Advanced Optical Materials最新文献

Reconfigurable and tunable holograms hold significant practical value in the fields of anti-counterfeiting, optical security, and information display due to their ability to reprogram holographic patterns and create variable visual effects. However, current encryption techniques face challenges in achieving rapid encryption/decryption and ensuring consistent methods. In this study, a method for producing a reconfigurable encryption hologram utilizing the deformation and recovery properties of micropillars in response to liquid is demonstrated. Micron-scale micropillars are fabricated using femtosecond laser two-photon polymerization. By exploiting the rapid deformation and recovery capabilities of micropillars with specific pitches and aspect ratios in response to liquids, micropillar structures and holograms are combined to construct reconfigurable holograms. The encrypted pattern information in the reconfigurable holograms is only readable following immersion in alcohol and laser irradiation. The proposed method offers a facile, reversible, reusable, and practical solution for information encryption, with significant potential in anti-counterfeiting and optical security.

In this study, three stable tetradentate Pt(II) complexes are synthesized and characterized, namely, Pt-biPh, Pt-biPh5tBu, and Pt-biPh4tBu, tailored for blue phosphorescent organic light-emitting diodes to realize high-efficiency and narrowband emissions via ligand engineering. Biphenyl (Pt-biPh) or tert-butyl-modified biphenyl (Pt-biPh5tBu and Pt-biPh4tBu) is introduced into the carbene unit of the ligand to control the intermolecular interactions between the Pt(II) phosphors. Pt-biPh, Pt-biPh5tBu, and Pt-biPh4tBu exhibit high photoluminescence quantum yields of 74%, 84%, and 92% with exciton lifetimes of 2.2, 2.3, and 2.5 µs, respectively, demonstrating rapid and efficient light emission. Furthermore, Pt-biPh, Pt-biPh5tBu, and Pt-biPh4tBu show maximum external quantum efficiency (EQE) values of 18.1%, 19.0%, and 21.8%, respectively. Pt-biPh5tBu and Pt-biPh4tBu exhibit narrowband emission with a full width at half maximum of 21 nm owing to the small vibrational emission because of their sterically hindered and bulky ligand structures. Moreover, phosphor-sensitized thermally activated delayed fluorescence devices employing a Pt-biPh4tBu sensitizer achieve a high EQE of 28.6%. In particular, Pt-biPh4tBu performs better than the state-of-the-art phosphor as the sensitizer of the blue phosphor-sensitized thermally activated delayed fluorescence devices in terms of the EQE.

Optical encryption technology attracts considerable attention in the field of information encryption, information storage, and anti-counterfeiting. However, optical encryption based on conventional on/off mode still faces issues such as low scalability, ease of cracking, and poor storage capacity; multi-dimensional and high storage capacity information encryption systems are thus needed. Herein, a programmable information encryption circuit system is demonstrated by constructing a delay light-emitting diode (LED) array using multi-color phosphorescent carbon nanodots (CNDs) with versatile lifetimes. The CNDs show adjustable luminescence wavelength and lifetime from 192 to 1148 ms. The programmable delay luminescent circuit provides an intricate framework for meticulously integrating an LED array, enabling the creation of intricate patterns or alphanumeric codes. These intricate designs are engineered to serve as a component of an encryption system, which can be deciphered and unveiled under a specific delay time range. This study demonstrates the feasibility and superiority of the system as a new type of information anti-counterfeiting encryption technology, providing a new concept for exploring the field of integrated circuit anti-counterfeiting and encryption.

The introduction of liquid crystals into microcavities has garnered considerable attention for their exceptional tunability and high sensitivity to external perturbation factors within their distinct phase states. Here, a novel light source with both wavelength tunability and an exceptionally narrow linewidth is presented. This innovation is realized by strategically manipulating LC molecules, transitioning them from a well-aligned state to a disordered state with increasing temperature. The microcavity is tailored to support bound states in the continuum, a cutting-edge concept in photonic research that allows for light localization with minimal loss. In the pursuit of potential biocompatibility and to reduce cytotoxicity, indium phosphide colloid quantum dots are opted to serve as the emissive carriers within the system. An ultra-narrow linewidth light emission of 0.039 nm is observed, corresponding to a quality factor reaching 16668, along with a tunable range of 1.21 nm and a temperature sensitivity of 33.52 pm K⁻¹. The invention's compact size and tunable character make it an ideal candidate for a variety of potential applications, such as eco-friendly sensors with minimal ecological impact, optical modulators with precise control over light, and adaptable photonic devices that can be integrated with a diverse array of materials and configurations.

Direct Evidence of Ultrafast Energy Delocalization

Energy delocalization is observed in a strongly coupled cavity containing two layers of donor and acceptor molecules, separated by an inert spacer layer of 2 μm thickness. Margherita Maiuri, Tersilla Virgili, and co-workers (see article number 2400821) use two-dimensional electronic spectroscopy, a technique that provides simultaneously high spectral and temporal resolution, to probe the dynamics of the energy flow processes following ultra-fast excitation. Their finding opens new perspectives on remote photo/induced energy transport useful in advanced optoelectronic devices.

Efficient and stable scintillators play a crucial role in X-ray detection applications. To enhance the luminescence efficiency under X-ray excitation, the incorporation of multiple emission centers into scintillators is widely explored. Here, it is found that the cesium copper halide Cs₅Cu₃Cl₆I₂ exhibits dual emission centers, enabling high-performance scintillators with an X-ray light yield of 49000 photon MeV⁻¹ and a low detection limit of 4 nGy s⁻¹. The emissions of Cs₅Cu₃Cl₆I₂ are from intrinsic self-trapped exciton (STE) and Frenkel defect-assisted STE. High-energy X-rays can induce an increased fraction of Frenkel defect-assisted STEs, which can serve as an effective scintillation channel. Furthermore, large-area flexible scintillators with a high resolution of 18 lp mm⁻¹ are developed, making them suitable for X-ray imaging applications. These findings offer promising insights for developing more efficient scintillators.

Polarimetric infrared (IR) detection bolsters IR thermography by leveraging the polarization of light. Optical anisotropy, i.e., birefringence and dichroism, can be leveraged to achieve polarimetric detection. Recently, giant optical anisotropy is discovered in quasi-1D narrow-bandgap hexagonal perovskite sulfides, A_1+xTiS₃, specifically BaTiS₃ and Sr_9/8TiS₃. In these materials, the critical role of atomic-scale structure modulations in the unconventional electrical, optical, and thermal properties raises the broader question of the nature of other materials that belong to this family. To address this issue, for the first time, high-quality single crystals of a largely unexplored member of the A_1+xTiX₃ (X = S, Se) family, BaTiSe₃ are synthesized. Single-crystal X-ray diffraction determined the room-temperature structure with the P31c space group, which is a superstructure of the earlier reported P6₃/mmc structure. The crystal structure of BaTiSe₃ features antiparallel c-axis displacements similar to but of lower symmetry than BaTiS₃, verified by the polarization dependent Raman spectroscopy. Fourier transform infrared (FTIR) spectroscopy is used to characterize the optical anisotropy of BaTiSe₃, whose refractive index along the ordinary (E ⊥ c) and extraordinary (E ‖ c) optical axes is quantitatively determined by combining ellipsometry studies with FTIR. With a giant birefringence Δn ∼ 0.9, BaTiSe₃ emerges as a new candidate for miniaturized birefringent optics for mid-wave infrared to long-wave infrared imaging.

Thin film lithium niobate is one of the most crucial platforms in the next generation of integrated optoelectronics because of its ability to integrate tight optical confinement, low optical loss, and active optical functions. A current challenge in the field of thin film lithium niobate photonics is the development of high-performance photodetectors to achieve multifunctional photonic integrated circuits. This study introduces a high-performance MoTe₂ photodetector integrated on a thin film lithium niobate waveguide. The photodetector achieves the lowest dark current and highest on/off ratio among waveguide-integrated photodetectors on a thin film lithium niobate platform. Due to a slight asymmetry in the behavior of the two electrode contacts of the device, the photodetector also achieves self-driven. At zero bias and a wavelength of 1310 nm, a dark current of ≈20 pA, and an on/off ratio exceeding 10⁵ are achieved. At a bias voltage of 1 V, the measured dark current, responsivity, and on/off ratio are 1.13 nA, 309 mA/W, and 1.8 × 10⁴, respectively. Notably, the device exhibits fast rise and fall times of 9.3 and 13.5 µs, respectively, accompanied by a high detectivity of 2.58 × 10¹¹ W⁻¹.

Pyramid-Shaped Perovskite Single Crystals

Pyramid-shaped perovskite single crystals are constructed with an asymmetrically spatial confinement-induced crystallization method. The crystals exhibit high quality and enhanced absorption capability. A constructed photodetector shows unique advantages, including high performance, flexibility, and insensitivity to the incident photon direction. In this research (see article number 2400329), Gang Ouyang, Wei Hu, Jianfa Zhang, and co-workers provide a promising approach for the development of tandem solar cells and other optoelectronic devices.