Enhanced trapping properties induced by strong LSPR-exciton coupling in plasmonic tweezers.

Plasmonic tweezers break the diffraction limit and enable trap the deep-subwavelength particles. However, the innate scattering properties and the photothermal effect of metal nanoparticles pose challenges to their effective trapping and the non-damaging trapping of biomolecules. In this study, we investigate the enhanced trapping properties induced by strong coupling between localized surface plasmon resonances (LSPR) and excitons in plasmonic tweezers. The LSPR-exciton strong coupling exhibits an anticrossing behavior in dispersion curves with a markable Rabi splitting of 196 meV. Plasmonic trapping forces on excitons experience a significant increase within this strong coupling system due to higher longitudinal enhancement of electric field enhancement, which enables efficient particle trapping using lower laser power and minimizes ohmic heat generation. Moreover, leveraging strong coupling effects allows the successful trapping of a 50 nm Au particle coated with J-aggregates, overcoming previous limitations associated with scattering characteristics and smaller size that hindered effective metal nanoparticle manipulation. These findings open up new possibilities for the nondestructive trapping of biomolecules and metal nanoparticles across various applications.

Numerical study on a random plasmonic laser in the metal-insulator-metal structure.

This Letter proposes a random plasmonic laser in the metal-insulator-metal (MIM) structure, in which the dielectric core with gain is dispersed with circular dielectric nanoscatterers. The numerical results from finite-difference time-domain simulation indicate that scattering by the randomly distributed dielectric nanoscatterers in the MIM waveguide provides feedback to the random laser with surface plasmon. The design bypasses the requirement of a distributed feedback structure for the plasmonic waveguide-based nanolasers, which is challenging and expensive in fabrication. Additionally, the MIM structure makes this type of random laser easily applicable to nanoscale integrated photonic devices and circuits.

Distinct ultrafast carrier dynamics of α-In2Se3 and ß-In2Se3: contributions from band filling and bandgap renormalization.

As an intrigued layered 2D semiconductor material, indium selenide (In2Se3) has attracted widespread attention due to its excellent properties. So far, the carrier dynamics of α-In2Se3 and ß-In2Se3 are still lacking a comprehensive understanding, which is essential to enhancing the performance of In2Se3-based optoelectronic devices. In this study, we explored the ultrafast carrier dynamics in thin α-In2Se3 and ß-In2Se3via transient absorption microscopy. For α-In2Se3 with a narrower bandgap, band filling and bandgap renormalization jointly governed the time evolution of the differential reflectivity signal, whose magnitude and sign at different delays were determined by the weights between the band filling and bandgap renormalization, depending on the carrier density. For ß-In2Se3, whose bandgap is close to the probe photon energy, only positive differential reflectivity was detected, which was attributed to strong band filling effect. In both materials, the lifetime decreased and the relative amplitude of the Auger process increased, when the pump fluence was increased. These findings could provide further insights into the optical and optoelectronic properties of In2Se3-based devices.

Reversible photoluminescence modulation of monolayer MoS2 on a ferroelectric substrate by light irradiation and thermal annealing.

Monolayer semiconducting two-dimensional (2D) materials are strongly emerging materials for exploring the spin-valley coupling effect and fabricating novel optoelectronic devices due to their unique structural symmetry and band structures. Due to their atomic thickness, their excitonic optical response is highly sensitive to the dielectric environment. In this work, we present a novel approach to reversibly modulate the optical properties of monolayer molybdenum disulfide (MoS2) via changing the dielectric properties of the substrate by laser irradiation and thermal annealing. We chose LiNbO3 as the substrate and recorded the PL spectra of monolayer MoS2 on LiNbO3 substrates with positive (P+) and negative (P-) ferroelectric polarities. A distinct PL intensity of the A peak was observed due to opposite doping by surface charges. Under light irradiation, the PL intensity of monolayer MoS2 on P+ Fe2O3-doped LiNbO3 gradually decreased with time due to the reduction of intrinsic p-doping, which originated from the drift of photo-excited electrons under a spontaneous polarization field and accumulation on the surface. The PL intensity was found to be restored by thermal annealing which could erase the charge redistribution. This study provides a strategy to reversibly modulate the optical properties of monolayer 2D materials on top of ferroelectric materials.

Differential expression of microRNAs in tomato leaves treated with different light qualities.

BACKGROUND: Light is the main source of energy and, as such, is one of the most important environmental factors for plant growth, morphogenesis, and other physiological responses. MicroRNAs (miRNAs) are endogenous non-coding RNAs that contain 21-24 nucleotides (nt) and play important roles in plant growth and development as well as stress responses. However, the role of miRNAs in the light response is less studied. We used tomato seedlings that were cultured in red light then transferred to blue light for 2 min to identify miRNAs related to light response by high-throughput sequencing. RESULTS: A total of 108 known miRNAs and 141 predicted novel miRNAs were identified in leaf samples from tomato leaves treated with the different light qualities. Among them, 15 known and 5 predicted novel miRNAs were differentially expressed after blue light treatment compared with the control (red light treatment). KEGG enrichment analysis showed that significantly enriched pathways included zeatin biosynthesis (ko00908), homologous recombination (ko03440), and plant hormone signal transduction (ko04075). Zeatin biosynthesis and plant hormone signal transduction are related to plant hormones, indicating that plant hormones play important roles in the light response. CONCLUSION: Our results provide a theoretical basis for further understanding the role of miRNAs in the light response of plants.

Impact of the pitch angle on the spin Hall effect of light weak measurement.

The spin Hall effect of light (SHEL), as a photonic analogue of the spin Hall effect, has been widely studied for manipulating spin-polarized photons and precision metrology. In this work, a physical model is established to reveal the impact of the interface pitch angle on the SHEL accompanied by the Imbert-Fedorov angular shift simultaneously. Then, a modified weak measurement technique is proposed in this case to amplify the spin shift experimentally, and the results agree well with the theoretical prediction. Interestingly, the amplified transverse shift is quite sensitive to the variation of the interface pitch angle, and the performance provides a simple and effective method for precise pitch angle sensing with a minimum observable angle of 6.6 × 10-5°.

Electrically tunable polarization of random lasing from dye-doped nematic liquid crystals.

Tunable polarizing direction of random lasing emission by an applied electric field which radiated from the lateral end face of homogeneously aligned, dye-doped nematic liquid crystal (NLC) cell was demonstrated for the first time, to the best of our knowledge. The lasing emission was partially polarized in the direction along the director of the NLC without the applied electric field. By tuning the applied electric field, the NLC director could be rotated to arbitrary direction from homogeneous to homeotropic alignment, resulting in the polarizing direction of lasing emission to any direction from parallel to perpendicular to the substrate surface in the end face.

Ultrafast volume holographic recording with exposure reciprocity matching for TI/PMMAs application.

The range of exposure for which the holographic reciprocity law holds in photopolymers, is mainly dependent on the light exposure intensity and polymerization rate between photo-initiator and monomers. Matching this is the key to improving performance. Characterization of the dependence on diffraction efficiency of the volume transmission gratings on holographic reciprocity matching of TI/PMMAs under different milliseconds with different thickness (1-3mm) has been carried out for the novel high-sensitive TI/PMMA polymers. Diffraction gratings can be recorded in TI/PMMAs under 20ms with the exposure intensity of 115mW/cm2. The physical and chemical mechanism under and after single shot exposure is analyzed which can be divided into three parts, namely, photo-induced polymerization, dark diffusion of photosensitive molecules, and counter-diffusion of photoproducts. Holographic properties of TI/PMMAs of different thickness (1-3mm) under different shingle-shot durations and repetition rates are investigated in detail as well. The diffraction efficiency reaches 67% with the response time of 15.69s. By this way, volume holographic gratings with no reciprocity failure can be recorded under multi-pulse exposure, with high grating strength and rapid sensitivity in TI/PMMAs, which indicates the volume holographic memories have the potential for recording and storing transient information in life and in the military.

High efficiency active wavefront manipulation of spin photonics based on a graphene metasurface.

Metasurfaces have been widely studied for manipulating light fields. In this work, a novel metasurface element is achieved with a high circular polarization amplitude conversion efficiency of 88.5% that creates an opposite phase shift ranging from -180° to 180° between incidence and reflection for different spin components. By arranging the elements according to different requirements, spin-dependent reflection, focusing and scattering are demonstrated. It is also demonstrated that tuning of the Fermi energy is an viable way to active control the circular polarization conversion efficiency and expand the applicable bandwidth. The results open a new route for modifying and designing the wavefront of circular polarized light.

Porous Molybdenum Carbide Nanostructures Synthesized on Carbon Cloth by CVD for Efficient Hydrogen Production.

Molybdenum carbide (Mo2 C) is a promising noble-metal-free electrocatalyst for the hydrogen evolution reaction (HER), due to its structural and electronic merits, such as high conductivity, metallic band states and wide pH applicability. Here, a simple CVD process was developed for synthesis of a Mo2 C on carbon cloth (Mo2 C@CC) electrode with carbon cloth as carbon source and MoO3 as the Mo precursor. XRD, Raman, XPS and SEM results of Mo2 C@CC with different amounts of MoO3 and growth temperatures suggested a two-step synthetic mechanism, and porous Mo2 C nanostructures were obtained on carbon cloth with 50 mg MoO3 at 850 °C (Mo2 C-850(50)). With the merits of unique porous nanostructures, a low overpotential of 72 mV at current density of 10 mA cm-2 and a small Tafel slope of 52.8 mV dec-1 was achieved for Mo2 C-850(50) in 1.0 m KOH. The dual role of carbon cloth as electrode and carbon source resulted into intimate adhesion of Mo2 C on carbon cloth, offering fast electron transfer at the interface. Cyclic voltammetry measurements for 5000 cycles revealed that Mo2 C@CC had excellent electrochemical stability. This work provides a novel strategy for synthesizing Mo2 C and other efficient carbide electrocatalysts for HER and other applications, such as supercapacitors and lithium-ion batteries.

Holographic response characteristics influenced by an absorptive diffusion polymerization model in bulk TI/PMMAs.

Dynamic formation of a volume holographic grating is mainly caused by the diffusion polymerization of a photoinitiator in TI/poly-(methyl methacrylates) (PMMAs). Here, we consider the time-dependent absorption coefficient in this material to establish an absorption modulated diffusion polymerization model. An experimental and theoretical investigation in TI/PMMAs with different sample thicknesses (1-3 mm) is presented. It is indicated that the thickness can regulate the holographic sensitivity and constancy in TI/PMMAs. Furthermore, we also examined the dark diffusion process, multiplexed gratings recording, pre-exposure holographic enhancement, and long-term full exposure in TI/PMMAs with different thicknesses to analyze their holographic sensitivity and constancy. It is predicted that, in general, the absorption characteristics in TI/PMMA can be further affected by changing its thickness, thus it is able to satisfy different requirements in high-density holographic memories.

Ultrafast volume holographic storage on PQ/PMMA photopolymers with nanosecond pulsed exposures.

Ultrafast holographic recording in bulk phenanthrenequinone dispersed poly (methyl methacrylate) photopolymers is experimentally examined under nanosecond pulsed exposure. A modified interference optical system is set to investigate the dark enhancement effect and real-time diffraction grating strength. Single transmission diffraction grating is recorded in a 6 nanosecond pulse exposure. Grating enhancement formation with different pulse quantity, repetition rate and spatial frequency are also measured. Diffraction efficiency is enhanced by increasing the pulse number as well as the single-pulse energy. The grating strength of 0.58 within 1.8 µs cumulative exposure time is obtained. Moreover, holographic reciprocity failure occurring in the ultrafast holographic storage is analyzed. This paper presents a practical support for PQ/PMMA photopolymers in applications of transient information holographic storage.

Improvement of ultrafast holographic performance in silver nanoprisms dispersed photopolymer.

This work demonstrates the grating formation of bulk nanoparticle polymer composites through an improved interference optical system under ultrafast nanoseconds exposure of a silver nanoprisms (NPs) dispersed photo-polymerizable mixture in the case of 532 nm wavelength. The polymerizable mixture is composed of phenathrenequinone (PQ) (photoinitiator) and methyl methacrylate (MMA) (monomer). The mechanism in this bulk nanoparticle polymer composite is analyzed by mixing nonlocal polymerization driven diffusion (NPDD) model and absorption modulation caused by the spatial concentration distribution difference of silver NPs. We find that the attenuation of diffraction efficiency under pulsed exposure is due to the reciprocity law failure. This work presents an analysis of the cause of reciprocity failure and improvement in holographic properties by doping silver NPs. The optimized photopolymer presents diffraction efficiencies as high as 51.4% with 1.8 µs cumulative pulsed exposure. Cumulative gratings strength is also enhanced by 70% while doping silver NPs under 1.5 µs cumulative pulsed exposure.

A computational study on a multimode spin conductance switching by coordination isomerization in organometallic single-molecule junctions.

Single-molecule junctions provide the additional flexibility of tuning the on/off conductance states through molecular design. Here, we focus on a family of organometallic complexes with a conjugated curved buckybowl as the ligand. Using first-principles calculations, a multi-mode reversible spin switching based on the CpFe·corannulene complex is predicted by the temperature control of the CpFe+ coordination position in corannulene. The different spin conductance states for three coordinated modes are ascribed to the different electronic spin states of the organometallic complex due to crystal field effects. The predicted relative stabilities of isomers and the energy barriers of isomerization reactions can ensure that the conversion among the three isomers can occur quickly and, at a specific temperature, a dominant isomer has a higher proportion than the other two isomers. This provides a new framework for understanding transport in organometallic complexes with localized d states. This presents an exciting opportunity for exploiting junctions involving molecular spin switching.

Double-helix PnLin chains: novel potential nonlinear optical materials.

The structures, circular dichroism (CD) spectra and nonlinear optical (NLO) responses of a series of inorganic double-helix chains, PnLin (n = 6-12), have been investigated using the quantum chemistry method. P-P and P-Li interactions play a major role in stabilizing double-helix chains. The distinctive CD spectra of the double-helix frameworks (namely, a sharp negative CD band at short-wavelength region and a positive CD band at long-wavelength region) become obvious with increasing number of PLi units. The NLO response augments with the length of the double-helix chains, and the contribution of the axial component along the chain direction gradually becomes crucial simultaneously. Synergistic effects, a decrease of crucial electronic transition energies and charge transfer excitation give rise to enhanced NLO responses. In particular, the electronic transitions from the highest occupied molecular orbital to the lowest unoccupied molecular orbital make significant contributions not only to the positive CD bands in the long-wavelength region, but also to the NLO responses of the double-helix PnLin (n = 6-12) chains.

Two-dimensional atom localization based on coherent field controlling in a five-level M-type atomic system.

We study two-dimensional sub-wavelength atom localization based on the microwave coupling field controlling and spontaneously generated coherence (SGC) effect. For a five-level M-type atom, introducing a microwave coupling field between two upper levels and considering the quantum interference between two transitions from two upper levels to lower levels, the analytical expression of conditional position probability (CPP) distribution is obtained using the iterative method. The influence of the detuning of a spontaneously emitted photon, Rabi frequency of the microwave field, and the SGC effect on the CPP are discussed. The two-dimensional sub-half-wavelength atom localization with high-precision and high spatial resolution is achieved by adjusting the detuning and the Rabi frequency, where the atom can be localized in a region smaller thanλ/10×λ/10. The spatial resolution is improved significantly compared with the case without the microwave field.

Tunable spin Hall effect of light with graphene at a telecommunication wavelength.

The spin Hall effect of light (SHEL) has been widely studied for manipulating spin-polarized photons. In this Letter, we present a mechanism to tune the spin shift of the SHEL electrically at 1550 nm by means of introducing a graphene layer. The spin shift is quite sensitive to a graphene layer near the Brewster angle for horizontal polarization incidence and can be dynamically tuned by varying the Fermi energy of graphene. We find that the position of the Brewster angle and the value of the spin shift are decided by the real and imaginary parts of graphene conductivity, respectively. In addition, two different tuned regions have been revealed: one is the "step-like switch" region where the spin shift switches between two values, and the other is the "negative modulation" region where the spin shift declines gradually as the Fermi energy increases. These findings may provide a new paradigm for a tunable spin photonic device.

Laboratory simulation of laser propagation through plasma sheaths containing ablation particles of ZrB2-SiC-C during hypersonic flight.

The optical communication method has potential for solving the blackout problem, which is a big challenge faced in the development of aerospace. Two laser transmission systems were set up to explore the influence of the plasma and the ablation particles on the propagation of the laser. The experimental results indicate that the laser can transmit through the plasma with little attenuation. When there are ablation particles of ZrB2-SiC-C added in the plasma, the intensity of the laser has fluctuations. The work introduced in this Letter can be regarded as basic research of the propagation characters of the laser through plasma sheaths.

De novo assembly and characterization of the Welsh onion (Allium fistulosum L.) transcriptome using Illumina technology.

Welsh onion (Allium fistulosum L.) has long been cultivated as a vegetable and spice for its flavor and aroma. However, transcriptomic and genomic data for A. fistulosum remain scarce. The goal of this study was to generate transcript sequences for functional genomic analyses, and identify genes potentially involved in sulfur, selenium, and vitamin metabolism. In total, 53,378,674 high-quality reads were generated, and de novo assembly resulted in 103,286 contigs and 53,837 unigenes. The average unigene length was 619 bp with an N50 of 832 bp. Similarity searches revealed that 36,155 sequences were similar to those of known proteins in public databases. Of these, 35,250 unigenes sequences were significantly similar to sequences in the NCBI non-redundant protein database and 22,804 were annotated in the Swiss-Prot database. Additionally, 13,125 and 26,660 unigenes were annotated in the Cluster of Orthologous Group and Gene Ontology databases, respectively. A total of 20,680 unigenes were classified into 128 pathways via functional annotation against the Kyoto Encyclopedia of Genes and Genomes pathway database. Key enzymes involved in sulfur and selenium metabolism were also identified. Additionally, our transcriptome revealed a number of unigenes encoding important enzymes involved in vitamin metabolism. We also identified 2014 simple sequence repeats in 1892 unigenes. This transcriptome analysis provides valuable information to further our understanding of the molecular mechanisms regulating the biosynthesis of organic sulfur compounds. The detected simple sequence repeats may facilitate marker-assisted selection in Welsh onion breeding experiments.

Fast coherent manipulation of quantum states in open systems.

We present a method to manipulate quantum states in open systems. It is shown that a high-fidelity quantum state may be generated by designing an additional Hamiltonian without rotating wave approximation. Moreover, we find that a coherent transfer is possible using quantum feedback control even when feedback parameters and noise strength can not be exactly controlled. Our results demonstrate the feasibility of constructing the shortcuts to adiabatic passage beyond rotating wave approximation in open systems.