ACS Photonics最新文献

Skyrmionic hopfions are three-dimensional quasiparticles discovered in liquid crystals and magnetic materials. Analogous optical hopfions have been studied theoretically and experimentally demonstrated; however, their experimental mapping in a material has been challenging due to their complicated, three-dimensional polarization textures. In this work, we demonstrate the direct projection of the polarization textures of optical hopfions on azopolymers to form surface relief structures via optical radiation pressure. This demonstration offers new insights into the interaction between topologically protected quasiparticles of light and matter.

Disorder is often considered the opposite of order, lacking quantitative methods and being difficult to control. Disordered nanostructures can be conveniently prepared by bottom-up approaches, such as self-assembly, but their intrinsic randomness is often considered to lead to unpredictable results, impeding reproducibility and application. Here, we demonstrate that deterministic, angle-dependent visual appearances induced by specific correlated disorder can be achieved through bottom-up approaches, and reveal plenty of room for tailoring color appearance between order and random disorder. Two unprecedented iridescent visual appearances, backscattering iridescence (rainbow-like color transition covering more than five distinct colors at backscattering angles), and specular iridescent halo (gradual color changes in the visible light range around specular reflection direction), are proposed and demonstrated to be induced by correlated disorder at different degrees, which is regulated by interparticle distance. Besides elucidating the mechanism of iridescence generation, a comprehensive protocol for predicting the color appearance is established, and agrees well with experimental results. Combining bottom-up process, materials with low absorption, and tailored spatial disorder, we have endowed solar cells with colorful appearances, while maintaining the performance, which can serve as a solution for photovoltaic-integrated architectures and vehicles. This study advances the understanding of how disorder shapes color and angular appearance, and will find applications in energy photonics, dazzling arts, and anticounterfeiting.

Mid- and long-wave infrared photodetection is highly desired for various modern optoelectronic devices, but Si-based broadband photodetectors operating at room temperature remain challenging and are being extensively sought. In this paper, a Si-based photodetector with a broadband and fast photoresponse based on the photothermoelectric (PTE) effect of lead telluride (PbTe) film is demonstrated. Large-area, high-crystallinity PbTe film grown by a low-temperature, CMOS-compatible RF magnetron sputtering method is first reported for photodetection. The PbTe PTE photodetector surpasses the energy band gap limitation, operating even at wavelengths exceeding 10 μm. A rapid response time of less than 1 ms is obtained at 1310 nm, which is superior to those of most other reported PTE detectors. Furthermore, the development of a 5 × 5 array device shows a good photoresponse uniformity and demonstrates consistent mid-infrared imaging capabilities at room temperature. Excellent mechanical flexibility enables the integration of wearable optoelectronic devices. This pioneering research paves the way for significant advancements in Si-based broadband photodetector technologies, with potential applications in monolithic integrated detection and imaging systems that operate in visible- to long-wave infrared wavelengths at room temperature.

The presence of large bismuth (Bi) atoms has been shown to increase the spin–orbit splitting energy in bulk GaAsBi, reducing the hole ionization coefficient (β) and thereby reducing the excess noise seen in avalanche photodiodes. In this study, we show that even very thin layers of GaAsBi introduced as quantum wells (QWs) in a GaAs matrix exhibit a significant reduction of β while leaving the electron ionization coefficient, α, largely unchanged. The optical and avalanche multiplication properties of a series of GaAsBi/GaAs multiple quantum well (MQW) p-i-n structures with nominally 5 nm thick, 4.4% Bi GaAsBi QWs, varying from 5 to 63 periods and corresponding barrier widths of 101 to 4 nm were investigated. From photoluminescence, ω-2θ X-ray diffraction, and cross section transmission electron microscopy measurements, the material was found to be of high quality despite the strain introduced by the Bi in all except the samples with 54 and 63 QW periods. Photomultiplication measurements undertaken with different wavelengths showed that α in these MQW structures did not change appreciably with the number of QWs; however, β decreased significantly, especially at lower values, the noise factor, F, is reduced by 58% to 3.5 at a multiplication of 10, compared to a similar thickness bulk GaAs structure without any Bi. This result suggests that Bi-containing QWs could be introduced into the avalanching regions of APDs as a way of reducing their excess noise.