Narrowband photodetection is an important measurement technique for material analysis and sensing, for example, nondispersive infrared sensing technique. Both photoactive material engineering and nanophotonic filtering schemes have been explored to realize wavelength-selective photodetection, while most devices have a responsive bandwidth larger than 2% of the operating wavelength, limiting sensing performance. Near-infrared photodetection with a bandwidth of less than 0.2% of the operating wavelength was demonstrated experimentally in Au/Si Schottky nanojunctions. A minimum linewidth of photoelectric response down to 2.6 nm was obtained at a wavelength of 1550 nm by carefully tailing the absorptive and radiative loss in the nanostructures. Multiple functions were achieved on chip with the corrugated Au film, including narrowband resonance, light harvesting for sensing and photodetection, and electrodes for hot electron emission. Benefiting from such a unity integration with in situ photoelectric conversion of the optical sensing signal and the ultranarrowband resonance, self-contained on-chip biosensing via simple intensity interrogation was demonstrated with a limit of detection down to 0.0047% in concentration for glucose solution and 150 ng / mL for rabbit IgG. Promising potential of this technique is expected for the applications in on-site sensing, spectroscopy, spectral imaging, etc.

Germanene nanostrips (GeNSs) have garnered significant attention in modern semiconductor technology due to their exceptional physical characteristics, positioning them as promising candidates for a wide range of applications. GeNSs exhibit a two-dimensional (buckled) honeycomb-like lattice, which is similar to germanene but with controllable bandgaps. The modeling of GeNSs is essential for developing appropriate synthesis methods as it enables understanding and controlling the growth process of these systems. Indeed, one can adjust the strip width, which in turn can tune the bandgap and plasmonic response of the material to meet specific device requirements. In this study, the objective is to investigate the electronic behavior and THz plasmon features of GeNSs (≥100 nm wide). A semi-analytical model based on the charge-carrier velocity of freestanding germanene is utilized for this purpose. The charge-carrier velocity of freestanding germanene is determined through the GW approximation (vF m·s^?1). Within the width range of 100 to 500 nm, GeNSs exhibit narrow bandgaps, typically measuring only a few meV. Specifically, upon analysis, it was found that the bandgaps of the investigated GeNSs ranged between 29 and 6 meV. As well, these nanostrips exhibit q-like plasmon dispersions, with their connected plasmonic frequency (≤30 THz) capable of being manipulated by varying parameters such as strip width, excitation plasmon angle, and sample quality. These manipulations can lead to frequency variations, either increasing or decreasing, as well as shifts towards larger momentum values. The outcomes of our study serve as a foundational motivation for future experiments, and further confirmation is needed to validate the reported results.

Interfacial solar steam generation (ISSG) is a novel and potential solution to global freshwater crisis. Here, based on a facile sol-gel fabrication process, we demonstrate a highly scalable Janus aramid nanofiber aerogel (JANA) as a high-efficiency ISSG device. JANA performs near-perfect broadband optical absorption, rapid photothermal conversion and effective water transportation. Owning to these features, efficient desalination of salty water and purification of municipal sewage are successfully demonstrated using JANA. In addition, benefiting from the mechanical property and chemical stability of constituent aramid nanofibers, JANA not only possesses outstanding flexibility and fire-resistance properties, but its solar steaming efficiency is also free from the influences of elastic deformations and fire treatments. We envision JANA provides a promising platform for mass-production of high-efficiency ISSG devices with supplementary capabilities of convenient transportation and long-term storage, which could further promote the realistic applications of ISSG technology.

Surface plasmons (SPs) are electromagnetic surface waves that propagate at the interface between a conductor and a dielectric. Due to their unique ability to concentrate light on two-dimensional platforms and produce very high local-field intensity, SPs have rapidly fueled a variety of fundamental advances and practical applications. In parallel, the development of metamaterials and metasurfaces has rapidly revolutionized the design concepts of traditional optical devices, fostering the exciting field of meta-optics. This review focuses on recent progress of meta-optics inspired SP devices, which are implemented by the careful design of subwavelength structures and the arrangement of their spatial distributions. Devices of general interest, including coupling devices, on-chip tailoring devices, and decoupling devices, as well as nascent SP applications empowered by sophisticated usage of meta-optics, are introduced and discussed.

The lateral geometry and material property of plasmonic nanostructures are critical parameters for tailoring their optical resonance for sensing applications. While lateral geometry can be easily observed by a scanning electron microscope or an atomic force microscope, characterizing materials properties of plasmonic devices is not straightforward and requires delicate examination of material composition, cross-sectional thickness, and refractive index. In this study, a deep neural network is adopted to characterize these parameters of unknown plasmonic nanostructures through simple transmission spectra. The network architecture is established based on simulated data to achieve accurate identification of both geometric and material parameters. We then demonstrate that the network training by a mixture of simulated and experimental data can result in correct material property recognition. Our work may indicate a simple and intelligent characterization approach to plasmonic nanostructures by spectroscopic techniques.

We propose a chip-integratable cylindrical vector (CV) beam generator by integrating six plasmonic split ring resonators (SRRs) on a planar photonic crystal (PPC) cavity. The employed PPC cavity is formed by cutting six adjacent air holes in the PPC center, which could generate a CV beam with azimuthally symmetric polarizations. By further integrating six SRRs on the structure defects of the PPC cavity, the polarizations of the CV beam could be tailored by controlling the opening angles of the SRRs, e.g., from azimuthal to radial symmetry. The mechanism is governed by the coupling between the resonance modes in SRRs and PPC cavity, which modifies the far-field radiation of the resonance mode of the PPC cavity with the SRR as the nano-antenna. The integration of SRRs also increases the coupling of the generated CV beam with the free-space optics, such as an objective lens, promising its further applications in optical communication, optical tweezer, imaging, etc.

亚波长人工微纳结构，诸如超构材料和超构表面等，可以实现很多天然材料所不具备的新颖光学性质，为电磁波的操控提供有效手段。但基于静态结构而研制出的光学材料和器件往往只具有固定的光学功能，难以应对复杂多变的实际应用需求。近年来，人们将二氧化钒等相变材料引入人工微纳结构，实现了一系列可调光学材料和器件，其性能可实时改变和动态控制。本文回顾了二氧化钒的结构、相变机制及其物理特性等研究，展示了热、电、光等激发方式对二氧化钒相变的调控，系统总结了基于二氧化钒相变实现动态可调亚波长光学材料和器件的研究进展，期望推动发展新型亚波长动态可调的光电功能材料和器件。