Electrical source of surface plasmon polaritons based on hybrid Au-GaAs QW structures

In this paper, the electrical excitation of surface plasmon polaritons (SPPs) based on a hybrid metal-semiconductor quantum well (QW) structure is investigated by finite-difference time-domain The hybrid structure could serve as a plasmonic source for integrated plasmonic circuits

Lasing Action with Gold Nanorod Hyperbolic Metamaterials

Coherent nanoscale photon sources are of paramount importance to achieving all-optical communication. Several nanolasers smaller than the diffraction limit have been theoretically proposed and experimentally demonstrated using plasmonic cavities to confine optical fields. Such compact cavities exhibit large Purcell factors, thereby enhancing spontaneous emission, which feeds into the lasing mode. However, most plasmonic nanolasers reported so far have employed resonant nanostructures and therefore had the lasing restricted to the proximity of the resonance wavelength. Here, we report on an approach based on gold nanorod hyperbolic metamaterials for lasing. Hyperbolic metamaterials provide broadband Purcell enhancement due to large photonic density of optical states, while also supporting surface plasmon modes to deliver optical feedback for lasing due to nonlocal effects in nanorod media. We experimentally demonstrate the advantage of hyperbolic metamaterials in achieving lasing action by its comparison with that obtained in a metamaterial with elliptic dispersion. The conclusions from the experimental results are supported with numerical simulations comparing the Purcell factors and surface plasmon modes for the metamaterials with different dispersions. We show that although the metamaterials of both types support lasing, emission with hyperbolic samples is about twice as strong with 35% lower threshold vs. the elliptic ones. Hence, hyperbolic metamaterials can serve as a convenient platform of choice for nanoscale coherent photon sources in a broad wavelength range

Coherent Optical Sources with Novel Metamaterials

Since its invention in 1960, the laser has seen tremendous developments and has quickly revolutionized fundamental and applied fields such as metrology, medicine, data storage, fabrication and telecommunications among others. With the ever growing need for data transfer speeds and compact devices, considerable efforts have been made towards miniaturizing the laser for on-chip integration. While photonic cavities have proven to exhibit high-Q factors enabling strong feedback for lasing, their miniaturization to the nanoscale is not viable since the diffraction limit requires the cavity length to be at least half the lasing wavelength. Plasmonic nanostructures, supporting electron oscillations coupled with photons, have led to the designs of optical components and optoelectronic devices in the deep subwavelength regime. In particular, a new class of lasers based on surface plasmon amplification by stimulated emission of radiation, spaser, has been proposed which holds record-small mode volume. In Additional, plasmonic nanoparticles provide larger magnitude of the scattering cross section than the dielectric particles with the same dimensions. Hence, plasmonic nanoparticles offer new opportunities in controlling a random laser that relies on multiple scattering of light to provide the optical feedback. In the scope of this work, we will utilize novel plasmonic metamaterials, to achieve coherent optical sources, including plasmonic nanolasers and plasmonic random lasers, and to engineer the properties. We demonstrated plasmonic random lasers with improved figure-of-merits through plasmonic nanorod metamaterials which hold great advantages in mode confinements and imaging applications when compared to dielectric random lasers. Metamaterials with hyperbolic dispersions have been shown to support more profound plasmonic resonances for lasing than those with elliptic dispersions. Besides plasmonic metamaterials, we have introduced a novel material platform, two-dimensional Ti3C2Tx MXene, to achieve advance control over random lasing properties. By taming the optical properties of the Ti3C2Tx MXene flakes, reduced gain threshold and dynamically tunable random lasing modes have been demonstrated. In addition to designing coherent optical sources, we also constructed plasmonic metasurfaces to manipulate the properties of the emission. A broadband high-efficiency half-wave plate has been demonstrated to change the polarization state of light

Broadband High-Efficiency Half-Wave Plate: A Supercell-Based Plasmonic Metasurface Approach

We design, fabricate, and experimentally demonstrate an ultrathin, broadband half-wave plate in the near-infrared range using a plasmonic metasurface. The simulated results show that the linear polarization conversion efficiency is over 97% with over 90% reflectance across an 800 nm bandwidth. Moreover, simulated and experimental results indicate that such broadband and high-efficiency performance is also sustained over a wide range of incident angles. To further obtain a background-free half-wave plate, we arrange such a plate as a periodic array of integrated supercells made of several plasmonic antennas with high linear polarization conversion efficiency, consequently achieving a reflection-phase gradient for the cross-polarized beam. In this design, the anomalous (cross-polarized) and the normal (copolarized) reflected beams become spatially separated, hence enabling highly efficient and robust, background-free polarization conversion along with broadband operation. Our results provide strategies for creating compact, integrated, and high-performance plasmonic circuits and devices

Severe Burn Injury Significantly Alters the Gene Expression and m6A Methylation Tagging of mRNAs and lncRNAs in Human Skin

N6-methyladenosine (m6A) modulates RNA metabolism and functions in cell differentiation, tissue development, and immune response. After acute burns, skin wounds are highly susceptible to infection and poor healing. However, our understanding of the effect of burn injuries on m6A methylation and their potential mechanism is still limited. Human m6A-mRNA&lncRNA Epitranscriptomic microarray was used to obtain comprehensive mRNA and lncRNA transcriptome m6A profiling and gene expression patterns after burn injuries in human skin tissue. Bioinformatic and functional analyses were conducted to find molecular functions. Microarray profiling showed that 65 mRNAs and 39 lncRNAs were significantly hypermethylated; 5492 mRNAs and 754 lncRNAs were significantly hypomethylated. Notably, 3989 hypomethylated mRNAs were down-expressed and inhibited many wound healing biological processes and pathways including in the protein catabolic process and supramolecular fiber organization pathway; 39 hypermethylated mRNAs were up-expressed and influenced the cell surface receptor signaling pathway and inflammatory response. Moreover, we validated that m6A regulators (METTL14, METTL16, ALKBH5, FMR1, and HNRNPC) were significantly downregulated after burn injury which may be responsible for the alteration of m6A modification and gene expression. In summary, we found that homeostasis in the skin was disrupted and m6A modification may be a potential mechanism affecting trauma infection and wound healing

Quantum Dot-Based Local Field Imaging Reveals Plasmon-Based Interferometric Logic in Silver Nanowire Networks

We show that the local electric field distribution of propagating plasmons along silver nanowires can be imaged by coating the nanowires with a layer of quantum dots, held off the surface of the nanowire by a nanoscale dielectric spacer layer. In simple networks of silver nanowires with two optical inputs, control of the optical polarization and phase of the input fields directs the guided waves to a specific nanowire output. The QD-luminescent images of these structures reveal that a complete family of phase-dependent, interferometric logic functions can be performed on these simple networks. These results show the potential for plasmonic waveguides to support compact interferometric logic operations

Highly Broadband Absorber Using Plasmonic Titanium Carbide (MXene)

Control of light transmission and reflection through nanostructured materials has led to demonstration of metamaterial absorbers that have augmented the performance of energy harvesting applications of several optoelectronic and nanophotonic systems. Here, for the first time, a broadband plasmonic metamaterial absorber is fabricated using two-dimensional titanium carbide (Ti₃C₂T_<i>x</i>) MXene. Arrays of nanodisks made of Ti₃C₂T_<i>x</i> exhibit strong localized surface plasmon resonances at near-infrared frequencies. By exploiting the scattering enhancement at the resonances and the optical losses inherent to Ti₃C₂T_<i>x</i> MXene, high-efficiency absorption (∼90%) for a wide wavelength window of incident illumination (∼1.55 μm) has been achieved

Induction of defense in cereals by 4-fluorophenoxyacetic acid suppresses insect pest populations and increases crop yields in the field

Synthetic chemical elicitors, so called plant strengtheners, can protect plants from pests and pathogens. Most plant strengtheners act by modifying defense signaling pathways, and little is known about other mechanisms by which they may increase plant resistance. Moreover, whether plant strengtheners that enhance insect resistance actually enhance crop yields is often unclear. Here, we uncover how a mechanism by which 4-fluorophenoxyacetic acid (4-FPA) protects cereals from piercing-sucking insects and thereby increases rice yield in the field. Four-FPA does not stimulate hormonal signaling, but modulates the production of peroxidases, H2O2, and flavonoids and directly triggers the formation of flavonoid polymers. The increased deposition of phenolic polymers in rice parenchyma cells of 4-FPA-treated plants is associated with a decreased capacity of the white-backed planthopper (WBPH) Sogatella furcifera to reach the plant phloem. We demonstrate that application of 4-PFA in the field enhances rice yield by reducing the abundance of, and damage caused by, insect pests. We demonstrate that 4-FPA also increases the resistance of other major cereals such as wheat and barley to piercing-sucking insect pests. This study unravels a mode of action by which plant strengtheners can suppress herbivores and increase crop yield. We postulate that this represents a conserved defense mechanism of plants against piercing-sucking insect pests, at least in cereals