Strong Near-field Enhancement Research Articles

Relations between near-field enhancements and Purcell factors in hybrid nanostructures of plasmonic antennas and dielectric cavities

Strong near-field enhancements (NFEs) of nanophotonic structures are believed to be closely related to high Purcell factors (FP). Here, we theoretically show that the correlation is partially correct; the extinction cross section (σ) response is also critical in determining FP. The divergence between NFE and FP is especially pronounced in plasmonic-dielectric hybrid systems, where the plasmonic antenna supports dipolar plasmon modes and the dielectric cavity hosts Mie-like resonances. The cavity's enhanced-field environment can boost the antenna's NFEs, but the FP is not increased concurrently due to the larger effective σ that is intrinsic to the FP calculations. Interestingly, the peak FP for the coupled system can be predicted by using the NFE and σ responses. Furthermore, the limits for FP of coupled systems are considered; they are determined by the sum of the FP of a redshifted (or modified, if applicable) antenna and an individual cavity. This contrasts starkly with the behavior of NFE which is closely associated with the multiplicative effects of the NFEs provided by the antenna and the dielectric cavity. The differing behaviors of NFE and FP in hybrid cavities have varied impacts on relevant nanophotonic applications such as fluorescence, Raman scattering and enhanced light-matter interactions.

Indefinite metacavities coupled to a mirror: bound states in the continuum with anomalous resonance scaling

Indefinite metacavities (IMCs) made of hyperbolic metamaterials show great advantages in terms of extremely small mode volume due to large wave vectors endowed by the unique hyperbolic dispersion. However, quality (Q) factors of IMCs are limited by Ohmic loss of metals and radiative loss of leaked waves. Despite the fact that Ohmic loss of metals is inevitable in IMCs, the radiative loss can be further suppressed by leakage engineering. Here we propose a mirror coupled IMC structure which is able to operate at Fabry–Pérot bound states in the continuum (BICs) while the hyperbolic nature of IMCs is retained. At the BIC point, the radiative loss of magnetic dipolar cavity modes in IMCs is completely absent, resulting in a considerably increased Q factor (>90). Deviating from the BIC point, perfect absorption bands (>0.99) along with a strong near-field intensity enhancement (>1.8×104) appear when the condition of critical coupling is almost fulfilled. The proposed BICs are robust to the geometry and material composition of IMCs and anomalous scaling law of resonance is verified during the tuning of optical responses. We also demonstrate that the Purcell effect of the structure can be significantly improved under BIC and quasi-BIC regimes due to the further enhanced Q factor to mode volume ratio. Our results provide a new train of thought to design ultra-small optical nanocavities that may find many applications benefitting from strong light–matter interactions.

Dynamic Spectral Modulation Enabled by Conductive Polymer-Integrated Plasmonic Nanodisk-Hole Arrays.

The electrically driven optical performance modulation of the plasmonic nanostructure by conductive polymers provides a prospective technology for miniaturized and integrated active optoelectronic devices. These features of wafer-scale and flexible preparation, a wide spectrum adjustment range, and excellent electric cycling stability are critical to the practical applications of dynamic plasmonic components. Herein, we have demonstrated a large-scale and flexible active plasmonic nanostructure constructed by electrochemically synthesizing nanometric-thickness conductive polymer onto spatially mismatched Au nanodisk-hole (AuND-H) array on the poly(ethylene terephthalate) (PET) substrate, offering low-power electrically driven switching of reflective light in a wide wavelength range of 550-850 nm. The composite structure of the polymer/AuND-H array supports multiple plasmonic resonance modes with strong near-field enhancement and confinement, which provides an excellent dynamic spectral modulation platform. As a result, the PPy/AuND-H array achieves 18.4% reversible switching of spectral intensity at 780 nm and speedy response time, as well as maintains a stable dynamic modulation range at two-potential cycling between -0.6 and 0.1 V after 200 modulation cycles. Compared to the case of the PPy/AuND-H array, the PANI/AuND-H array obtains a more extensive intensity modulation of 25.1% at 750 nm, which is attributed to the significant differences in the extinction coefficient between the oxidized and reduced states of PANI, but its modulation range degrades apparently after 20 cycles driven at applied voltages between -0.1 and 0.8 V. Additionally, the cycling stability could be further improved by reducing the modulation voltage range. Our proposed electromodulated composite structure provides a promising technological proposal for dynamically plasmonic reconfigurable devices.

Quantitative analysis of circular dichroism at higher-order resonance of extrinsic plasmonic chiral nanostructures using multipole decomposition combined with the optical theorem

Plasmonic chirality, which has garnered significant attention in recent years due to its ability to generate strong near-field enhancement and giant circular dichroism (CD). Currently, various theories have been proposed to explain plasmonic extrinsic chirality, however, a comprehensively quantitative explanation for the high-order optical response of extrinsic metamolecule has yet to be established. Herein, we present a concise and quantitative explanation of the giant high-order extrinsic CD of a plasmonic nanocrescent, which origins from multipole decomposition in combination with the optical theorem. Our findings indicate that the high-order resonance modes exhibit giant CD comparable to dipolar modes and can be conveniently applied to the chiral recognition of metamolecules. Furthermore, the nonradiative electric quadrupole resonance exhibits enormous electric field enhancement near metamolecule, which has great application potential in the fields of molecular recognition and sensing in the visible region.

Boosting multi-mode strong coupling in a hybrid vertical split-ring resonator metamaterial for magnetoplasmonic sensing

Achieving multi-mode strong coupling between different modes in nanoscale is challenging due to the large damping rate of the system. Here, we report an effective way to achieve multi-mode plasmonic and magnetic resonances strong coupling via introducing the localized surface plasmon resonance into the designed dimer vertical split-ring resonator (DVSRR) magnetoplasmonic metamaterial. Due to strong near-field enhancement and far-field scattering suppression, the Rabi splitting energy could be enhanced from 144 meV to 286 meV. Benefiting from the multi-mode strong coupling, three distinct Kerr reversals are obtained in the Kerr spectrum, which provides a feasible route for achieving multi-mode magnetoplasmon-sensor, with high FoM of 4265/RIU, 135/RIU and 3995/RIU, respectively. The hybrid branches are analyzed with weighting coefficients that are calculated by the three coupled oscillator model.

Trapping and sorting of nanoparticles by bowtie-nanohole plasmonic tweezers

Optical tweezers are a crucial tool for manipulating nanoscale objects, and have a wide range of applications in various fields. Bowtie-nanohole tweezers, a type of near-field optical tweezers, are particularly intriguing due to their strong near-field enhancement and unique characteristics. In this paper we provide a detailed discussion of the properties of bowtie-nanohole tweezers on trapping and sorting nanoparticles through theoretical and numerical results. It is discovered that the tweezers behave differently when trapping particles with varying refractive indices, leading to a discussion of sorting chiral particles. Moreover, the relative refractive index between the particles and the background solution greatly influences the trapping and sorting abilities of the tweezers. Finally, we investigate the performance of the tweezers at different wavelengths of incident light to determine the optimal working wavelength for trapping or sorting.

Modified bow-tie antenna array with efficient electric near-field enhancement for terahertz band

Antenna arrays can induce strong electric near-field enhancement to improve the performance of biological imaging resolution, macromolecule detection sensitivity, and sensing accuracy. However, the use of antenna arrays to regulate both the electric near-field enhancement factor and area has rarely been reported. In this paper, a novel modified bow-tie (MBT) antenna array is proposed for better near-field enhancement performance in terahertz (THz) regime. Using commercially available high frequency structure simulator (HFSS), the dimensions of the MBT antenna array, including gap width, arm length, array period, and substrate thickness, are optimized to improve electric near-field enhancement performance in terms of higher factor, larger area, more controllable peak frequency, and wider 1-dB bandwidth. The as-optimized MBT and bow-tie (BT) THz antenna arrays are fabricated on quartz substrate via lithography and lift-off process. The normalized transmittances of the MBT and BT antenna arrays are characterized by THz time-domain spectroscopy (THz-TDS) and compared with the corresponding simulated near-field enhancement factor and normalized transmittance. The results indicate that the MBT antenna array outperforms the BT antenna array with a three-fold increase in near-field enhancement area and a 66.7% wider 1-dB bandwidth, and therefore can be used to enhance detection sensitivity and sensing accuracy in weak terahertz environment.

Hierarchically Doped Plasmonic Nanocrystal Metamaterials.

Assembling plasmonic nanocrystals in regular superlattices can produce effective optical properties not found in homogeneous materials. However, the range of these metamaterial properties is limited when a single nanocrystal composition is selected for the constituent meta-atoms. Here, we show how continuously varying doping at two length scales, the atomic and nanocrystal scales, enables tuning of both the frequency and bandwidth of the collective plasmon resonance in nanocrystal-based metasurfaces, while these features are inextricably linked in single-component superlattices. Varying the mixing ratio of indium tin oxide nanocrystals with different dopant concentrations, we use large-scale simulations to predict the emergence of a broad infrared spectral region with near-zero permittivity. Experimentally, tunable reflectance and absorption bands are observed, owing to in- and out-of-plane collective resonances. These spectral features and the predicted strong near-field enhancement establish this multiscale doping strategy as a powerful new approach to designing metamaterials for optical applications.

Manifold enhancement in the near-field and SERS efficiency of all-sputter grown Ag-nanoparticles on Al-film based mirror structures

Gap mode plasmonic coupling of noble metal nanoparticles with metal films makes them ideal candidates for manifold improvement in the surface-enhanced Raman scattering (SERS) efficacy via strong near-field enhancement in their gap realized by deposition of sandwiched dielectric spacer layers. This report presents an all-sputtering grown SERS substrate based on gap mode plasmonic coupling of Ag-NPs with Al films separated with thin dielectric overlayers of AlOx or polytetrafluoroethylene (PTFE). A remarkably high Analytical enhancement factor (as high as 3.7 × 109) with manifold SERS enhancement (as high as 26 times) is obtained with a limit of detection up to 10−13 M concentration of CV dye. Growth of thin dielectric over layer remains conformal on randomly orientated hillocks-like Al nanocrystallites (NCs) on Si substrates. Reflection studies show the broadband absorption of gap plasmon mode coupled Ag nanoparticles (NPs) and Al films. An optical model constructed using generalized oscillator model with the help of Lorentz and Tauc-Lorentz oscillators which reveals the localized surface plasmon resonance (LSPR) of Ag-NPs is strongly enhanced after gap mode plasmonic coupling (GMPC) in Ag-NPs and Al film based nanoparticles-on-mirror (NPoM) system. Finite difference time domain (FDTD) simulations validate the experimental findings that NPoM structure results in GMPC between Ag-NPs and underlying Al films. This study paves a way towards NPoM-based manifold enhancement in SERS-based detection efficacy of ultralow concentration of complex molecules.

Plasmonically coupled semiconductor quantum dots for efficient hydrogen photoelectrocatalysis

Photocatalytic water splitting has attracted significant attention as a low-cost, clean, and green method for the conversion of solar energy into hydrogen, highlighting its potential to solve energy and environmental problems. In this work, we report the coupling of a plasmonic resonator with semiconductor quantum dots (QDs) for enhancement in photoelectrocatalytic water splitting toward hydrogen (H2) production. Specifically, cadmium selenide (CdSe) QDs were deposited on silver nano-gratings (Ag gratings). Plasmonic enhancement was observed in the absorption/emission of QDs using our angle-resolved steady-state optical spectroscopy. Furthermore, angle-resolved absorption spectra helped us to optimize the illumination conditions for resonant excitation using a setup for photoelectrochemical (PEC) experiments. Under the resonant pump, the emission of the QDs has been plasmonically enhanced with a Purcell factor (FP) of ∼1.5. Our numerical simulation revealed a strong near-field enhancement due to the excitation of surface plasmon resonances, contributing to FP. A similar enhancement order in the PEC experiments was also observed under resonant pump conditions, indicating the contribution of plasmon resonances to the enhanced photoelectrocatalysis. Switching the excitation's polarization further reinforces this, resulting in an enhanced photocurrent under p-polarization. These findings provide a proof of concept, thus laying the foundation for a practical device for efficient solar-to-H2 conversion.

Anapole-assisted ultra-narrow-band lattice resonance in slotted silicon nanodisk arrays

Anapole modes supported by well-designed dielectric nanostructures have attracted extensive attention in the field of nanophotonic applications owing to their unique strong near-field enhancement and non-radiative far-field scattering characteristics, yet it is still difficult to achieve high Q-factor resonance features with a narrow linewidth. In this work, a periodic slotted silicon nanodisk array is theoretically proposed to realize narrow linewidth and high Q-factor resonance in the near-infrared wavelength range. Through introducing the coupling between the anapole modes in the single dielectric nanostructure and the diffractive wave mode arising from the periodic array, the as-designed dielectric nanostructure synchronously manifests excellent spectral features with a bandwidth as narrow as about 2.0 nm, a large Q-factor of 599, an almost-perfect transmission amplitude of 96% and a relatively high electric field intensity (>2809 times) in the middle of the slotted silicon nanodisk. The as-designed nanostructure possessing these outstanding optical features can work as a high-efficiency refractive index sensor, whose sensitivity can reach 161.5 nm RIU−1 with its figure of merit attaining 80.8 RIU−1, efficiently distinguishing an index change of less than 0.01. The proposed slotted silicon nanodisk array exhibits tremendous potential for expanding applications such as label-free biochemical sensing, plasmonic refractive index sensing and surface enhancement spectroscopy.

Ultrasensitive Terahertz Biodetection Enabled by Quasi-BIC-Based Metasensors.

Advanced sensing devices, highly sensitive, and reliable in detecting ultralow concentrations of circulating biomarkers, are extremely desirable and hold great promise for early diagnostics and real-time progression monitoring of diseases. Nowadays, the most commonly used clinical methods for diagnosing biomarkers suffer from complicated procedures and being time consumption. Here, a chip-based portable ultra-sensitive THz metasensor is reported by exploring quasi-bound states in the continuum (quasi-BICs) and demonstrate its capability for sensing low-concentration analytes. The designed metasensor is made of the designed split-ring resonator metasurface which supports magnetic dipole quasi-BIC combining functionalized gold nanoparticles (AuNPs) conjugated with the specific antibody. Attributed to the strong near-field enhancement near the surface of the microstructure enabled by the quasi-BICs, light-analyte interactions are greatly enhanced, and thus the device's sensitivity is boosted significantly. The system sensitivity slope is up to 674 GHz/RIU, allowing for repeatable resolving detecting ultralow concentration of C-reactive protein (CRP) and Serum Amyloid A (SAA), respectively, down to 1 pM. The results touch a range that cannot be achieved by ordinary immunological assays alone, offering a novel non-destructive and rapid trace measured approach for next-generation biomedical quantitative detectionsystems.

Synergistic Photon Management and Strain-Induced Band Gap Engineering of Two-Dimensional MoS2 Using Semimetal Composite Nanostructures

2D MoS2 attracts increasing attention for its application in flexible electronics and photonic devices. For 2D material optoelectronic devices, the light absorption of the molecularly thin 2D absorber would be one of the key limiting factors in device efficiency, and conventional photon management techniques are not necessarily compatible with them. In this study, we show two semimetal composite nanostructures deposited on 2D MoS2 for synergistic photon management and strain-induced band gap engineering: (1) the pseudo-periodic Sn nanodots, (2) the conductive SnOx (x < 1) core-shell nanoneedle structures. Without sophisticated nanolithography, both nanostructures are self-assembled from physical vapor deposition. Optical absorption enhancement spans from the visible to the near-infrared regime. 2D MoS2 achieves >8× optical absorption enhancement at λ = 700-940 nm and 3-4× at λ = 500-660 nm under Sn nanodots, and 20-30× at λ = 700-900 nm under SnOx (x < 1) nanoneedles. The enhanced absorption in MoS2 results from strong near-field enhancement and reduced MoS2 band gap due to the tensile strain induced by the Sn nanostructures, as confirmed by Raman and photoluminescence spectroscopy. Especially, we demonstrate that up to 3.5% biaxial tensile strain is introduced to 2D MoS2 using conductive nanoneedle-structured SnOx (x < 1), which reduces the band gap by ∼0.35 eV to further enhance light absorption at longer wavelengths. To the best of our knowledge, this is the first demonstration of a synergistic triple-functional photon management, stressor, and conductive electrode layer on 2D MoS2. Such synergistic photon management and band gap engineering approach for extended spectral response can be further applied to other 2D materials for future 2D photonic devices.

Photonic-Plasmonic Coupling Enhanced Fluorescence Enabling Digital-Resolution Ultrasensitive Protein Detection.

Assays utilizing fluorophores are common throughout life science research and diagnostics, although detection limits are generally limited by weak emission intensity, thus requiring many labeled target molecules to combine their output to achieve higher signal-to-noise. Wedescribe how the synergistic coupling of plasmonic and photonic modes can significantly boost the emission from fluorophores. By optimally matching the resonant modes of a plasmonic fluor (PF) nanoparticle and a photonic crystal (PC) with the absorption and emission spectrum of the fluorescent dye, a 52-fold improvement in signal intensity is observed, enabling individual PFs to be observed and digitally counted, where one PF tag represents one detected target molecule. The amplification can be attributed to the strong near-field enhancement due to the cavity-induced activation of the PF, PC band structure-mediated improvement in collection efficiency, and increased rate of spontaneous emission. The applicability of the method by dose-response characterization of a sandwich immunoassay for human interleukin-6, a biomarker used to assist diagnosis of cancer, inflammation, sepsis, and autoimmune disease is demonstrated. A limit of detection of 10 fg mL-1 and 100 fg mL-1 in buffer and human plasma respectively, is achieved, representing a capability nearly three orders of magnitude lower than standard immunoassays.

Enhancement of pattern quality in maskless plasmonic lithography via spatial loss modulation

Plasmonic lithography, which uses the evanescent electromagnetic (EM) fields to generate image beyond the diffraction limit, has been successfully demonstrated as an alternative lithographic technology for creating sub-10 nm patterns. However, the obtained photoresist pattern contour in general exhibits a very poor fidelity due to the near-field optical proximity effect (OPE), which is far below the minimum requirement for nanofabrication. Understanding the near-field OPE formation mechanism is important to minimize its impact on nanodevice fabrication and improve its lithographic performance. In this work, a point-spread function (PSF) generated by a plasmonic bowtie-shaped nanoaperture (BNA) is employed to quantify the photon-beam deposited energy in the near-field patterning process. The achievable resolution of plasmonic lithography has successfully been enhanced to approximately 4 nm with numerical simulations. A field enhancement factor (F) as a function of gap size is defined to quantitatively evaluate the strong near-field enhancement effect excited by a plasmonic BNA, which also reveals that the high enhancement of the evanescent field is due to the strong resonant coupling between the plasmonic waveguide and the surface plasmon waves (SPWs). However, based on an investigation of the physical origin of the near-field OPE, and the theoretical calculations and simulation results indicate that the evanescent-field-induced rapid loss of high-k information is one of the main optical contributors to the near-field OPE. Furthermore, an analytic formula is introduced to quantitatively analyze the effect of the rapidly decaying feature of the evanescent field on the final exposure pattern profile. Notably, a fast and effective optimization method based on the compensation principle of the exposure dose is proposed to reduce the pattern distortion by modulating the exposure map with dose leveling. The proposed pattern quality enhancement method can open new possibilities in the manufacture of nanostructures with ultrahigh pattern quality via plasmonic lithography, which would find potentially promising applications in high density optical storage, biosensors, and plasmonic nanofocusing.

Tuning Light–Matter Interactions with Mid-Infrared Plasmonic Coaxial Apertures

Thin plasmonic coaxial apertures have unique optical properties, including extraordinary light transmission and confinement, that can enhance light–matter interactions and can be applied for sensing applications. Here, we use finite-difference time-domain simulations to investigate the mid-infrared optical response of coaxial aperture arrays, consisting of a combination of disk arrays and perforated films of periodically arranged holes. We find that the plasmon response of these arrays is governed by the disk size with little influence from the hole size, with surface plasmon excitation around the circumference of the disks mediating extraordinary optical transmission and strong near-field enhancements. The simulations also predict that light–matter coupling with the vibrational modes of a poly(methyl methacrylate) film placed inside the coaxial apertures can be tuned from weak to strong by adjusting the thickness of the coaxial aperture array’s metal film. Such open structures that can promote tailored light–matter interactions are therefore attractive target platforms for plasmon-enhanced sensing and polaritonic chemistry.

High-Figure-of-Merit Biosensing and Enhanced Excitonic Absorption in an MoS2-Integrated Dielectric Metasurface.

Among the transitional metal dichalcogenides (TMDCs), molybdenum disulfide (MoS2) is considered an outstanding candidate for biosensing applications due to its high absorptivity and amenability to ionic current measurements. Dielectric metasurfaces have also emerged as a powerful platform for novel optical biosensing due to their low optical losses and strong near-field enhancements. Once functionalized with TMDCs, dielectric metasurfaces can also provide strong photon-exciton interactions. Here, we theoretically integrated a single layer of MoS2 into a CMOS-compatible asymmetric dielectric metasurface composed of TiO2 meta-atoms with a broken in-plane inversion symmetry on an SiO2 substrate. We numerically show that the designed MoS2-integrated metasurface can function as a high-figure-of-merit (FoM=137.5 RIU-1) van der Waals-based biosensor due to the support of quasi-bound states in the continuum. Moreover, owing to the critical coupling of the magnetic dipole resonances of the metasurface and the A exciton of the single layer of MoS2, one can achieve a 55% enhanced excitonic absorption by this two-port system. Therefore, the proposed design can function as an effective biosensor and is also practical for enhanced excitonic absorption and emission applications.

Recent progress of gold nanostructures and their applications.

For noble metals, such as gold (Au) and silver (Ag), it is well-known that surface plasmons of their nanocrystals have significant spatial confinement and propagation loss due to the strong damping effect and the scattering between the plasmons and phonons. Noble metal nanostructures are usually referred to as "plasmonic nanostructures" in many studies. Based on the resonance effect of surface plasmons, the electromagnetic field can be localized on the subwavelength scale, which induces a booming new field of nanophotonics. Among the various nanostructures, Au nanostructures have received extensive attention both in fundamental research and technological fields due to their unique localized surface plasmon characteristics. These characteristics include strong optical extinction, near-field enhancement, and far-field scattering. By changing either the morphological parameters or the surrounding medium of nanostructures, the localized surface plasmon resonance (SPR) of Au nanostructures can be tuned in a large spectral region from visible to near infrared (Vis-NIR) wavelength. Corresponding to the experimental research, there are several numerical techniques that enable modeling the optical characteristics of Au nanostructures in different shapes and assemblies. The most popular technique is the finite-difference time-domain (FDTD) method for modeling various nanostructures and nanoscale optical devices. The accuracy of the computational models has been proven by reliable experimental data. In this review, we focused on Au nanostructures of different morphologies, such as nanorods, nanocubes, nanobipyramids and nanostars. Then combined with FDTD simulations, we described the effect of morphological parameters and the surrounding medium on the SPR properties of Au nanostructures. More and more achievements indicate that the surface plasmon effect is promising in many technical fields. In the last part, we summarize some typical applications of plasmonic Au nanostructures, such as high sensitivity sensors, photothermal conversion with hot electron effects and photoelectric devices, as well as plasmonic nanolasers.

Oblique-Incidence-Excited Localized Hot Spots in Plasmonic Particle-on-Film Nanocavities

Regarding plasmonic nanocavities formed by particle-on-film, the nanogap hot spots play an essential role in wide applications including plasmon-enhanced spectroscopy, ultrasensitive sensing, photovoltaics, and photocatalysis. However, hot spots at the nanogap are symmetrically distributed on both sides of the junction under normal incidence. Herein, under the condition of oblique incidence, properties of plasmonic hot spots in the Au@SiO2 particle-on-film have been investigated theoretically. We find that when the plane wave is incident obliquely, the hot spots in the gap are not only symmetrically distributed on both sides of the contact point but also circularly distributed around the junction at specific excitation wavelengths. With the adjustment of the incidence angle, the maximum surface-enhanced Raman spectroscopy enhancement factor from this circularly distributed hot spot reaches 11.3 orders in magnitude. Moreover, the resonant mode at 785 nm has been readily matched by optimizing the size of the Au core, and the optimal thickness of the silica shell with 1 nm for achieving the maximum electromagnetic (EM) field enhancement was further demonstrated. These findings offer a new strategy for manipulating locations of localized hot spots with strong near-field enhancement in plasmonic nanocavities.

Giant Enhancement of Second-Harmonic Generation in Hybrid Metasurface Coupled MoS2 with Fano-Resonance Effect

Plasmonic nanostructures have been regarded as potential candidates for boosting the nonlinear up-conversion rate at the nanoscale level due to their strong near-field enhancement and inherent high design freedom. Here, we design a hybrid metasurface to realize the moderate interaction of Fano resonance and create the dual-resonant mode-matching condition to facilitate the nonlinear process of second harmonic generation (SHG). The hybrid metasurface presents dipolar and octupolar plasmonic modes near the fundamental and doubled-frequency wavelengths, respectively, further utilized to enhance the SHG of low-dimensional MoS2 semiconductors. The maximum intensity of SHG in hybrid metasurface coupled MoS2 is more than ten thousand times larger than that of other structure-units coupled MoS2. The conversion efficiency is reported to be as high as 3.27 × 10−7. This work paves the way to optimize nonlinear light–matter interactions in low-dimensional structures coupled with semiconductors.