Type-I Heterojunction Photodetectors In article number 2400190, Yingjian Wang, Liang Li, Dongfeng Shi, and co-workers present type I van der Waals heterojunction photodetectors that demonstrate exceptional optoelectronic performance, characterized by a broadband spectral response spanning from ultraviolet to near-infrared regions, ultrafast response kinetics, and superior photoresponsivity. These advanced photodetectors, when synergistically combined with state-of-the-art Hadamard single-pixel imaging technology, enable high-fidelity image reconstruction across extensive spectral ranges and under challenging environmental conditions.

Multimodal optical microscopy can be used to visualize multiple biological targets at the same location and at similar spatial resolutions, enabling more comprehensive studies of complex biological samples. However, current multimodal imaging systems typically use multiple or specially designed excitation lasers. Furthermore, previous studies have reported only three or four types of imaging modalities, limiting the number of imaging targets. This study develops an imaging system based on a single commercialized 1550 nm fiber laser and integrates five imaging modalities: second harmonic generation, third harmonic generation, two‐photon fluorescence, three‐photon fluorescence, and reflected confocal microscopy. Utilizing the characteristics of different imaging modalities, various biological components in biological tissues can be revealed simultaneously and cell movement in a complex biological environment can be traced noninvasively. The capacity of deep imaging has also been demonstrated in the mouse brain. The results show that the proposed multimodal microscopy system has great application potential in biomedical fields, such as tumor diagnosis and immunotherapy.

Analyzing or probing a complex‐structured light field with a simple model to obtain its mode composition sequence and phase delays among eigenmodes is challenging. Currently, there are numerous methods for calculating the weight and analyzing the amplitude of structured light eigenmodes, particularly on orbital angular momentum light field. However, the complete mode spectrum decomposition including the eigenmodes’ indexes with the intensity coefficients and relatively phase delays still needs the comprehensive solution. In this work, the diffractive optical method to extract the complete information of complex‐structured light field composed by eigenmodes superimposed state is detailly designed and proved. Through the interference between the inverse conversion of eigenmodes in the Fourier domain, complete mode spectrum can be constructed with eigenmode ordinals, amplitude weight coefficients, and relative phases. To the best of the knowledge, this marks the inaugural use of a simple computational hologram method to fully decompose the mode spectrum information, thereby obtaining more crucial intrinsic information about the intermode phases without additional efforts. This approach on analyzation and description can serve as a vital general tool for analyzing the intensity, phase, and Poynting vector field of complex‐structured light fields.

With the rapid development of communication networks and computing, optical switches as an important elementary unit are highly needed. In this article, a silicon‐based optical switch with (GST)‐enabled phase‐shifting region is proposed. This optical switch is based on contra‐directional couplers composed of two phase‐shifted Bragg gratings. To minimize the impact of GST absorption loss, GST is only used in the phase‐shifting area, and the switching function is achieved by changing the state of GST. In the results, it is shown that the proposed device has a 3 dB operation bandwidth of about 163.2 GHz (1.394 nm) and an extinction ratio of about 19.06 dB for the drop port and about 20.25 dB for the through port. The loss at the central operational wavelength is about 1.3 and 1.04 dB for the through port and the drop port, respectively, and the largest loss over the entire operation bandwidth for these two ports is 1.66 and 2.35 dB. Furthermore, the optical switch is shown to be bidirectional, achieving similar performance when light propagates in the opposite direction. Compared with previous works, the proposed optical switch realizes wider operation bandwidth, higher extinction ratio, and lower loss.

It is very challenging to achieve highly efficient and low roll‐off purple to deep‐blue organic light‐emitting diodes (OLEDs) due to the limited selection of suitable emitters. Herein, a series of Ir(III) phosphors‐bearing purinylidene‐based N‐heterocyclic carbene (NHC) chelates are reported, namely, f‐ct2a–d, which have successfully turned the emission peak maxima to the purple region (427–432 nm) in degassed toluene, together with high quantum yields of 77%–81%. Notably, f‐ct2b is further employed as the phosphorescent dopant in the fabrication of OLEDs to afford deep‐blue emission paking at 448 nm and an EQE of 6.7% at 100 cd m−2. Furthermore, a true‐blue hyperphosphorescent OLED with 21 wt% of f‐ct2a as sensitizer and 1 wt% of ν‐DABNA as terminal emitter is also fabricated, giving excellent performance with max. EQE up to 22.2% and an EQE of 19.2% at a brightness of 100 cd m−2.

Herein, a holographic optical element (HOE) printing technique which maintains shapes and sizes of hogels across diverse focal positions, and aberration‐corrected HOEs which are fabricated by it are proposed. The proposed HOE printer employs nonpixelated focus modulators composed of double 4f optics in reference and signal beam paths to record hogels with the consistent shapes, which is validated via the ray tracing simulation. An optimization algorithm is developed for aberration‐corrected HOEs, dedicated to the proposed printing system. Imaging simulations verify the improved image quality compared to a baseline case by showing a 5 times sharper point spread function. As the experimental verification, a HOE printer is realized, which provides 1 × 1 mm of hogels consistently over 20° × 20° of angular ranges and 8 diopters of focal length changes. Displaying experiments using printed HOEs (mono‐colored and full‐colored ones) verify the proposed method with aberration‐corrected and see‐through images.

Halide perovskite solar cells (PSCs) have shown remarkable power conversion efficiencies. However, the inherent defect issues of perovskite materials still limit their performance and long‐term stability, resulting in lifespans far from commercial standards. With their noninvasive approach to probing the electronic and vibrational properties of materials, spectroscopic techniques have become crucial tools for uncovering and understanding defect states and complex charge carrier dynamics in halide perovskites. This review explores the application of various advanced spectroscopic techniques in PSCs to elucidate the complex behaviors of charge carriers within PSCs. These techniques reveal detailed temporal and spatial distributions of charge carriers, enabling precise analysis of defect impacts and interfacial charge transfer processes. By integrating spectroscopic data, it is possible to more accurately identify and mitigate defect‐induced nonradiative recombination and charge transfer, thereby enhancing the stability and efficiency of PSCs. This comprehensive spectroscopic understanding is crucial for developing innovative technologies to accelerate the commercial viability of PSCs.

Graphene‐based absorbers have various modern applications across industries due to their exceptional properties. Some common applications include: thermal management and energy storage. Herein, the design and simulation of a broadband tunable absorber based on graphene with perfect absorption spectra in the near‐infrared region are reported. The proposed structure consists of an MgF2 layer and golden disc surrounded by L‐shaped golden arms placed on single layer of graphene. The structure guarantees polarization‐insensitive (PI) performance under normal incident due to the symmetrical design. The investigation of the PI of the structure reveals almost similar absorption for oblique incident angles up to 55° for TM and up to 60° for TE polarization. The desirable resonance wavelength is achievable by tuning the geometrical parameters. By changing the chemical potential of graphene, the absorption and bandwidth of absorber are controllable. A full width at half maximum of 330 nm is another superiority of this absorber. These considerable aspects of the proposed structure make it practical for varieties of applications such as cloaking, sensing, switching, and so on.

The AlGaN materials system has been extensively studied in order to improve the efficiency of UV‐B and UV‐C light‐emitting diodes (LEDs). While progress has been made, significant challenges remain at shorter wavelengths. Most notably, increased Al composition for shorter‐wavelength operation results in increased activation energy of Mg dopants, resulting in low p‐doping. Although p‐doped h‐BN, with a bandgap of 5.9 eV, has been proposed as a potential replacement of p‐doped AlGaN, there have not been demonstrations of LEDs fabricated from p‐doped h‐BN/AlGaN heterostructures. Such unique heterostructures combine 2D p‐doped h‐BN materials with 3D AlGaN materials. Herein, fabrication and characterization of p‐doped h‐BN/AlGaN multiple quantum wells (MQWs)/n‐AlGaN LEDs, demonstrating emission of light at 290 nm corresponding to the AlGaN MQWs, with weaker emission at 262 nm corresponding to the AlGaN barrier, are reported. These results conclusively show hole injection through p‐doped h‐BN into AlGaN and provide a proof of concept that p‐doped h‐BN can be an alternative hole injection layer for UV LEDs.