Advanced Optical Materials最新文献

Chromatic aberration has been the main showstopper for metalenses when it comes to imaging applications with broadband sources such as ambient light. In wide field-of-view metalenses, this challenge becomes far more severe due to exacerbated lateral chromatic aberrations. In this paper, it is demonstrated, for the first time, full-color wide field-of-view imaging using a fisheye metalens coupled with deep learning computational processing. This approach is capable of restoring panoramic images with enhanced signal-to-noise ratio while effectively correcting chromatic aberration, distortion, and vignetting. Furthermore, it is shown that the deep learning algorithm is robust against various lighting conditions and object distances, making it a versatile solution for practical imaging applications involving wide field-of-view metalenses.

Second Harmonic Generation (SHG) has become a critical technique in material characterization, image processing and microscopy. While bulk crystals have been traditionally used for SHG due to their high conversion efficiencies, limited control over radiation properties, delicate phase-matching conditions and alignment pose significant challenges. The exploration of nanoscale materials and structures based on dielectric platforms has provided enhanced SHG efficiency and control, but their limited transparency in the visible spectral range and complex fabrication processes hinder broader application. Barium titanate (BaTiO₃), a ferroelectric material with spontaneous polarization and nonlinear optical behavior, presents an attractive alternative due to its suitability for nano-imprinting techniques, facilitating scalable production of metasurfaces. In this study, SHG from single polycrystalline BaTiO₃ nanocylinders is investigated. Through polarization-dependent experiments, the influence of crystalline domain orientation and arrangements within the nanocylinders on SHG efficiency is characterized. A simplified numerical model to interpret the different polarization-dependent SHG diagrams obtained from nominally identical nanocylinders is developed. The results reveal the significant impact of domain geometry and relative size on SHG characteristics. By understanding the relationship between domain geometry and SHG giving insights into the material characterization and design optimization of BaTiO₃ and other polycrystalline nanostructures in nonlinear optical devices.

Flexible photodetectors have garnered significant attention in recent years due to their potential applications in emerging fields such as artificial intelligence, medical diagnostics, and wearable devices. Quasi-2D perovskites exhibit remarkable optoelectronic properties, excellent environmental stability, and mechanical flexibility, making them promising materials for flexible photodetectors. Achieving precise control over the morphology of these materials is crucial for enhancing device performance. In this study, periodic wrinkle structures are introduced into quasi-2D perovskite films by applying pre-stretching stress to a flexible substrate. These results indicate that these ordered wrinkle structures facilitate grain movement during formation, enabling smaller grains to fill pores and surround larger grains. This process leads to a denser film with a mixed 2D-3D phase architecture, enhancing charge transfer efficiency and prolonging carrier lifetime in the perovskite films. Consequently, the responsivity of the resulting flexible perovskite photodetector significantly increased, reaching 86.7 A W⁻¹, which is 2.5 times higher than that of the unstretched device. Furthermore, the wrinkled structures enhanced mechanical tolerance, allowing the photodetector to retain 80% of its initial responsivity even after 10 000 stretching cycles. These findings highlight the potential of wrinkled structures to significantly enhance the performance of flexible perovskite optoelectronic devices.

Nanometric Ge Films for Ultrafast THz Modulation

Nanometric germanium films, vastly thinner than terahertz wavelengths, have been integrated with a responsive metasurface of metallic terahertz asymmetric split ring resonators on a low-loss flexible substrate (cyclic olefin copolymer film). These ultrathin, flexible, and ultrafast functional metasurfaces enable efficient, low-power terahertz modulation. For further information, see article number 2402010 by Jianqiang Gu, Ranjan Singh, and co-workers.

Heterojunction photodetectors (PDs) with ultrafast response speeds are urgently required for applications in fields such as optical communication and automated production. However, the low separation efficiency of photogenerated carriers owing to interfacial effects (including interfacial defects and barriers) limits the response speed to the order of seconds to milliseconds. Herein, for the first time, an interface-engineered heterostructure is designed with a gradient band alignment to obtain a response speed on the nanosecond scale, where the separation efficiency of the photogenerated carriers is enhanced by Cu-plasmon-induced charge transfer. Cu nanoparticles (NPs) are implanted into the heterojunctions with two different structures: WS₂/CuO@Cu and WS₂@Cu/CuO. Devices with Cu NPs implanted at the interface exhibit an excellent detectivity of 5 × 10¹² Jones and a high responsivity of 979 A W⁻¹. More importantly, an ultrafast response speed of 24 ns is achieved, making it one of the fastest PDs in the field of plasmonic PDs. This high performance is attributed to Cu-plasmon-induced interface engineering, which is confirmed by experiments and theoretical calculations. The interface engineering method proposed in this study provides a new approach for achieving ultrafast PDs.

The low cost and fine-tunability of the luminescence of copper nanoclusters make them attractive candidates for opto-electronic, imaging, and sensing applications; their stability, and a precise understanding of the structure–function correlations however, continue to be challenging. A comprehensive chemical etching strategy is developed to synthesize orange, blue, and cyan emitting nanoclusters from a single source of ultrasmall copper nanoparticles; high quantum yields up to ≈34% are realized. Steady state and time-resolved spectroscopy, electron microscopy, high resolution mass spectrometry, and computational modeling provide critical mechanistic insight into the polychromatic luminescence. A facile method for the fabrication of polymer nanocomposite thin films that sustain and stabilize the luminescent nanoclusters is presented. A subtle variation of the etching strategy without the need to admix multiple components, provides white luminescent thin films with Commission Internationale de l'éclairage (CIE) coordinates, x = 0.35, y = 0.33. The highlights of this work are i) the simple solution synthesis of stable, uniform, and pure ultrasmall Cu nanoparticles, ii) their chemical etching by subtle variations in an optimized protocol to produce highly luminescent, polychromatic nanoclusters, including white-emitting ones, iii) stabilization of the bright luminescent systems in nanocomposite thin films, and iv) a detailed analysis of the luminescence tuning.

Optimized Er-Doped LiNbO₃ Quantum Memory Platform

In the study by Andrej Kuznetsov, Kiwon Moon, and co-workers (see article number 2401374), an optimized approach for fabricating an efficient solid-state photonic quantum memory platform is proposed. This approach relies on dynamic defect annealing occurring in the LiNbO₃ matrix material during its implantation with Er ions at elevated temperatures. The resulting platform, with minimized crystalline disorder and enhanced optical activity, is promising for realizing robust quantum memory with extended storage times and high efficiencies.

Highly Refractive Transparent Half-Heuslers for Near-Infrared Optics

Advanced control of light focusing, reflection, and transmission is possible by using highly refractive transparent materials. In article number 2402295, Akihiro Ishii, Hitoshi Takamura, and co-workers report the discovery of 22 ternary half-Heuslers that exhibit higher refractive indices with wider band gaps than conventional high-refractive-index transparent materials in the near-infrared region. Material design strategies for achieving a high index and wide gap are also explained.

With the advancement of light-emitting diode (LED) display technologies, optical crosstalk has emerged as a significant challenge due to the increasing miniaturization and pixel density of LED arrays. To address this issue, the introduction of a nanorod (NR) optical shield in LED devices is proposed. The shield is fabricated using a straightforward process involving the etching of LED epitaxial layers with self-assembled Ni nanoparticles and a SiO₂ hard mask, resulting in the formation of an NR array. The NR optical shield effectively reduced optical crosstalk by confining light emission to its region, redirecting lateral light into vertical emission and absorbing stray light. This approach offers a practical and efficient solution for reducing optical crosstalk and enhancing the performance of miniaturized LED arrays in advanced display applications.