Advanced Optical Materials最新文献

Terahertz (THz) radiation is a powerful probe of low-energy excitations in all phases of matter. However, it remains a challenge to find materials that efficiently generate THz radiation in a broad range of frequencies following optical excitation. Here, we investigate a pyroelectric material, ZnSnN₂, and find that its above-band-gap excitation results in the efficient formation of an ultrafast photocurrent generating THz radiation. The resulting THz electric field spans a frequency range from below 1 THz to above 30 THz. The results suggest that the photocurrent is primarily driven by an ultrafast pyroelectric effect where the photo-excited carriers screen the spontaneous electric polarization of ZnSnN₂. Strong structural disorder reduces the photocarrier lifetime significantly and, thus, enables broadband operation. ZnSnN₂ shows a similar THz-emitter performance as the best spintronic THz emitters regarding bandwidth and amplitude. The study unveils the large potential of pyroelectric materials as efficient and broadband THz emitters with built-in bias fields.

Lead halide perovskites are promising next-generation optoelectronic materials due to their solution processability, tunable bandgap and excellent photoelectric properties. However, achieving deep-blue emission in all-inorganic CsPbX₃ nanocrystals remains challenging due to phase separation, halide volatilization and insufficient stability, limiting industrial application. Herein, a collaborative strategy of “chlorine source regulation—defect passivation—fiber integration” is proposed. By incorporating β-cyclodextrin chloride (βCD-Cl) into CsPbBr₃, we synthesized large-scale deep-blue CsPbBr_3-xCl_x@βCD-Cl microcrystals via a mechanosynthesis route. Flexible blue-light fiber films are fabricated via electrospinning, showing a photoluminescence quantum yield (PLQY) of 55.79% and excellent environmental stability, with only a 16 nm red shift observed after 171 days in water. Additionally, the fiber films enable near-infrared (750 nm)-to-blue photon upconversion (450-490 nm), achieving unprecedented bilirubin degradation efficiency (40% within 20 min). They can serve as core components for next-generation phototherapeutic blankets, combining spectral selectivity (blocking harmful radiation < 420 nm) with therapeutic light transmission, eliminating neonatal retinal phototoxicity risks without requiring protective eyewear. The full solution-processed white-light fiber film is prepared, with CIE coordinates (x = 0.32, y = 0.34) near the ideal white light point. Overall, this study clarifies the molecular structure—performance relationships, overcomes stability bottlenecks, and supports photodynamic therapy and bio-photonic devices.

The earth-abundant II-IV-nitrides ZnSnN₂ and ZnGeN₂ are direct bandgap semiconductors with a wurtzite-derived crystal structure. Their alloys, ZnSn_xGe_{1 − x}N₂, have bandgaps tunable across the full visible spectrum, making them interesting for many optoelectronic applications. Here, electrical, structural, and optical properties of near-stoichiometric ZnSn_xGe_{1 − x}N₂ alloys, i.e., where [Zn]/([Zn]+[Ge]+[Sn]) ≈ 0.5, are reported, for samples synthesized by reactive magnetron sputtering. These results reveal unprecedentedly high electrical mobilities in Ge-rich alloys, with values of 136 and 400 cm²/Vs at room-temperature and ≈100 K, respectively. The bandgaps are determined from optical absorption measurements combined with hybrid density functional calculations and reveal a significant Burstein–Moss shift in the Sn rich alloys. Finally, band alignments are determined in the sputter-grown thin films by combining optical transmission measurements, hybrid density functional calculations, and UV photoelectron spectroscopy measurements, where the bandgap variation is predominantly caused by a shift of the conduction band edge. This work elucidates in unprecedented detail the tuning of optical and electrical properties in ZnSn_xGe_{1 − x}N₂ by variation of the chemical composition, where bandgap values of alloys with x ∈ [0.5−0.7] are suitable for top cell absorbers in two-terminal tandem solar cells assuming a Si bottom cell.

Controllable Method for Synaptic Nano-Device

In the Research Article (DOI: 10.1002/adom.202502484), Jianya Zhang, Yonglin Huang, Yukun Zhao, and co-workers report a controllable method to integrate single nanowire into synaptic nano-device with ultralow power consumption. It can mimic multiple functions of biological synapses for learning, corresponding to those in cover image. Due to the advantages of simplicity and cost-efficiency, this method has a promising prospect.

Composite Grating Metasurface

A composite grating metasurface, composed of alternating deep-subwavelength nanostrips of anisotropic α-MoO₃ and isotropic SiC, enables precise topological control of polaritons, whose dispersion transitions between elliptical and hyperbolic by tailoring the grating orientation or material composition. More details can be found in the Research Article by Hanchao Teng, Na Chen, Hai Hu, and co-workers (DOI: 10.1002/adom.202502073).

Achieving independent modulation of distinct spectral characteristics in adaptive multispectral camouflage devices remains a key challenge. Drawing inspiration from the skin textures of felines, this research developed a biomimetic array electrode to enable independent visible-infrared modulation. This is achieved using Prussian blue and MXene/CNT hybrid slurry as functional layers, which respectively modulate visible and infrared regions. Significant differences in optical response ranges and operating principles among the different functional layers provide a foundation for the device's independent modulation. The impact of visual integration between the two functional layers is analyzed via the contour area ratio, while infrared camouflage performance is comprehensively evaluated by analyzing their infrared temperature and chromaticity coordinate differences. The results indicate that the minimum distance required for contour recognition varies with array size. For instance, when a device with an array size of 0.6 mm is observed from a distance of 120 cm, the contour area ratios are only 3.4% (visible region) and 2.1% (infrared region), with a maximum temperature difference of 2.12 °C, which is far below the threshold required for contour detection by detection devices. This research provides crucial insights to advance the development of independent modulation adaptive multispectral camouflage technology.

Artificial neural networks underpin modern artificial intelligence but face challenges of scalability, energy consumption, and hardware efficiency as model sizes grow. Photonic approaches offer an attractive alternative by exploiting the parallelism and low thermal footprint of light, yet many implementations still require complex device fabrication or engineered nonlinearities. Extreme learning machines (ELMs) simplify this paradigm by fixing the input-to-hidden mapping and training only a linear output layer, making them highly compatible with physical realizations. Here, a photonic ELM (PELM) framework is introduced based on ultrafast transient absorption (TA) spectroscopy, a widely adopted pump–probe technique operating intrinsically on the femtosecond–picosecond timescale. In this system, inputs are encoded through multiple probe-polarization channels, each parameterized by pump–probe delay, and the resulting TA spectral responses provide high-dimensional nonlinear features without pixelated modulators or nanofabrication. Using a quasi-1D ZrSe₃ nanoribbon, task versatility is demonstrated across nonlinear regression, spiral classification, and image recognition. The approach achieves near-perfect accuracy on the Iris dataset and robust performance on MNIST digits, underscoring the potential of TA-based encoding for physical computation. These results establish ultrafast TA spectroscopy as an experimentally accessible platform and lay the groundwork for future ultrafast, energy-efficient photonic learning systems.

Optically Active Nanocrystals

With this special issue, friends and former group members wish to honor Prof. Luis Liz Marzán on the occasion of his 60th birthday. His pioneering work in metallic colloidal chemistry and bionanoplasmonics has left a lasting legacy, both scientifically and personally, through his roles as a mentor and colleague (see also the Guest Editorial, DOI: 10.1002/adom.202503590). This front cover illustrates a variety of colloidal metallic nanocrystal shapes, including chiral nanoparticles, that have been reported by Luis's group over the years. Exploring synthesis protocols for the shape control of plasmonic nanoparticles, along with investigating their optical properties and applications in biosensing and therapy, has been the major research direction of Prof. Luis Liz Marzán.

Nanoparticle Assembly

A laser focused at the substrate/liquid interface in a dispersion of plasmonic gold nanorods leads to an optically-generated thermal gradient which drags the nanorods towards the hot region, where their interactions with a dispersed polymer then result in adhesion onto the glass substrate in a circular pattern around the laser spot. More details can be found in the Research Article by Eric H. Hill and co-workers (DOI: 10.1002/adom.202500375).

Achieving efficient optical coupling between the emission from perovskite quantum dots (PQDs) and photonic integrated elements requires ultranarrow linewidths and highly directional emission. These are challenging goals at room temperature due to the broad and isotropic nature of perovskite emission. Here, we demonstrate ultranarrow-linewidth emission from CsPbBr₃ PQDs at room temperature, in both spontaneous and stimulated regimes, by coupling to state-of-the-art open-access curved dielectric cavities under continuous wave excitation. The emission is confined to a single transverse electromagnetic mode of the cavity, achieving a remarkably narrow linewidth of 0.2 nm, ≈100× narrower than free-space emission in both the emission regime. Single-mode lasing from a small number of PQDs is observed, yielding a quality factor of ≈2590, among the highest reported for single-mode lasing. The open-access design enables precise tuning of cavity length and selective coupling of emitters in their native state, overcoming the limitations associated with closed and fixed-length vertical-cavity surface emitting laser geometries. The geometry's low divergence and tunability provide an efficient route for integrating perovskite emitters with on-chip photonic circuits, advancing their use in quantum and optoelectronic technologies.