Enhanced Coupling Efficiency Research Articles

Simulation and measurement of electromagnetic wave propagations along a wearable e-textile metasurface transmission line

This study introduces a compact wearable metasurface transmission line operating at 2.45 GHz, utilizing spoof surface plasmon polariton (SSPP). The design incorporates a periodic arrangement of hook unit cells and a tapering structure to enhance coupling efficiency between the microstrip feed line and the metasurface transmission line. For its implementation, a dielectric substrate composed entirely of cotton denim jeans is employed, along with e-textile conductive traces and a ground plane. Electromagnetic wave propagation along the transmission line is simulated, and the primary wave mode and associated propagation characteristics are analyzed. Both simulation and measurement results confirm the successful performance of the metasurface transmission line for on-body signal transmissions.

Formation and mechanical properties of AZ31B magnesium alloy welds by power-modulated oscillating laser

an energy-space modulated laser was proposed in welding workpieces with AZ31B magnesium alloy to enhance the efficiency of heat transfer and reduce defects of welds, and the proposed laser was power-modulated oscillating laser (PMOL). To validate the performance of the proposed technique, non-penetration welding and butt welding were conducted on the workpieces with a thickness of 5 mm. The impact of power-modulation parameters was investigated at the aspects of micro-structures, appearance, and mechanical properties of welds. The results showed that in comparison with a conventional laser (CL) or circular oscillation laser (COL), an energy-space modulated laser led to (1) an increased depth of weld penetration and (2) an enhanced coupling efficiency of laser energy. The parameters of power modulation could be optimized to reduce the defects of welds such as spatter, underfill, and thick fish scales significantly reduced; it refined the equiaxed grains in the center area of weld. When the frequency and amplitude of power-modulation were set as 50 Hz and 500 W, respectively, the mechanical properties of the weld were improved with the ultimate tensile strength of 238 MPa and an elongation ratio of 13.9 % which were 96.1 % and 58.7 % of those of the base material (BM), respectively. In comparison with the results welded by CL and COL, the ultimate tensile strength by PMOL was increased by 13.9 % and 4.4 %, and the elongation was increased by 54.4 % and 8.6 %, respectively.

Engineered Core-Shell Multifunctional Nano-Tracer in Raman-Silent Region with Highly Retained Affinity to Enhance Lateral Flow Immunoassays.

Stimulated surface-enhanced Raman scattering (SERS) in combination with engineered nano-tracer offers extraordinary potential in lateral flow immunoassays (LFIAs). Nonetheless, the investigation execution of SERS-LFIA is often compromised by the intricacy and overlap of the Raman fingerprint spectrum as well as the affinity-interference of nano-tracer to antibody. To circumvent these critical issues, an engineered core-shell multifunctional nano-tracer (named APNPs) with precise control of the size of nano-core (AuNPs) and coating of the nano-shell (Prussian blue nanomaterials) is prepared for SERS-LFIA via a modified enlarging particle size and coating modification strategy. Importantly, this nano-tracer exhibits enhanced coupling efficiency, highly retained affinity, reinforced colloid stability, and unique SERS signal (2156 cm-1 ) in the silent region (1800-2800 cm-1 ) with high signal-to-background ratio simultaneously, all of which are beneficial to the enhancement of the analysis performance. With a proof-of-concept demonstration for detection of ractopamine (RAC), a dual-pattern LFIA that synergizes both the enlarged particle size and coating modification supported colorimetric/biological silence Raman dual-response (coined as the ECCRD assay) is demonstrated by integrating APNPs with the competitive-type immunoreaction. This research may contribute to the rational design of multifunctional nano-tracer, and the ECCRD assay can be expanded for a wide spectrum of applications in environmental monitoring and biomedical diagnosis.

Enhanced coupling efficiency in metal – dielectric – metal waveguide-ring structure for plasmonic temperature sensor and sucrose concentration detector

In this paper, we propose a sensing structure based on metal-dielectric-metal waveguide technology, which comprises of two square ring resonators side linked to the bus waveguide and operates in the infrared and near infrared regions. The results revealed that the proposed device enormously enhanced the coupling effect between the main waveguide and the cavity thereby increasing the sensor's performance parameters. The device has an ability to act as refractive index sensor, temperature sensor for ethanol and sucrose concentration detector with sensitivities of 2880 nm/RIU, 1.375 nm/℃, and 1750 nm/RIU, respectively. The device is also optimized by changing the structural parameters and material medium. The sensor design is simple to construct, has better sensing features, and is small in size. Thus, the proposed plasmonic sensor is relevant for lab-on-chip gas and biochemical detection (having an optical refractive index between 1.0 and 1.5).

Optical Feedback Linear Cavity Ringdown Spectroscopy

Optical feedback cavity ringdown spectroscopy is presented with a linear Fabry–Pérot cavity and a cost-effective DFB laser. To circumvent the low coupling efficiency caused by the broad laser linewidth, an optical feedback technique is used, and an enhanced coupling efficiency of 31%, mainly limited by impedance mismatch and mode mismatch, is obtained. The trigger of the ringdown event is realized by the shutoff of the laser driving current, and a novel method with the aid of one electronic switch is applied to avoid the ringdown events excited by the unexpected cavity modes during the process of laser current recovery. As a result, the ringdown signal with a signal-to-noise ratio of 2500 is achieved. Through continuous monitoring, the fractional uncertainty of the empty cavity ringdown times is assessed to be 0.04%. An Allan variance analysis indicates a detection sensitivity of 4.3 × 10−10 cm−1 is resulted at an integration time of 120 s, even with a moderate finesse cavity. To further improve the long-term stability, we regularly rectify the empty cavity ringdown time, and an improvement factor of 2.5 is demonstrated.

Two-photon-polymerization enabled and enhanced multi-channel fibre switch

This article discusses the fabrication and performance of a multi-channel fibre switch, consisting of 19 single-mode fibres, with enhanced coupling efficiency due to micro-optics, directly printed via two-photon-polymerization on the end-face of each fibre. The use of high-resolution two-photon-polymerization not only allows the enhancement of the coupling efficiency with respect to the coupling device in use but likewise offers great freedom in the arrangement of the used fibres. This letter gives a thorough explanation of the fabrication method as well as the optical simulations for the lenses on the fibre assembly.

Small-Size Coaxial Resonant Applicator for Microwave Heating Assisted Additive Manufacturing

This article introduces the design and analysis of a small-size coaxial resonant applicator for high-speed microwave heating-assisted additive manufacturing of multiple materials, such as continuous carbon fiber reinforced polymer composites, thermoplastic, and metal parts. The elaborated coaxial resonant applicator reduces the size and has a resonant frequency between 2.4 and 2.5 GHz. A TEM wave is stimulated in the applicator where the electrical field is polarized perpendicular to the filaments and, therefore, allows a maximum penetration depth. The electrical conductive filament is designed as a part of the inner conductor to enhance coupling efficiency. To prevent microwave leakage induced by the conductive material, a compact quarter wavelength filter was developed. The equivalent circuit of the filter was used to analyze the influence of structural parameters on the resonance frequency. The filter has been tested and good agreement between measured and simulated results is obtained. The heating behavior with varying input power has been investigated for polyamide, polylactic acid, and continuous carbon fiber reinforced polyamide filaments.

Reflection based coupling efficiency enhancement in a fluorescent planar concentrator for an optical wireless receiver.

Fluorescent planar concentrators have been proposed as optical concentrators that can have both a wide field of view and a high optical gain stemming from a large collection area for optical wireless communications. However, the fluorescent concentrators with such a large collection area often lead to a low light coupling efficiency due to the edge coupling mechanism leading to a considerable optical power loss. In this work, an analysis of the light coupling efficiency enhancement in the electrical power gain is presented. In particular, a practical method to improve the coupling efficiency by introducing edge and back reflection using Lambertian-, specular-, and retro-reflectors is presented. It is demonstrated that by choosing the optimal reflectors, the received signal strength can be improved by more than a factor of two. Also demonstrated with the proposed method is a data rate more than 1.12 Gbps with bit error rate less than 3.8 × 10-3 using a DC-biased optical orthogonal frequency division multiplexing. This is, to the best of our knowledge, the first Gbps class demonstration using a commercial fluorescent planar concentrator.

Enhanced coupling efficiency and electrical property in surface plasmon-enhanced light-emitting diodes with the tapered Ag structure.

We design, fabricate and analyze plasmon-enhanced LEDs with the tapered Ag structure that significantly increases plasmonic coupling efficiency at a coupling distance far beyond the penetration depth. The electroluminescence intensity showed a 16-fold increase compared with planar LEDs with a coupling distance of 100 nm. The enhanced coupling efficiency with large distance is originated from the accumulated SP energy at the metal conical tip and the missing momentum provided by the corrugated surface. Therefore, the SP-enhanced LED with tapered Ag structure can maintain a high luminous efficiency and a stable working state even with thick p-GaN layer, which also guarantees a high electrical performance. Our study paves the way for a practical implementation of SP-enhanced LEDs with excellent optical and electrical properties.

OxymaPure Coupling Reagents: Beyond Solid-Phase Peptide Synthesis

AbstractOxymaPure [ethyl 2-cyano-2-(hydroxyimino)acetate] is an exceptional reagent with which to suppress racemization and enhance coupling efficiency during amide bond formation. The tremendous popularity of OxymaPure has led to the development of several Oxyma-based reagents. OxymaPure and its derived reagents are widely used in solid- and solution-phase peptide chemistry. This review summarizes the recent developments and applications of OxymaPure and Oxyma-based reagents in peptide chemistry, in particular in solution-phase chemistry. Moreover, the side reaction associated with OxymaPure is also discussed.1 Introduction2 Oxyma-Based Coupling Reagents2.1 Aminium/Uronium Salts of OxymaPure2.2 Phosphonium Salts of OxymaPure2.3 Oxyma-Based Phosphates2.4 Sulfonate Esters of OxymaPure2.5 Benzoate Esters of OxymaPure2.6 Carbonates of OxymaPure Derivatives3 OxymaPure Derivatives4 Other Oxime-Based Additives and Coupling Reagents5 Side Reactions Using OxymaPure Derivatives6 Conclusion7 List of Abbreviations

Broadband High-Efficiency Grating Couplers for Perfectly Vertical Fiber-to-Chip Coupling Enhanced by Fabry-Perot-like Cavity.

We propose a broadband high-efficiency grating coupler for perfectly vertical fiber-to-chip coupling. The up-reflection is reduced, hence enhanced coupling efficiency is achieved with the help of a Fabry-Perot-like cavity composed of a silicon nitride reflector and the grating itself. With the theory of the Fabry-Perot cavity, the dimensional parameters of the coupler are investigated. With the optimized parameters, up-reflection in the C-band is reduced from 10.6% to 5%, resulting in an enhanced coupling efficiency of 80.3%, with a 1-dB bandwidth of 58 nm, which covers the entire C-band. The minimum feature size of the proposed structure is over 219 nm, which makes our design easy to fabricate through 248 nm deep-UV lithography, and lowers the fabrication cost. The proposed design has potential in efficient and fabrication-tolerant interfacing applications, between off-chip light sources and integrated chips that can be mass-produced.

Mesozooplankton biomass and temperature-enhanced grazing along a 110°E transect in the eastern Indian Ocean

Low-latitude waters of the Indian Ocean are warming faster than other major oceans. Most models predict a zooplankton decline due to lower productivity, enhanced metabolism and phytoplankton size shifts that reduce trophic transfer efficiency. In May-June 2019, we investigated mesozooplankton biomass and grazing along the historic 110°E transect line from the International Indian Ocean Expedition (IIOE) of the 1960s. Twenty sampling stations from 39.5 to 11.5°S spanned latitudinal variability from temperate to tropical waters and a pronounced 14°C gradient in mean euphotic zone temperature. Although mesozooplankton size structure was similar along the transect, with smaller (<2 mm) size classes dominant, total biomass increased 3-fold (400 to 1500 mg dry weight m-2) from high to low latitude. More dramatically, gut-fluorescence estimates of grazing (total ingestion or % euphotic zone chl a consumed d-1) were 14- and 20-fold higher, respectively, in the low-latitude warmer waters. Biomass-normalized grazing rates varied more than 6-fold over the transect, showing a strong temperature relationship (r2 = 0.85) that exceeded the temperature effects on gut turnover and metabolic rates. Herbivory contributed more to satisfying zooplankton energetic requirements in low-chl a tropical waters than chl a-rich waters at higher latitude. Our unexpected results are inconsistent with trophic amplification of warming effects on phytoplankton to zooplankton, but might be explained by enhanced coupling efficiency via mixotrophy. Additional implications for selective herbivory and top-down grazing control underscore the need for rigorous field studies to understand relationships and validate assumptions about climate change effects on the food webs of tropical oceans.

Investigation and optimization of light trapping through hexagonal-shaped nanopillar (NP) array of indium gallium arsenide material based photodetector

Nanopillar arrays over the photodetector’s surface attribute an enhanced coupling efficiency of incident light due to its various light trapping mechanisms that contribute towards high-resolution optical detection. This paper reports the analytical investigation of the performance of Indium Gallium Arsenide material based hexagonal-shaped nanopillar (NP) array deployed over the 5 um × 5 um detector’s front surface for high photodetection infrared applications. The proposed structure exhibits an optimum 98% overall absorption of the incoming light. High EQE of about 75% and responsivity of 0.93 A/W has been obtained at 1.55 um operating wavelength with a minimum detector’s depletion width of 0.7 um at 1 mw optical input power.

Bowtie loaded meander antenna for a high-temperature superconducting terahertz detector and its characterization by the Josephson effect.

In a quasi-optical system, the high temperature superconducting terahertz detector often suffers from a fundamental problem of low coupling efficiency with the terahertz signal, especially for the detector based on YBa2Cu3O7-δ (YBCO) bicrystal Josephson junction (JJ) due to a small normal-state resistance. Here, we developed a bowtie loaded meander antenna to enhance coupling efficiency. Differing from the conventional characterization confining on vector network analyzers, we applied three methods to evaluate the antenna, including the measurements of the maximal size of the first order Shapiro step under per incident power, the coupling efficiency between the antenna and the junction, and voltage responsivity. Furthermore, with simulation analysis, we propose that the inductive reactance of the YBCO bicrystal JJ is around 60 ohms under terahertz irradiation at 210 GHz, thus, the reactance is comparable as that of the antenna.

Efficient polymer waveguide grating coupler with directionality enhancement

Polymer is viewed as an ideal platform for integrated photonics sensing. We propose a polymer waveguide grating coupler with the enhancement of directionality. A gold film mirror beneath the grating coupler is introduced to prevent the power leakage into the substrate. A Bragg grating reflector in series with the coupler is adopted to reverse the forward diffraction light. The finite-difference time-domain method is used to theoretically investigate the dimensional parameters of grating coupler, gold film mirror, as well as the grating reflector. With both two methods, an enhanced coupling efficiency of 51.31 % can be obtained at the wavelength of 1550 nm. The 62-nm wide 1-dB bandwidth covers the C-band. The proposed design has potentials in integrated optical circuit and monolithic integrated sensors.

Free-space coupling enhancement of micro-resonators via self-accelerating beams.

We study free-space coupling of optical fields to the whispering-gallery-mode resonators by employing self-accelerating beams orbiting a semicircle. The best coupling condition is obtained through theoretical analysis, in accord with the numerical results. Comparing with the conventional Gaussian-like beams, much enhanced coupling efficiency is achieved with such self-accelerating beams, particularly when a large numerical aperture of an optical system is used or a higher-order azimuthal mode is considered. Conditions with slight deviation from the ideal radius of self-accelerating beams are further discussed, aiming to realize an optimized high coupling efficiency.

Design and Optimization of Open-cladded Plasmonic Waveguides for CMOS Integration on Si3N4 Platform

Herein, we present a design analysis and optimization of open-cladded plasmonic waveguides on a Si3N4 photonic waveguide platform targeting CMOS-compatible manufacturing. For this purpose, two design approaches have been followed aiming to efficiently transfer light from the hosting photonic platform to the plasmonic waveguide and vice versa: (i) an in-plane, end-fire coupling configuration based on a thin-film plasmonic structure and (ii) an out-of-plane directional coupling scheme based on a hybrid slot waveguide. A comprehensive numerical study has been conducted, initially deploying gold as the reference metal material for validating the numerical models with already published experimental results, and then aluminum and copper have been investigated for CMOS manufacturing revealing similar performance. To further enhance coupling efficiency from the photonic to the plasmonic part, implementation of plasmonic tapering schemes was examined. After thorough investigation, plasmo-photonic structures with coupling losses per single interface in the order of 1 dB or even in the sub-dB level are proposed, which additionally exhibit increased tolerance to deviations of critical geometrical parameters and enable CMOS-compatible manufacturing.

Dynamics simulation and experiment of smooth end face grinding on photonic crystal fiber.

A smooth end face is the critical factor for the application of photonic crystal fiber (PCF) to enhance coupling efficiency. A number of air holes distributed on the cladding make the surface a discontinuous structure. For the sake of acquiring a high-quality end surface of PCF, this paper proposes a detailed study first on dynamics simulation of the grinding process of PCF using a finite element model with a verification experiment later. To facilitate the calculation, the grinding is simplified as a single grain to cut the material on the location between two holes. The process of material removal is analyzed on the basis of force curve obtained by changing the cutting depth and position, respectively. Theoretical and experimental results illustrate that the earliest material collapse occurs on the rim of the air hole, and brittle cracks extend along circumferential and axial direction of the hole; the damage on the edge of the hole is more severe with the increment of grain tip radius and cutting depth. Keeping the grinding force stable can achieve the process in the ductile regime, and a smooth surface can be obtained by polishing with abrasive paper of fine grit.

Functional molecular complexes of junctophilin‐2 and caveolin‐1 provide a structural/functional basis for Ca2+‐microdomain formation between BKCa channels and RyRs in vascular smooth muscle cells

Functional coupling between large-conductance Ca2+-activated K+ (BKCa) channels in plasma membrane (PM) and ryanodine receptors (RyRs) in sarcoplasmic reticulum (SR) is an essential mechanism for mechanical force regulation in smooth muscle cells (SMCs). Spontaneous Ca2+ release through RyRs (knows as Ca2+ sparks) and subsequent BKCa channels activation detected as spontaneous transient outward currents (STOCs) occur within PM-SR junctional sites, often called Ca2+ microdomains. We have previously reported that Caveolae, W-shaped invaginations of PM, accumulate BKCa channels within the structure and enhance coupling efficiency between Ca2+ sparks and BKCa channels/STOC activity in mouse mesenteric artery SMCs (mMASMCs). However, the molecular basis between caveolae and RyRs in SR membrane is unclear. In the present study, we demonstrated that both caveolin-1 (Cav1), a caveola forming protein, and junctophilin-2 (JP2), a bridging protein between PM and SR, reciprocally contribute to Ca2+microdomain formation. Co-immunoprecipitation using rat mesenteric arterial tissues and double-immunocytochemical staining analyses by total internal reflection fluorescent microscopy revealed the direct interaction between JP2 and Cav1. Mouse mesenteric arterial tissues were organ-cultured and concomitantly treated with siRNA using reversible permeabilization procedures. Knockdown of JP2 in mMASMCs significantly decreased the colocalization of Cav1 and RyRs and the amplitude of STOCs. The contraction induced by the inhibition of BKCa channels/STOC activity and subsequent membrane depolarization in siJP2-treated mMASMCs was significantly smaller than that in siControl. These results suggested that the novel interaction of JP2 with Cav1 seems to provide a structural/functional basis for Ca2+-mediated crosstalk between RyRs and BKCa channels, and likely positions the PM-SR junctional sites to convert Ca2+ spark signals into hyperpolarizing signals in SMCs lacking transverse tubular system. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Nanophotonic Ultrashort Coupler Based on Hybrid Plasmonic Waveguide With Lateral Subwavelength Grating

A nanophotonic vertical coupler with ultrashort coupling length based on hybrid plasmonic (HP) waveguide with a lateral subwavelength grating (LSG) is proposed. An ultrashort coupling length of 0.461 μ m is achieved through the lateral resonances in the subwavelength grating. The combined effect of LSG and the metal layer sandwiched between the coupling dielectric-regions makes it possible to realize efficient coupling and low-loss guiding of hybrid modes with a propagation lengths of 123 and 53 μm, respectively, for odd and even modes. The vertical coupling influenced by the lateral resonances through LSG also exhibits broadband nature where the coupling length remains acceptably small and the coupling performance remains high over a broad range of wavelengths. The coupling performance of 192 and a low propagation loss of 0.035 dB/μm are reported with the analysis based on finite element method. LSG introduced into the HP waveguide is shown to provide multifold benefits of increased fabrication tolerance, enhanced coupling efficiency and expanded coupling regime.