracy of the samples’ quantitative descriptors. Here, two sets of chiral gold nanoparticles with wrinkled or twisted morphological chirality are used. It is demonstrated that the fast tilt series acquisitions yield results that are consistent with conventional ET, provided a standardized data processing protocol is used. Finally, a practical example of how fast ET can be used to obtain more statistically relevant measurements is presented.

PbSe exhibits significant potential for photodetection applications. Chemical doping is a well-established method for modulating the band structure and carrier mobility of materials. In this study, an innovative strategy is reported for the first time that combines in situ oxidation with co-sputtering deposition to fabricate and simultaneously oxidize tin-doped PbSe films. The sensitized PbSnSe alloy films exhibit a narrow bandgap, high carrier mobility, excellent optical response characteristics, and broad detection capabilities (405–5000 nm). The maximum responsivity achieved by this detector is 3 A W⁻¹ with a specific detectivity of 1.8 × 10¹¹ Jones. Furthermore, it demonstrates good optical response uniformity along with consistent mid-infrared imaging capability at room temperature. Additionally, the detector showcases an ultrafast response speed exceeding 1 µs @808 nm and maintains a high switching rate greater than 10⁵(I_on/I_off = 10⁵). This research provides novel insights into optimizing the performance of PbSe-based infrared detection materials while highlighting their critical reference value in balancing preparation methods with material performance. Consequently, this work offers theoretical support as well as experimental foundations for designing high-performance infrared detectors and establishes a comprehensive framework for developing highly stable infrared optoelectronic materials.

Excitons in biased bilayer graphene are electrically tunable optical excitations residing in the mid-infrared (MIR) spectral range, where intrinsic optical transitions are typically scarce. Such a tunable material system with an excitonic response offers a rare platform for exploring light–matter interactions and optical hybridization of quasiparticles residing in the long wavelength spectrum. In this work, it is demonstrated that when the bilayer is encapsulated in hexagonal-boron-nitride (hBN)—a material supporting optical phonons and hyperbolic-phonon-polaritons (HPhPs) in the MIR—the excitons can be tuned into resonance with the HPhP modes. It is found that the overlap in energy and momentum of the two MIR quasi-particles facilitate the formation of multiple strongly coupled hybridized exciton-HPhP states. Using an electromagnetic transmission line model, the dispersion relations of the hybridized states are derived and showed that they are highly affected and can be manipulated by the symmetry of the system, determining the hybridization selection rules. These results establish a general tunable MIR platform for engineering strongly coupled quasiparticle states in biased graphene systems, opening new directions for studying and controlling light–matter interactions in the long-wavelength regime.

Counterfeiting poses a severe global threat to economic security and public safety, driving an urgent demand for advanced anti-counterfeiting technologies that are difficult to replicate. Lead-free halide perovskites (LFHPs) have emerged as a promising platform, offering eco-friendly composition, structural versatility, and highly tunable luminescence. This Review systematically summarizes recent advancements in LFHP-based anti-counterfeiting strategies, categorized into single-level, dual-level, and multi-level systems. Unlike conventional approaches, LFHPs enable dynamic encryption through excitation-dependent emission, up/down-conversion, near-infrared luminescence, long-persistent afterglow, and stimuli-responsive behaviors (e.g., hydrochromism, thermochromism, and mechanochromism). Multi-level strategies are particularly highlighted that integrate time-resolved and stimulus-activated features, significantly enhancing security and information capacity. Despite rapid progress, challenges remain in scalability, environmental stability, and cost-effective fabrication. This Review not only elucidates the structure–property relationships and underlying mechanisms of LFHPs but also provides a forward-looking perspective on their practical application potential. Material design principles, performance limitations, and future directions are outlined, such as the development of multi-modal responsive systems and integration with scalable printing technologies. By addressing these aspects, this Review aims to guide the rational design of next-generation, high-security anti-counterfeiting materials and promote their adoption in next-generation security systems.