Structural Resonance Research Articles

Adsorbate Resonance Induces Water-Metal Bonds in Electrochemical Interfaces.

This study delves into the intricate interactions between surface-near species, OH and H2O, on electrodes in electrochemical interfaces. These species are an inevitable part of many electrocatalytic energy conversion reactions such as the oxygen reduction reaction. In our modeling, we utilize high statistics on a dataset of complex solid solutions with high atomic variability to show the emergence of H2O-metal covalent bonds under specific conditions. Based on density functional theory (DFT) calculations ofadsorption energies onmany thousands of different surface compositions, we provide a quantifiable physical understanding of this induced water covalency, which is rooted in simple quantum mechanics. Directional hydrogen bonding between surface-near H2O and OH, enables surface bonding electrons to delocalize mediatedby near-symmetrical adsorbate resonance structures. The different adsorbate resonance structures differ by surface coordination explaining the induced H2O-metal bonding.

Adsorbate Resonance Induces Water‐Metal Bonds in Electrochemical Interfaces

This study delves into the intricate interactions between surface‐near species, OH and H2O, on electrodes in electrochemical interfaces. These species are an inevitable part of many electrocatalytic energy conversion reactions such as the oxygen reduction reaction. In our modeling, we utilize high statistics on a dataset of complex solid solutions with high atomic variability to show the emergence of H2O‐metal covalent bonds under specific conditions. Based on density functional theory (DFT) calculations of adsorption energies on many thousands of different surface compositions, we provide a quantifiable physical understanding of this induced water covalency, which is rooted in simple quantum mechanics. Directional hydrogen bonding between surface‐near H2O and OH, enables surface bonding electrons to delocalize mediated by near‐symmetrical adsorbate resonance structures. The different adsorbate resonance structures differ by surface coordination explaining the induced H2O‐metal bonding.

Recent Progress in Electro‐Optic Modulators: Physical Phenomenon, Structures Properties, and Integration Strategy

AbstractElectro‐optic modulators (EOMs), serving as indispensable components within photonic integrated circuits, are essential for enabling energy‐efficient, high‐speed, and high‐capacity optical communication systems. This review illustrates the principal physical phenomenon exploited in EOMs and provides a comprehensive analysis of the cutting‐edge EOMs featuring interference structures (Mach–Zehnder modulators and Michelson‐interferometer modulators) and resonance structures (microring modulators, racetrack modulators, and photonic crystal modulators). The comparative analysis of the performance merits and limitations in EOMs is presented, highlighting the combination of diverse electro‐optic material compositions with different optical structures, which reveals a promising integration strategic so as to pursue a trade‐off in modulation performance. It is contributed to the ongoing discourse on optimizing EOMs for the subsequent communication technologies and the advancement of photonic chips.

Excitation of high-quality quasi-BIC toroidal mode in a lattice perturbed terahertz metasurface

The bound state in continuum (BIC) is a phenomenon that describes the existence of nonradiative modes (dark modes) embedded in the continuum frequency range. However, an ideal BIC cannot be detected experimentally. The BIC can be transformed into a quasi-BIC by establishing a leaky channel to the radiation continuum. In this study, instead of the conventional asymmetric split ring resonator structure, a sharp quasi-BIC mode is excited in a symmetric split ring resonator (SRR) metasurface by the perturbation of the lattice constant of the unit cell via changing the interspacing distance between two adjacent SRRs. The quality factor of the quasi-BIC mode can be tuned by varying the interspacing of two SRRs, while the resonance frequency of the quasi-BIC mode remains stable. An eigenmode analysis confirms the presence of the quasi-BIC mode, while the ab initio Fano theory and a coupled oscillator model elucidate the radiative and nonradiative coupling mechanisms. The influence of geometric perturbations on the quasi-BIC mode is quantitatively assessed through the extracted fitting parameters, providing insights into the transition from the dark mode (ideal BIC) to the quasi-BIC mode. The terahertz time domain spectroscopy measurement demonstrates a signature of the quasi-BIC resonance mode as a result of the band folding in the first Brillouin zone induced by the doubling of the lattice constant.

All-optical simultaneous OR and AND optical logic gates based on nonlinear photonic crystal ring resonator

Abstract An all-optical simultaneous OR and AND logic gates using the nonlinear Kerr effect and ring resonator based on a two-dimensional photonic crystal are proposed in this paper. The proposed structure has a resonant wavelength of 1551.3 nm and a power consumption (1 kW/μm2). The proposed structure is suitable for all-optical photonic integrations because of its simplicity and small size (23 μm x 30.4 μm). Moreover, the structure executes two logic operations without requiring an additional spare/control signal through a single structure, making fabrication easy. The total footprint of the photonic crystal ring resonator structure measures approximately 699 μm². A very high contrast ratio of 26.10 dB and 25.34 dB is obtained for the OR and AND logic gates, with response times equal to 2 ps and 0.67 ps, respectively. In addition, the calculated bit rates for OR and AND logic gates are approximately 0.5 and 1.5 Tbps, respectively. Using the Rsoft CAD commercial software, the FullWAVE and BandSOLVE module of the software is used for numerical and theoretical investigation of the structure.

Two-dimensional valley photonic crystal resonant cavities

Introducing defects in photonic crystals is a common method for manipulating and controlling the propagation of electromagnetic waves. By introducing defects in photonic crystal waveguides, the periodicity of the waveguide structure can be disrupted, local modes can be formed, and resonant cavity functions can be achieved. In this study, we designed two groups of two-dimensional valley photonic crystal waveguides, each of which uses different methods to introduce defects and obtained different resonant cavity structures, and designed a resonant cavity sensor. We conducted a detailed theoretical analysis of the resonant cavity through simulation software. In addition, we fabricated the samples and conducted microwave experiments to demonstrate the accuracy of our theoretical research. Our research provides guidance for the application of photonic crystal devices.

Ultrasensitive liquid sensor based on an embedded microchannel bulk acoustic wave resonator

The high-frequency and high-quality factor characteristics of bulk acoustic wave (BAW) resonators have significantly advanced their application in sensing technologies. In this work, a fluidic sensor based on a BAW resonator structure is fabricated and investigated. Embedded microchannels are formed beneath the active area of the BAW device without the need for external processes. As liquid flows through the microchannel, pressure is exerted on the upper wall (piezoelectric film) of the microchannel, which causes a shift in the resonant frequency. Using density functional theory, we revealed the intrinsic mechanism by which piezoelectric film deformation influences BAW resonator performance. Theoretically, the upwardly convex piezoelectric film caused by liquid flow can increase the resonant frequency. The experimental results obtained with ethanol solutions of different concentrations reveal that the sensor, which operates at a high resonant frequency of 2.225 GHz, achieves a remarkable sensitivity of 5.1 MHz/% (221 ppm/%), with an ultrahigh linearity of 0.995. This study reveals the intrinsic mechanism of liquid sensing based on BAW resonators, highlights the potential of AlN/Al0.8Sc0.2N composite film BAW resonators in liquid sensing applications and offers insights for future research and development in this field.

CMOS-compatible plasmonic magnetic field sensor: An alternative approach using ultra-compact MIM configuration

This paper introduces a novel magnetic field sensor (MFS) that utilizes a metal-insulator-metal (MIM) waveguide integrated with a resonator structure and incorporates water-based Fe3O4 magnetic fluid. The sensor uses titanium nitride (TiN) as the plasmonic material which offers numerous advantages over conventional noble plasmonic materials. The sensor takes advantage of the tunable optical properties of the magnetic fluid and TiN to detect changes in the external magnetic field and quantify the magnetic field strength which has been demonstrated using the Finite Element Method (FEM). Our proposed MFS exhibits a high sensitivity of 11.97 pm/Oe, a narrow-band full-width half maximum of 93.66 nm, and a resolution of 8.36 × 10−4 Oe. The sensor is also compatible with complementary metal oxide semiconductor (CMOS) fabrication techniques, which enables chip-scale integration and low-cost production. The sensor can be used for various applications in navigation, military, space, healthcare, and beyond.

Exploration of low-frequency broadband potential in three metamaterial configurations

Low frequency broadband is still challenging for metamaterial design. This study delves into the exploration of low-frequency broadband potential within three distinct configurations. We explore the analytic sound absorption models for Helmholtz resonators, films and locally resonant structure (membrane film with additional mass). The research investigates the capabilities and possibilities of achieving frequencies below 1000Hz for each configuration. Through a comprehensive analysis, the study aims to uncover the unique advantages and challenges associated with these three setups, shedding light on their potential applications in diverse fields. We also perform related tests for each configuration. Test results confirm the analytical models but they also highlight the benefits and drawbacks of various configurations. These findings provide valuable insights into the understanding of low-frequency broadband technology and pave the way for further advances in related areas.

Design of photonic crystals for nanokelvin-resolution thermometry

High-resolution thermometry is key for the development of calorimeters, bolometers, and high-stability light sources, as well as for probing dissipation and transport in microelectronics and quantum devices. Achieving nanokelvin-level temperature resolution at room temperature requires using large optical cavities, which are unsuitable for microscale integration. Here we computationally design a one-dimensional photonic crystal Band Edge Thermometer that achieves significant temperature sensitivity by combining: (i) the abrupt variation in optical properties of a direct bandgap semiconductor at the band edge, and (ii) a large quality factor in a resonant photonic structure. Two devices are designed which are constructed from GaAs/AlAs and GaN/AlN multilayer structures. The optimal sensor design features an extremely large thermoreflectance coefficient of 60.6 K−1 and a thermal time constant of 1.1 µs, with a sensor thickness of only 6.7 µm. The projected thermometry noise floor is 84 nK.Hz-½ for the GaAs/AlAs sensor and 35 nK.Hz-½ for the GaN/AlN sensor. The designed sensor architecture is expected to enable a broad range of applications in microcalorimetry and bolometry where a high temperature resolution combined with microscale sensor footprint is required.

Resonance Effects from Substituents on L-Type Ligands Mediate Synthetic Control of Gold Nanocluster Frontier Orbital Energies.

The ligands of metal nanoclusters can be used to control their properties and reactivity, but a framework guiding their use remains elusive. Hammett studies of Au8(PPh3)72+ and Au9(PPh3)83+ nanoclusters with para- and meta-methyl and -methoxy groups indicate that resonance effects, not inductive effects, yield quantitative shifts of the HOMO-LUMO transitions involving orbitals local to the cluster core. Individual ligand exchanges reveal that these shifts are caused by only four of seven ligands, inconsistent with inductive effects. Quantum chemical calculations predict no trend in Au atom charges with respect to Hammett parameter but do predict bond length trends expected for a resonance structure that includes the Au atoms. Computed orbitals show contributions from specific para-OMe oxygen lone pairs to the HOMO, indicating delocalization from the core to specific ligands. These results suggest that resonance structures could be drawn including Au and ligands, guiding efforts to modulate nanocluster electronic structure and energy transfer.

Structure of near-threshold resonances with new interpretation scheme of complex compositeness

The nature of near-threshold resonances is quantitatively studied with a new interpretation scheme using the complex compositeness. A difficulty was known in the understanding of the internal structure of unstable resonances because their complex compositeness is not an interpretable measure. To overcome this problem, we develop a new interpretation scheme respecting the ambiguous aspects of the identification of the internal structure of resonances. We then apply the interpretation scheme to the near-threshold resonances slightly above the threshold, described by the effective range expansion. With the new interpretation scheme, we show that near-threshold resonances are dominated by the non-molecular component. Namely, even in the near-threshold region, the nature of resonances is sharply contrasted with bound states whose internal structure is usually molecular dominant.

Synthesis and mechanistic investigation of BPA fluorescent probes targeting BPA for potential application in Boron Neutron Capture Therapy (BNCT)

Boronic acid analogs are crucial in modern organic chemistry and drug development, serving as versatile reagents and intermediates with significant therapeutic applications. This area has gained increased interest with the recent development of the drug 4-boron-L-phenylalanine (L-BPA) for boron neutron capture therapy (BNCT). Fluorescent probe technology offers an essential pathway for imaging drugs in vitro and in vivo, providing high sensitivity with great spatial and temporal resolution for both disease diagnosis and drug development. In this paper, we designed and investigated three fluorescent probes—W-1-NN, W-2-NS and W-3-NO—for sensing 4-boron-L-phenylalanine (L-BPA). Among these, only W-1-NN reacts with L-BPA, resulting in a spectral blue-shift change. This probe can “ratiometrically” and specifically detect L-BPA among various metals, with a limit of detection (LOD) of 7.11 μM. Mechanistic studies revealed that the addition of L-BPA disrupts the inherent ESIPT mechanism of W-1-NN in protonic solutions, resulting in the appearance of a new peak at 372 nm. Additionally, theoretical computational studies have also demonstrated that the complexation of W-1-NN with L-BPA triggers a change in the resonance structure, resulting in a larger energy gap and causing a blue shift in the spectrum. Furthermore, W-1-NN has been successfully applied to the detection of L-BPA in human urine. Therefore, the template probe with N/O as the target and the introduction of N atoms can specifically detect L-BPA. This template probe lays the foundation for the detection of L-BPA, and provides great possibilities for the future realization of the template probe to be connected with different fluorophores to make it emit at long wavelengths to reach the target of the near-infrared.

High selectivity wideband two‐channel bandpass filter for 5G microwave communication systems

AbstractA two‐channel high‐selectivity, wideband bandpass filter has been presented. This is based on a microstrip mixed‐impedance resonator and defected ground structure with the mixed coupling strategy. Two pairs of peripheral stepped‐impedance resonator (SIR) structures are used as stubs, achieving TZs at the immediate lower and upper cut‐off sides of the passband and control the bandwidth, while the other two transmission zeros on the upper cut‐off side are yielded through the defected ground structure, and the coupling between the SIR and uniform‐impedance resonators components, respectively. A prototype of the circuit is fabricated and measured for validation. The measured results exhibited insertion and return losses better than 1.1 and 20.5 dB, respectively, and high isolation levels exceeding 19 dB. In total, four transmission zeros are achieved. The designed filtering circuit realized a 3‐dB fractional bandwidth of 58.1%. There is a 0.95f0 stopband at the upper cutoff. The fabrication of the prototype shows good agreement between the simulated and measured performance.

Quercetin analogues of kojic acid as strong antioxidant derivatives: Theoretical insights

Kojic acid is a natural product produced by many fungal species and has a wide range of applications. The chelating and antioxidant capacity are associated with their chemical and biological properties. In this study, some molecular modifications were proposed and substituted and hydroxylated phenyl moieties were introduced in the basic structure of kojic acid. The antioxidant capacities were calculated by DFT/B3LYP/6-311++G(2d,2p). Different antioxidant mechanisms were considered such as frontier molecular orbitals (HOMO, LUMO, and GAP), electron (IP, SET, and SPLET), or hydrogen transfers (BDEOH and HAT) on gas phase and PCM methods. The phenyl increases the antioxidant capacity, especially when an electron donating group (EDG) is found at the para position of the phenyl ring when compared to electron withdrawing groups (EWGs), for all studied mechanisms. The chemical stability agrees with spin density contributions for their cationic free radicals and semiquinones. A structural similarity between hydroxylated derivatives of kojic acid and quercetin was observed on gas phase and water. The lower BDEOH values ​​at the phenol positions are more important for the antioxidant capacity than at the enol position. Phenolic semiquinones are more stables than enolic ones. The chemical stability depends on the number of resonance structures and the positions where the unpaired electron can be found with the highest contributions. In conclusion, phenyl substitution is a valuable molecular modification for the increase on antioxidant capacity of kojic acid. Quercetin analogues of kojic acid were proposed as strong antioxidant derivatives.

Ultrafast dynamics and electroluminescence performance of a novel tetraphenylethylene-based aggregation induced emission luminogen

Efficient emission and confined molecular conjugation in aggregated/solid form, are two beneficial characteristics of blue organic light-emitting materials (OLEMs). Aggregation-induced emission molecules (AIEgens) have evolved as auspicious OLEMs that possess these properties. Herein, we discover an innovative sky-blue tetraphenylethene-based AIEgen, 4′,4‴-(1-phenyl-2-(4-(1,2,2-triphenylvinyl)phenyl)-1H-imidazole-4,5-diyl)bis(N,N-diphenyl-[1,1′-biphenyl]-4-amine) (2TPA-ITPE), with high thermal stability. By employing this AIEgen as a non-doped emitter, the constructed organic light-emitting diode demonstrates a maximum external quantum efficiency of 3.35 % with a power efficiency of 4.1 lm/W and high luminescence of 15896.92 cd/m2 2TPA-ITPE exhibits a weak donor-acceptor character. Moreover, to probe the photo-physical nature of this AIEgen, its excited-state dynamics are examined through ultrafast transient absorption spectroscopy (TAS). The TAS results of this OLEM unveil the generation of a resonant structure species owing to the elongation of C=C double bond. The excited state dynamics reveal that 2TPA-ITPE undergoes three processes after excitation (internal conversion, C=C elongation and vibrational cooling). These findings offer innovative insights into the ultrafast mechanisms underlying excited TPE-based OLEMs.

Switchable SAW Resonators and Ladder Filters Composed of Interdigitated Combs.

This work presents the development of switchable surface acoustic wave (SAW) resonators fabricated on a LiNbO3 substrate, which uses the electrical Bragg bandgap concept to control the resonance frequency. The modification of the electrical condition of electrode arrays shifts their bandgap center frequency, which in turn changes the effective cavity length and resonance frequency of the resonator. This method uses the electrodes already present in SAW devices, thus reducing the complexity of potentially tunable SAW components. In this article, the electrodes that make up the cavity mirrors are connected into interdigitated comb pairs (IDCPs), reducing the necessary number of switches for operation. Finite-element method (FEM) simulations are used to analyze resonator operation and design difficulties are discussed. Frozen (with no possibility of switching) and switchable versions of a chosen resonator structure are fabricated to experimentally showcase resonator operation. It is found that it is possible to design switchable SAW resonators, which require a single switch and present a relative frequency jump of around 2.3%. Finally, frozen single-cell and four-cell ladder filters are fabricated as a proof of concept of a switchable SAW filter.

Solvatochromism, preferential solvation and excited state dipole moments of flufenamic acid in different solvent polarities

The influence of pure solvent and binary solvent mixtures on the optical properties of non-steroidal anti-inflammatory drug (NSAID) molecule, specifically flufenamic acid (FLA), has been studied using absorption and fluorescence spectroscopic techniques. A bathochromic shift is observed in the emission wavelength of FLA with an increase in the solvent polarity of pure solvents, attributed to the highest stability of the excited state. The spectral properties are correlated with Lippert–Mataga, solvent polarity parameter, Kamlet, and Catalan solvent polarity parameters, suggesting that both general and specific solvent effects influence the spectral properties, with general solvent effects dominating over specific solvent effects. Preferential solvation studies have been carried out in tetrahydrofuran (THF) and water solvent mixture, revealing variations in the preference for solvation of FLA as a function of the mole fraction of water. Solvatochromic data are utilized to estimate the excited state dipole moment in pure solvents using different solvatochromic methods, revealing that the excited state dipole moment of FLA is higher than its ground state counterpart. The increase in dipole moment in the excited state compared to the ground state is explained based on intramolecular charge transfer (ICT), with elaboration and discussion on the possible resonance structure corresponding to ICT, inferring the more polar nature of the excited state compared to the ground state. The effect of solute polarizability on the excited state dipole moment and change in dipole moment is also discussed.

Squeezing enhancement by suppression of noise through a resonant interferometric coupler

We propose an integrated resonant structure to enhance squeezing by dual-pump spontaneous four-wave mixing (SFWM) while simultaneously suppressing parametric noise due to parasitic processes. The structure relies on a resonant interferometric coupler that allows one to engineer the field enhancement on-demand in the spectral region of interest. We analyze the different configurations in which the structure can operate, and we calculate the generated squeezing. We show that our device can overcome the intrinsic squeezing limit of a single-ring resonator.

Observation of New Charmonium or Charmoniumlike States in B^{+}→D^{*±}D^{∓}K^{+} Decays.

A study of resonant structures in B^{+}→D^{*+}D^{-}K^{+} and B^{+}→D^{*-}D^{+}K^{+} decays is performed, using proton-proton collision data at center-of-mass energies of sqrt[s]=7, 8, and 13TeV recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb^{-1}. A simultaneous amplitude fit is performed to the two channels with contributions from resonances decaying to D^{*-}D^{+} and D^{*+}D^{-} states linked by C parity. This procedure allows the C parities of resonances in the D^{*±}D^{∓} mass spectra to be determined. Four charmonium or charmoniumlike states are observed decaying into D^{*±}D^{∓}: η_{c}(3945), h_{c}(4000), χ_{c1}(4010), and h_{c}(4300), with quantum numbers J^{PC} equal to 0^{-+}, 1^{+-}, 1^{++}, and 1^{+-}, respectively. At least three of these states have not been observed previously. In addition, the existence of the T_{c[over ¯]s[over ¯]0}^{*}(2870)^{0} and T_{c[over ¯]s[over ¯]1}^{*}(2900)^{0} resonances in the D^{-}K^{+} mass spectrum, already observed in the B^{+}→D^{+}D^{-}K^{+} decay, is confirmed in a different production channel.