Optical metasurfaces are two-dimensional optical elements composed of dense arrays of subwavelength optical antennas and afford on-demand manipulation of the basic properties of light waves. ...Following the pioneering works on active metasurfaces capable of modulating wave amplitude, there is now a growing interest to dynamically control other fundamental properties of light. Here, we present metasurfaces that facilitate electrical tuning of the reflection phase and polarization properties. To realize these devices, we leverage the properties of actively controlled plasmonic antennas and fundamental insights provided by coupled mode theory. Indium–tin–oxide is embedded into gap-plasmon resonator-antennas as it offers electrically tunable optical properties. By judiciously controlling the resonant properties of the antennas from under- to overcoupling regimes, we experimentally demonstrate tuning of the reflection phase over 180°. This work opens up new design strategies for active metasurfaces for displacement measurements and tunable waveplates.
Enhancing and spectrally controlling light absorption is of great practical and fundamental importance. In optoelectronic devices consisting of layered semiconductors and metals, absorption has ...traditionally been manipulated with the help of Fabry-Pérot resonances. Even further control over the spectral light absorption properties of thin films has been achieved by patterning them into dense arrays of subwavelength resonant structures to form metafilms. As the next logical step, we demonstrate electrical control over light absorption in metafilms constructed from dense arrays of actively tunable plasmonic cavities. This control is achieved by embedding indium tin oxide (ITO) into these cavities. ITO affords significant tuning of its optical properties by means of electrically-induced carrier depletion and accumulation. We demonstrate that particularly large changes in the reflectance from such metafilms (up to 15% P) can be achieved by operating the ITO in the epsilon-near-zero (ENZ) frequency regime where its electrical permittivity changes sign from negative to positive values.
Surface plasmon (SP) excitations in metals facilitate confinement of light into deep-subwavelength volumes and can induce strong light-matter interaction. Generally, the SP resonances supported by ...noble metal nanostructures are explained well by classical models, at least until the nanostructure size is decreased to a few nanometres, approaching the Fermi wavelength λ
of the electrons. Although there is a long history of reports on quantum size effects in the plasmonic response of nanometre-sized metal particles, systematic experimental studies have been hindered by inhomogeneous broadening in ensemble measurements, as well as imperfect control over size, shape, faceting, surface reconstructions, contamination, charging effects and surface roughness in single-particle measurements. In particular, observation of the quantum size effect in metallic films and its tuning with thickness has been challenging as they only confine carriers in one direction. Here, we show active tuning of quantum size effects in SP resonances supported by a 20-nm-thick metallic film of indium tin oxide (ITO), a plasmonic material serving as a low-carrier-density Drude metal. An ionic liquid (IL) is used to electrically gate and partially deplete the ITO layer. The experiment shows a controllable and reversible blue-shift in the SP resonance above a critical voltage. A quantum-mechanical model including the quantum size effect reproduces the experimental results, whereas a classical model only predicts a red shift.
The ability to split an incident light beam into separate wavelength bands is central to a diverse set of optical applications, including imaging, biosensing, communication, photocatalysis, and ...photovoltaics. Entirely new opportunities are currently emerging with the recently demonstrated possibility to spectrally split light at a subwavelength scale with optical antennas. Unfortunately, such small structures offer limited spectral control and are hard to exploit in optoelectronic devices. Here, we overcome both challenges and demonstrate how within a single-layer metafilm one can laterally sort photons of different wavelengths below the free-space diffraction limit and extract a useful photocurrent. This chipscale demonstration of anti-Hermitian coupling between resonant photodetector elements also facilitates near-unity photon-sorting efficiencies, near-unity absorption, and a narrow spectral response (∼ 30 nm) for the different wavelength channels. This work opens up entirely new design paradigms for image sensors and energy harvesting systems in which the active elements both sort and detect photons.
The ability of two nearly-touching plasmonic nanoparticles to squeeze light into a nanometer gap has provided a myriad of fundamental insights into light-matter interaction. In this work, we ...construct a nanoelectromechanical system (NEMS) that capitalizes on the unique, singular behavior that arises at sub-nanometer particle-spacings to create an electro-optical modulator. Using in situ electron energy loss spectroscopy in a transmission electron microscope, we map the spectral and spatial changes in the plasmonic modes as they hybridize and evolve from a weak to a strong coupling regime. In the strongly-coupled regime, we observe a very large mechanical tunability (~250 meV/nm) of the bonding-dipole plasmon resonance of the dimer at ~1 nm gap spacing, right before detrimental quantum effects set in. We leverage our findings to realize a prototype NEMS light-intensity modulator operating at ~10 MHz and with a power consumption of only 4 fJ/bit.
We explore the shape-dependent light scattering properties of silicon (Si) nanoblocks and their physical origin. These high-refractive-index nanostructures are easily fabricated using planar ...fabrication technologies and support strong, leaky-mode resonances that enable light manipulation beyond the optical diffraction limit. Dark-field microscopy and a numerical modal analysis show that the nanoblocks can be viewed as truncated Si waveguides, and the waveguide dispersion strongly controls the resonant properties. This explains why the lowest-order transverse magnetic (TM01) mode resonance can be widely tuned over the entire visible wavelength range depending on the nanoblock length, whereas the wavelength-scale TM11 mode resonance does not change greatly. For sufficiently short lengths, the TM01 and TM11 modes can be made to spectrally overlap, and a substantial scattering efficiency, which is defined as the ratio of the scattering cross section to the physical cross section of the nanoblock, of ∼9.95, approaching the theoretical lowest-order single-channel scattering limit, is achievable. Control over the subwavelength-scale leaky-mode resonance allows Si nanoblocks to generate vivid structural color, manipulate forward and backward scattering, and act as excellent photonic artificial atoms for metasurfaces.
Background
Allergic inflammation affects the epithelial cell populations resulting in goblet cell hyperplasia and decreased ciliated cells. Recent advances in single‐cell RNA sequencing (scRNAseq) ...have enabled the identification of new cell subtypes and genomic features of single cells. In this study, we aimed to investigate the effect of allergic inflammation in nasal epithelial cell transcriptomes at the single‐cell level.
Methods
We performed scRNAseq in cultured primary human nasal epithelial (HNE) cells and in vivo nasal epithelium. The transcriptomic features and epithelial cell subtypes were determined under IL‐4 stimulation, and cell‐specific marker genes and proteins were identified.
Results
We confirmed that cultured HNE cells were similar to in vivo epithelial cells through scRNAseq. Cell‐specific marker genes were utilized to cluster the cell subtypes, and FOXJ1+‐ciliated cells were sub‐classified into multiciliated and deuterosomal cells. PLK4 and CDC20B were specific for deuterosomal cells, and SNTN, CPASL, and GSTA2 were specific for multiciliated cells. IL‐4 altered the proportions of cell subtypes, resulting in a decrease in multiciliated cells and loss of deuterosomal cells. The trajectory analysis revealed deuterosomal cells as precursor cells of multiciliated cells and deuterosomal cells function as a bridge between club and multiciliated cells. A decrease in deuterosomal cell marker genes was observed in nasal tissue samples with type 2 inflammation.
Conclusion
The effects of IL‐4 appear to be mediated through the loss of the deuterosomal population, resulting in the reduction in multiciliated cells. This study also newly suggests cell‐specific markers that might be pivotal for investigating respiratory inflammatory diseases.
This study investigates the effect of allergic inflammation in nasal epithelial cell transcriptomes at the single‐cell level. The effects of IL‐4 appear to be mediated through the loss of the deuterosomal population, resulting in the reduction in multiciliated cells. The trajectory analysis reveals deuterosomal cells as precursor cells of multiciliated cells. Common ciliated cell marker (FOXJ1), multiciliated cell marker (CCNO), and deuterosomal cell markers (CDC20 and CDK1) are reduced by IL‐4 treatment; IL‐13 shows similar inhibitory effect.Abbreviations: CCNO, cyclin O; CDC20, cell division cycle 20; CDK1, cyclin‐dependent kinase 1; CTRL, control; FOXJ1, forkhead box J1; IL, interleukin; RNAseq, RNA sequencing
Accumulating electrons in transparent conductive oxides such as indium tin oxide (ITO) can induce an "epsilon-near-zero" (ENZ) in the spectral region near the important telecommunications wavelength ...of λ = 1.55 μm. Here we theoretically demonstrate highly effective optical electro-absorptive modulation in a silicon waveguide overcoated with ITO. This modulator leverages the combination of a local electric field enhancement and increased absorption in the ITO when this material is locally brought into an ENZ state via electrical gating. This leads to large changes in modal absorption upon gating. We find that a 3 dB modulation depth can be achieved in a non-resonant structure with a length under 30 μm for the fundamental waveguide modes of either linear polarization, with absorption contrast values as high as 37. We also show a potential for 100 fJ/bit modulation, with a sacrifice in performance.
Composites based on carbon nanotubes (CNTs) are promising patternable materials that can be engineered to incorporate the outstanding properties of CNTs into various applications via printing ...technologies. However, conventional printing methods for CNTs require further improvement to overcome the major drawbacks that limit the patterning resolution and target substrate. Herein, an intaglio contact printing method based on a CNT/paraffin composite is presented for realizing highly precise CNT network patterns without restrictions on the substrate. In this method, the CNT/paraffin composite can be patterned with a high resolution (<10 µm) and neatly transferred onto various substrates with a wide range of surface energies, including human skin. The patterned composite exhibits high durability against structural deformations, and structural damage caused by fatigue accumulation can be cured in a few seconds. In addition, miniaturized sensing and energy‐harvesting applications are demonstrated with high performances. The present method facilitates the rapid fabrication of highly precise interdigitated electrodes via one‐step printing, enabling high‐performance operation and miniaturization of the devices. It is anticipated that these results will not only spur the further development of various applications of CNTs but also contribute to advances in soft lithography methods applicable to many fields of science and engineering.
An intaglio contact printing method is presented for realizing highly integrated electrodes based on carbon nanotube composites without restrictions on the substrate. This method facilitates the printing of high‐resolution patterned electrodes onto various substrates in a controlled manner. The printed electrodes exhibit high durability and thermal healing abilities. Miniaturized sensing and energy‐harvesting applications are also demonstrated with high performances.
The optical properties of semiconductors are typically considered intrinsic and fixed. Here we leverage the rapid developments in the field of optical metamaterials to create ultrathin semiconductor ...metafilms with designer absorption spectra. We show how such metafilms can be constructed by placing one or more types of high-index semiconductor antennas into a dense array with subwavelength spacings. It is argued that the large absorption cross-section of semiconductor antennas and their weak near-field coupling open a unique opportunity to create strongly absorbing metafilms whose spectral absorption properties directly reflect those of the individual antennas. Using experiments and simulations, we demonstrate that near-unity absorption at one or more target wavelengths of interest can be achieved in a sub-50-nm-thick metafilm using judiciously sized and spaced Ge nanobeams. The ability to create semiconductor metafilms with custom absorption spectra opens up new design strategies for planar optoelectronic devices and solar cells.
PDF
