Resonant Enhancement Research Articles

Entropy as a novel predictor of cardiovascular events in patients with left ventricular noncompaction

BackgroundThe risk stratification of left ventricular noncompaction (LVNC) remains ambiguous. LV entropy derived from late gadolinium enhancement (LGE) in cardiac magnetic resonance (CMR) as a novel measurement of myocardial heterogeneity may serve as the substrate of major adverse cardiovascular events (MACEs). This retrospective study aimed to investigate the value of LV entropy for predicting MACEs in LVNC patients. MethodsConsecutive patients who underwent CMR and met the diagnosis criteria of LVNC were included. All patients were follow-up for MACEs (cardiac death, ventricular arrhythmia requiring therapy or heart failure hospitalization), and their LV entropy derived from the distribution of pixel signal intensities in the LGE of the LV myocardium was analyzed. ResultsOne hundred and forty-three patients (mean age 40 years, 64.3% male) were followed for a median of 3.2 years, and forty-two (29.4%) experienced MACEs. Presenting of symptoms, left ventricular end-diastolic diameter (LVEDD), LV end-diastolic volume (LVEDV) index, LV end-systolic volume (LVESV) index, LV ejection fraction (LVEF), LGE extent, and LV entropy showed association with MACEs. LV entropy maintained independent association with MACEs (HR: 4.76, 95%CI 3.68–5.15, p < 0.001) in multivariable analysis. Entropy was also strong independent predictor of MACEs in patients with and without LGE (HR: 5.89, 95% CI4.18–7.73, p < 0.001; HR: 3.06, 95% CI:1.53–4.80, p = 0.013, respectively). ConclusionsLV entropy can predict MACEs in LVNC patients and provide incremental prognostic value on top of LVEF and LGE. Also, LV entropy may help risk stratification in LGE-negative LVNC patients.

CRGD-Conjugated GdIO Nanoclusters for the Theranostics of Pancreatic Cancer through the Combination of T1-T2 Dual-Modal MRI and DTX Delivery.

Clinically, magnetic resonance imaging (MRI) often uses contrast agents (CAs) to improve image contrast, but single-signal MRI CAs are often susceptible to calcification, hemorrhage, and magnetic sensitivity. Herein, iron acetylacetone and gadolinium acetylacetone were used as raw materials to synthesize a T1-T2 dual-mode imaging gadolinium-doped iron oxide (GdIO) nanocluster. Moreover, to endow the nanoclusters with targeting properties and achieve antitumor effects, the cyclic Arg-Gly-Asp (cRGD) peptide and docetaxel (DTX) were attached to the nanocluster surface, and the efficacy of the decorated nanoclusters against pancreatic cancer was evaluated. The final synthesized material cRGD-GdIO-DTX actively targeted αvβ3 on the surface of Panc-1 pancreatic cancer cells. Compared with conventional passive targeting, the enrichment of cRGD-GdIO-DTX in tumor tissues improved, and the diagnostic accuracy was significantly enhanced. Moreover, the acidic tumor microenvironment triggered the release of DTX from cRGD-GdIO-DTX, thus achieving tumor treatment. The inhibition of the proliferation of SW1990 and Panc-1 pancreatic cancer cells by cRGD-GdIO-DTX was much stronger than that by the untargeted GdIO-DTX and free DTX in vitro. In addition, in a human pancreatic cancer xenograft model, cRGD-GdIO-DTX considerably slowed tumor development and demonstrated excellent magnetic resonance enhancement. Our results suggest that cRGD-GdIO-DTX has potential applications for the precise diagnosis and efficient treatment of pancreatic cancer.

Towards Double Resonant Cavity Enhanced Second Harmonic Generation in Monolayer MoS2

AbstractA characteristic property of monolayered transition metal dichalcogenides is their strong nonlinear response. While they display a high conversion efficiency per atomic layer, due to their low thickness, the absolute value of their nonlinear response remains low. Here enhancement of the second harmonic generation (SHG) of monolayer MoS2 through the design, fabrication, and characterization of a monolithic microcavity, which aims to be double resonant at a fundamental wavelength of λ = 800 nm as well as its second harmonic, is demonstrated. The MoS2 monolayers are embedded in such a cavity, with the aim to simultaneously enhance the light‐matter interaction at the excitation wavelength and the SHG from the monolayers. A resonance enhancement for the SHG process is achieved through the cavity.

Resonance enhancement of the electromagnetic interaction between two charged particles in the bound state in the continuum

In bound states in the continuum (BIC) the mass of a composite particle is greater than the total mass of its constituents. The BIC state is investigated in a system of two charged particles [Formula: see text] and [Formula: see text] with different masses ([Formula: see text]), using the ladder Bethe–Salpeter equation. We demonstrate that there are two momentum space regions for the positive binding energy, in which the electromagnetic interaction between the particles is strongly enhanced, and the effective coupling constant turns out to be equal to [Formula: see text], where [Formula: see text] is the fine structure constant. The interaction resonance confines the constituents in the BIC state with the positive binding energy, which is of the order of the mass of the lighter particle from this pair.

Aluminum Nano Stars with Localized Surface Plasmon Resonance and Field Enhancement

Aim: The Finite Difference Time Domain approach has been used to assess the localised surface plasmon resonance and field enhancement for Al nanostars. The structure's potential as a refractive index sensor has been demonstrated. Background: Research on plasmonics has been possible in a variety of domains, including sensors, SERS, solar cells, and others, due to a tenability in the plasmon wavelength caused by a simple change in shape, size, or external environment. The growth of plasmonics has been greatly aided by the creation of novel ways for creating metallic nanostructures and a large deal of work on the creation of numerical algorithms to cope with arbitrarily shaped metallic nanostructures. The LSPR and field enhancement of an Al nano-star were the main topics of this paper. A larger RIS factor is obtained after adjusting the refractive index sensitivity parameter, making it appropriate for refractive index-based sensor nanostructures. Objective: This study's primary goal is to provide a comparative analysis of the refractive index sensitivity factor for Al nanostars dependent on their size and number of arms. Methods: Al nano star's LSPR and field enhancement have been assessed using the Finite Difference Time Domain (FDTD). Results: By altering the size and number of arms of the nano star, the tenability of the plasmonic peak has been assessed, and it has been found that the peak is sensitive to the ambient dielectric constant. A study has been done on the refractive index sensitivity parameter. A higher sensitivity of about 370 nm/RIU, which is significantly higher than that of other metallic Nanostar (NS), is seen after adjusting the size and number of arms. A wide range of applications is covered by the Al NS field enhancement pattern, which exhibits stronger enhancement with no aggregation at the plasmon peak. Conclusion: For LSPR sensing applications, the impact of modifying the environmental dielectric constant is examined. By changing the size and quantity of the Al NS's arms, we were able to compare the refractive index sensitivity parameter. The bigger size NS exhibits more peaks due to the contribution of the multipole; however, after tuning a number of parameters, better sensitivity in comparison to Au and Ag nanostar has been attained. Al NS can therefore be a promising sensing material for refractive index sensing employing LSPR properties.

Manifestation of “Slow” Light in the Photocurrent Spectra of Ge/Si Quantum Dot Layers Combined with a Photonic Crystal

The spectral characteristics of the photocurrent in the near-infrared range in vertical Ge/Si p–i–n photodiodes with Ge quantum dots embedded in a two-dimensional photonic crystal are investigated. The interaction of the quantum dots with photonic Bloch modes leads to the resonant enhancement of the sensitivity of photodiodes. The dependences of the photocurrent on the angle of incidence of light are used to determine the dispersion relations of the Bloch modes. Regions in the dispersion characteristics where the group velocity of photons is close to zero are revealed. It is established that the maximum enhancement of the photocurrent relative to a photodiode without photonic crystal, which can be up to a factor of ~60, results from the interaction of quantum dots with “slow” Bloch modes.

Optofluidic transport and assembly of nanoparticles using an all-dielectric quasi-BIC metasurface

Manipulating fluids by light at the micro/nanoscale has been a long-sought-after goal for lab-on-a-chip applications. Plasmonic heating has been demonstrated to control microfluidic dynamics due to the enhanced and confined light absorption from the intrinsic losses of metals. Dielectrics, the counterpart of metals, has been used to avoid undesired thermal effects due to its negligible light absorption. Here, we report an innovative optofluidic system that leverages a quasi-BIC-driven all-dielectric metasurface to achieve subwavelength scale control of temperature and fluid motion. Our experiments show that suspended particles down to 200 nanometers can be rapidly aggregated to the center of the illuminated metasurface with a velocity of tens of micrometers per second, and up to millimeter-scale particle transport is demonstrated. The strong electromagnetic field enhancement of the quasi-BIC resonance increases the flow velocity up to three times compared with the off-resonant situation by tuning the wavelength within several nanometers range. We also experimentally investigate the dynamics of particle aggregation with respect to laser wavelength and power. A physical model is presented and simulated to elucidate the phenomena and surfactants are added to the nanoparticle colloid to validate the model. Our study demonstrates the application of the recently emerged all-dielectric thermonanophotonics in dealing with functional liquids and opens new frontiers in harnessing non-plasmonic nanophotonics to manipulate microfluidic dynamics. Moreover, the synergistic effects of optofluidics and high-Q all-dielectric nanostructures hold enormous potential in high-sensitivity biosensing applications.

Measurement of three-photon excitation cross-sections of fluorescein from 1154 nm to 1500 nm.

Measurements of three-photon action cross-sections for fluorescein (dissolved in water, pH ∼11.5) are presented in the excitation wavelength range from 1154 to 1500 nm in ∼50 nm steps. The excitation source is a femtosecond wavelength tunable non-collinear optical parametric amplifier, which has been spectrally filtered with 50 nm full width at half maximum band pass filters. Cube-law power dependance is confirmed at the measurement wavelengths. The three-photon excitation spectrum is found to differ from both the one- and two-photon excitation spectra. The three-photon action cross-section at 1154 nm is more than an order of magnitude larger than those at 1450 and 1500 nm (approximately three times the wavelength of the one-photon excitation peak), which possibly indicates the presence of resonance enhancement.

Extraordinary Five-Wave Mixing in a Zinc Oxide Microwire on a Au Film.

Coherent multiwave mixing is in demand for optical frequency conversion, imaging, quantum information science, etc., but has rarely been demonstrated in solid-state systems. Here, we observed three- and five-wave mixing (5WM) in a c-axis growth zinc oxide microwire on a Au film with picosecond pulses in the near-infrared region. An output 5WM of 4.7 × 10-7 μW, only 2-3 orders smaller than the three-wave mixing, is achieved when the excitation power is as low as 1.5 mW and the peak power density as weak as ∼107 W/cm2. The excitation power dependence of 5WM agrees well with the perturbation limit under the low intensity but exhibits a strong deviation at a high pumping power. This extraordinary behavior is attributed to the cooperative resonant enhancement effect when pumping in the near-infrared range. Our study offers a potential solid-state platform for on-chip multiwave mixing and quantum nonlinear optics, such as generating many-photon entangled states or the construction of photon-photon quantum logic gates.

High-order harmonics generation in Cd and Pd laser-induced plasmas.

We demonstrate the generation of high-order harmonics of laser pulses in palladium and cadmium plasmas. We adjusted the wavelength of driving pulses to investigate the resonance enhancement in different ranges of extreme ultraviolet region. The summation of incommensurate waves during the two-color pump of Pd and Cd plasmas allowed the generation of a broader range of harmonics. The theoretical aspects of the two-color pump of the laser-induced plasma are discussed.

Highly sensitive near-infrared gas sensor system using a novel H-type resonance-enhanced multi-pass photoacoustic cell

A dual-gas sensor system was developed using a H-type resonance-enhanced multi-pass photoacoustic (PA) cell. The sensitivity was improved by the double enhancement of optical path length extension and acoustic resonance. Two silver-coated concave mirrors with a reflectivity of > 95% were fabricated to form a multi-pass PA cell. The laser beam was reflected 24 times to obtain an optical path length of ∼ 3.6 m. The sensor performance was evaluated using a 1572.34 nm laser for CO2 measurement and a 1653.73 nm laser for CH4 measurement. The PA signal amplitude is enhanced by a factor of > 10. The limits of detection of CO2 and CH4 are respectively 20.83 parts per million by volume (ppmv) and 0.43 ppmv. The normalized noise equivalent absorption (NNEA) coefficients are 3.02 × 10−9 cm−1‧W‧Hz−1/2 for CO2 and 9.75 × 10−9 cm−1‧W‧Hz−1/2 for CH4. Online in-situ gas analysis in a coal mine verifies the practicability of the sensor system.

Highly efficient second harmonic generation assisted by the quasi-bound states in the continuum from AlGaAs meta-gratings

Due to the design freedom of metasurfaces in tailoring wavefronts, they have become a general platform for miniaturized functional nonlinear optics. Recently, with the help of the quasi-bound states in the continuum (Q-BIC), the all-dielectric resonance metasurfaces with high quality factor (Q) boost the interaction between pump light and dielectric structure, which have become an effective way to achieve high nonlinear efficiency. Here, an asymmetric grating structure composed of AlGaAs is utilized to enhance the second harmonic generation (SHG) near Q-BIC. By breaking the symmetry of the grating structure, a simple normal incidence linearly polarized plane wave can be treated to excite stronger localized fields within the metasurfaces, allowing strong light–matter​ interactions in nonlinear metasurfaces. Numerical investigations depict that the Q-factor and resonant field enhancement noticed on the metasurface are intimately related to the asymmetric structure of the system. In addition, the high Q-factor resonance facilitates the SHG conversion process in AlGaAs metasurfaces. Especially, for the AlGaAs metasurface with Q-factor of 4.0314 × 104, the conversion efficiency of SHG can reach 10.5% when the pumping intensity is 5 MW/cm 2. This study is of great importance for analyzing the efficient nonlinear metasurfaces with high Q-factors.

High-Order Harmonics Generation in Selenium-Containing Plasmas

The studies of the high-order harmonics generated in Se-containing plasmas are reported. The ablation of selenium in a vacuum allowed for the formation of a plasma demonstrating high-order harmonics generation and resonance enhancement of the harmonic at the shortest wavelength reported so far (λ ≈ 22.9 nm, Eph ≈ 54.14 eV). This harmonic corresponds to the 35th order of the 800-nm-class lasers. The influence of the presence of selenium in the molecular state (ZnSe and HgSe) on the suppression of the resonance effect during harmonics generation in plasma is studied. The enhanced 35th harmonic was analyzed by different methods of plasma formation using nanosecond, picosecond, and femtosecond pulses. The enhancement factor of the resonance-enhanced harmonic was measured to be 32× compared with the neighboring lower-order harmonics in the case of the picosecond-pulses-induced Se plasma. The role of the strong ionic transition of Se in the region of 22.7 nm in the observation of the resonance-induced enhancement of a single harmonic is discussed.

Selective Analysis of Redox Processes at the Electrode Interface with Time-Resolved Raman Spectroscopy.

Electrochemistry and electrochemical reactions are increasingly important in the transition to a sustainable chemical industry. The electron transfer that drives such reactions takes place within nanometers of the electrode surface, and follow-up chemical reactions take place within the diffusion layer. Hence, understanding electrochemical reactions requires time-, potential-, and spatially resolved analysis. The confocal nature of Raman spectroscopy provides high spatial resolution, in addition to detailed information on molecular structure. The intrinsic weakness of nonresonant Raman scattering, however, is not sensitive enough for relatively minor changes to the solution resulting from reactions at the electrode interface. Indeed, the limit of detection is typically well above the concentrations used in electrochemical studies. Here, we show that surface-enhanced Raman scattering (SERS) and resonance Raman (rR) spectroscopy allow for spatially and time-resolved analysis of solution composition at (<1-2 nm) and near (within 5 μm) the electrode surface, respectively, in a selective manner for species present at low (<1 mM) concentrations. We show changes in concentration of species at the electrode surface, without the need for labels, specific adsorption, or resonance enhancement, using a SERS-active gold electrode prepared readily by electrochemical surface roughening. A combination of smooth and roughened gold electrodes is used to distinguish between surface and resonance enhancement using the well-known redox couples ferrocene and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). We discuss the impact of specific adsorption on the spectral analysis with the ruthenium(II) polypyridyl complex, [Ru(bpy)3]2+. The dual function of the electrode (surface enhancement and electron transfer) in the analysis of solution processes is demonstrated with the reversible oxidation of TMA (4,N,N-trimethylaniline), where transient soluble species are identified in real time, with rapid spectral acquisition, making use of localized enhancement. We anticipate that this approach will find use in elucidating electro(catalytic) reactions at electrode interfaces.

Mie Scattering for Photonic Devices

AbstractMie scattering is increasingly exploited to manipulate electromagnetic fields to achieve strong resonant enhancement, to obtain perfect absorption of radiation, and to generate polarization or wavelength selectivity and/or sensitivity. In fact, a multitude of photonic applications are arising that benefit from Mie scattering and have already led to the formation of novel image and hologram schemes or to the design of efficient and compact photodetectors and light sources. Here, the Mie scattering theory for spherical scatterers is reviewed, the basics of the field‐decomposition onto the Mie modes are shown, and dielectric and metallic particles are compared. Recent applications for light spectrum control, detection, non‐linear effects enhancement, and emission are reviewed. How a periodic arrangement of Mie‐scatterers can be utilized to create a strong (in the order of 10 to 100) absorption enhancement in otherwise weakly absorbing layers is also demonstrated. The enhancement dependence on the diameter‐to‐wavelength ratio of the scatterer is analyzed, and how the influence of different Mie‐modes can be distinguished in the periodic array by looking at the field components normal to the scatterer surface is discussed.

Multi-Watt cavity for 266 nm light in vacuum

Intense coherent ultraviolet radiation is gaining increasing importance in advanced quantum technologies—from optical clocks and quantum computers to matter-wave interferometry—as well as in photochemistry, life sciences, semiconductor industry, and space applications. Since the preparation of multi-Watt light sources is still an open challenge for many ultraviolet wavelengths, resonant enhancement in a cavity is an attractive alternative. However, many experiments with atoms, molecules or nanoparticles require isolation in high vacuum where UV optics often show fast degradation. Here, we present stable performance of a cavity for 266 nm light with several Watt of intra-cavity power in high vacuum despite the presence of hydrocarbons. Comparing two sets of cavity mirrors indicates that this feat is connected to the micro-chemical environment at the topmost coating layer. Our study emphasizes the need for further developments in this direction to facilitate robust, compact, and high-performing devices employing UV radiation.

Sensitivity Enhancement of the Surface Plasmon Resonance–Based Gas Sensing by Few Layers of Black Phosphorus

Sensitivity Enhancement of the Surface Plasmon Resonance–Based Gas Sensing by Few Layers of Black Phosphorus

Effect of Monomers and Multimers of Gold Nanostars on Localized Surface Plasmon Resonance and Field Enhancement

Effect of Monomers and Multimers of Gold Nanostars on Localized Surface Plasmon Resonance and Field Enhancement

Si/Organic Integrated Narrowband Near-Infrared Photodetector.

Spectrally selective narrowband photodetection is critical for near-infrared (NIR) imaging applications, such as for communicationand night-vision utilities. It is a long-standing challenge for detectors based on silicon, to achieve narrowband photodetection without integrating any optical filters. Here, this work demonstrates a NIR nanograting Si/organic (PBDBT-DTBT:BTP-4F) heterojunction photodetector (PD), which for the first time obtains the full-width-at-half-maximum (FWHM) of only 26nm and fast response of 74 µs at 895nm. The response peak can be successfully tailored from 895 to 977nm. The sharp and narrow response NIR peak is inherently attributed to the coherent overlapping between the NIR transmission spectrum of organic layer and diffraction enhanced absorption peak of patterned nanograting Si substrates. The finite difference time domain (FDTD) physics calculation confirms the resonant enhancement peaks, which is well consistent with the experiment results. Meanwhile, the relative characterization indicates that the introduction of the organic film can promote carrier transfer and charge collection, facilitating efficient photocurrent generation. This new device design strategy opens up a new window in developing low-cost sensitive NIR narrowband detection.

Second harmonic generation from a-plane GaN vertical monolithic microcavity pumped with femtosecond laser

We have proposed highly efficient microcavity second harmonic generation devices. In this work, we designed and fabricated an a-plane GaN vertical monolithic microcavity second harmonic generation device pumped with a femtosecond laser and obtained normalized wavelength conversion efficiency of 0.15% W−1. The efficiency was comparable to the theoretical estimations taking into account the time evolution of fundamental wave intensity in the microcavity, second harmonic generation and even sum frequency generation. This result indicates the possibility of realizing ultra-compact and ultra-efficient devices pumped with long-pulsed or continuous wave lasers, in which the effect of resonance enhancement is even more pronounced.