Advanced Optical Materials最新文献

Terahertz waves can be widely used for short-range communication in complex indoor environments and non-destructive object detection applications. Metasurfaces are widely used in terahertz sensing and communication devices because they can modulate terahertz waves in multiple dimensions. Metamaterial robot brain can utilize metasurfaces' powerful direct modulation ability to achieve sensing and communication functions. The metasurface devices realized based on Dynamic Heterogeneous Redundancy (DHR) architecture can improve the confidentiality and security of terahertz wave wireless communication. While the intrinsic ohmic loss and quality factor of usual metallic metamaterials are usually low, the concept of bound states in the continuum (BIC) has been proposed for stronger terahertz-matter interactions. Among them, high-order BICs are of interest because of their strong robustness to structural defects. Therefore, an aluminium-graphene hybrid metasurface with high-order BIC is proposed. We have the principle of excitation of high-order BICs is investigated and creatively proposed with high robustness realized using the magnetical EIT effect. The robustness of the high-order BIC is also utilized to design security hardware based on DHR architecture. The designed secure hardware can satisfy the demand for an intelligent robotic brain to the internal terahertz wave confidential wireless communication.

Anti-counterfeiting and encryption are key technologies for information transmission in modern society. However, most optical materials offer only a single fixed response mode, limiting their security level in advanced anti-counterfeiting applications. Exploring efficient and tunable long persistent luminescent (LPL) phosphors is urgently demanded and highly meaningful. In this work, a dual-site occupancy strategy is innovatively reported via Li⁺ doped NaGaO₂: Cu²⁺ (NGO: Cu²⁺/Li⁺) phosphors for enhancing LPL properties. To be specific, Cu²⁺ initially occupies both Na and Ga sites in NaGaO₂, producing orange–yellow LPL at 585 nm and near-infrared (NIR) emission at 712 nm, respectively. Furthermore, the introduction of Li⁺ will occupy the Na⁺ sites, attenuating the NIR emission and increasing the defect density of the oxygen-deficient states, which results in enhanced LPL intensity and prolonged afterglow time. Significantly, the obtained NGO:Cu²⁺/Li⁺ exhibits multi-emission modes with dynamic change of LPL time (10–20 min). More importantly, the NGO: Cu²⁺/Li⁺ has great potential applications in multi-level information storage and encryption.

Triplet–triplet annihilation (TTA), or triplet fusion, is a biexcitonic process in which two triplet-excited molecules can combine their energy to promote one into an excited singlet state. To alleviate the dependence of the TTA rate and yield on triplet diffusion in both solid and solution environments, intramolecular TTA (intra-TTA) has been recently proposed in conjugated molecular systems able to hold multiple triplet excitons simultaneously. Developing from the previous demonstration of TTA performance enhancement in sensitized upconversion solutions, here similar improvements in triplet harvesting in solid-state films are reported under electrical excitation in organic light emitting diodes (OLEDs). At low dye concentration and low current densities, the intra-TTA active OLED shows a +40% improved external quantum efficiency with respect to the reference device, and a TTA spin-statistical factor f ^4DPA of 0.4, close to that determined in fluid solution for the individual chromophore (0.45). These results therefore indicate the utility of this molecular design strategy across a wider range of TTA applications, and with particular utility in the further development of low-power TTA-enhanced OLEDs.

Carbon quantum dots (CQDs) have emerged as promising materials for optoelectronic applications and have garnered much interest as potential competitors to conventional inorganic or hybrid semiconductor quantum dots because of carbon's intrinsic merits of high stability, low cost, and environment-friendliness. The ability of easy formulation of functional ink of CQDs is necessary for the development of industrial-scale, reliable, inexpensive printing/coating processes, for its full exploitation in the ever-growing class of applications in sensors, optoelectronics, and energy storage and conversion. Here a facile one-step room-temperature synthesis of printable, fluorescent CQD ink is demonstrated. The as-synthesized fluorescent CQD ink is used for invisible fingerprint stamps, printing of micro-patterns, and soft lithographic patterning with a resolution down to 1.5 µm. This functional CQD ink is also used to fabricate a high-performance CQD-ZnO heterojunction ultraviolet (UV) photodetector with a photo-responsivity of 3.85 A W⁻¹, detectivity of 6.78 × 10¹⁰ Jones, and an external quantum efficiency (EQE) of 15.3%. The enhanced device performance can be attributed to CQD's high photocurrent generation efficiency and rational combination of the asymmetric electrode materials. This work enables a high-temperature stable CQD fluorescent ink synthesis method to fulfill the processing requirements of printing and soft lithographic patterning for visual encryption and optoelectronics.

Efficient Molecular Array Control and Vapochromic Behavior Changes

The study by Kyung-Ryang Wee and co-workers in article number 2401305 introduces a strategy to control molecular arrays by modifying the shapes of donor–acceptor–donor building blocks via positional isomerism. Molecular shape variations lead to distinct arrays, affecting intermolecular interactions and void volumes, influencing the macrostructure and resulting in different vapochromic behaviors.

Pulsed-Laser Deposition of Ge-Doped BiTe Nanofilms for Photodetection

Pulsed-laser deposition is developed for the large-area synthesis of Ge-doped BiTe nanofilms, which are successfully exploited for room-temperature high-speed long-wave infrared photodetection and optical communications. For more information on these achievements, see article number 2401937 by Jiandong Yao, Huanjun Chen, and co-workers.

Persistent luminescence (PersL) has attracted considerable attention in the last two decades for its potential applications in the fields of emergency indicators, energy-saving lighting, biomedical imaging, and dynamic anti-counterfeiting. However, the wavelengths of PersL reported so far usually fall into the visible and near-infrared range. The preparation of advanced optical materials bearing UV PersL remains elusive. Here the PersL characteristic of CaF₂:Gd³⁺ is systematically studied. After exposure to X-ray radiation, CaF₂:Gd³⁺ continues to emit UV­-B (UVB) PersL peaking at 313 nm, corresponding to the ⁶P_7/2 → ⁸S_7/2 transition of Gd³⁺. By virtue of X-ray photoelectron spectroscopy measurements, the valence variation model is excluded to explain the UVB PersL of CaF₂:Gd³⁺. Finally, it is demonstrated that such UVB PersL of CaF₂:Gd³⁺ can be used for static labeling and dynamic tracing.

Optical neural networks (ONNs) have shown great promise in overcoming the speed and efficiency bottlenecks of artificial neural networks. However, the absence of high-speed, energy-efficient nonlinear activators significantly impedes the advancement of ONNs and their extension to ultrafast application scenarios like real-time intelligent signal processing. In this work, a novel silicon/graphene ultrafast all-optical nonlinear activator, leveraging the hybrid integration of silicon slot waveguides, plasmonic slot waveguides, and monolayer graphene is demonstrated. Exploiting the exceptional picosecond-scale photogenerated carrier relaxation time of graphene, the response time of the activator is markedly reduced to ≈93.6 ps, establishing all-optical activator as the fastest known in silicon photonics to knowledge. Moreover, the all-optical nonlinear activator holds a low threshold power of 5.49 mW and a corresponding power consumption per activation of 0.51 pJ. Its feasibility and capability for use in ONNs, manifesting performance comparable with commonly used activation functions are experimentally confirmed. This breakthrough in speed and energy efficiency of all-optical nonlinear activators opens the door to significant improvements in the performance and applicability of ONNs.

High-resolution infrared (IR) imaging technology holds substantial significance across diverse fields including biomedical imaging, environmental surveillance, and IR digital cameras. Current IR detectors used in commercial applications are based on ultra-high vacuum-processed traditional inorganic semiconductors like silicon or III-V compounds (e.g., Si, Ge, and InGaAs). However, the rapid advancements in applications such as autonomous vehicles, virtual reality, and point-of-care healthcare are driving an escalating need for innovative imaging technologies. This review aims to bridge the gap by exploring solution-processed semiconductor photodetectors (PDs), which offer distinct advantages including cost-effectiveness, tunable spectral response, and potential for multiple-exciton generation. These characteristics make them particularly suitable for optical communication, IR imaging, and biological monitoring applications. This review provides comprehensive insights into the research trends pertaining to solution-processed IR detectors and imagers based on colloidal quantum dots, perovskites, organic compounds, and 2D materials. The review commences with the current market worth of image sensors, the fundamental principles of single-pixel and multipixel array IR imagers, and key parameters used to assess IR detector performance. In essence, the review concludes with a summary of recent advancements and future prospects for next-generation IR PD devices and their potential application as an IR imager.