Two‐Tier Nanolaminate Plasmonic Crystals for Broadband Multiresonant Light Concentration with Spatial Mode Overlap

Abstract

scattering, photoluminescence, and electroluminescence. [4][5][6][7][8] Nevertheless, for many nonlinear nanophotonics applications, it is highly desirable to use multiresonant plasmonic devices that can simultaneously enhance multiphoton excitation/emission processes in several different wavelength bands at the same hotspot locations. [9][10][11][12][13][14][15][16][17][18][19] For constructing multiresonant plasmonic devices, a general approach is to assemble multiple building-block plasmonic resonators within a very close distance; and the optical coupling between spectrally matched non-orthogonal elementary modes of building blocks can result in multiple hybrid plasmonic modes of different resonance wavelengths that spatially overlap. [20][21][22] Based on the geometrical configuration of building-block resonators, multiresonant plasmonic devices can be classified into three types: 1) in-plane arrangement, [9,11,12,15,18,[23][24][25][26][27] 2) core-shell arrangement, [14,[28][29][30][31][32] and 3) out-of-plane arrangement. [33][34][35][36][37] Since it is straightforward to create plasmonic systems with accurate nanoscale control of planar geometries by top-down nanolithography, most previous studies have focused on developing in-plane multiresonant plasmonic devices. [9,11,12,15,18,[23][24][25][26][27] Despite the simplicity in design and fabrication, in-plane multiresonant plasmonic devices face two severe limitations due to the planar layout of multiple building-block resonators. 1) The device footprint tends to be large, and accordingly, the surface density of multiresonant hotspots is typically low; 2) Since the nearest-neighbor coupling of elementary modes dominates between in-plane arranged building-block resonators, the planar multiresonant systems usually support a limited number (<4) of hybridized plasmonic modes with spatial overlaps. Recently, Reshef et al. demonstrated that using in-plane plasmonic metasurfaces with a finite out-of-plane dielectric cladding can increase the number of modes by creating several Fabry-Perot-like (FP-like) resonances. [38] However, such a method primarily depends on the broad electric dipolar plasmonic modes, limiting the maximum attainable absorption to 50% [39] and keeping the field enhancement factor relatively small compared to nanogap plasmonic modes. [20] As the second type of multiresonant plasmonic devices, chemically synthesized core-shell metalinsulator-metal (MIM) multilayered nanoparticles can support multiple hybrid modes by mixing the elementary modes at Effective trapping and nanolocalization of different colored photons simultaneously at the same position remain a challenge in nanophotonics research but can boost applications based on nonlinear multiphoton processes. For achieving broadband nanoscale light concentration, a promising strategy is to employ multiresonant plasmonic devices that support multiple hybridized surface plasmon modes with spatial overlap at several different resonance wavelengths. However, high-order plasmonic modes from hybri...

Nanolaminate Plasmonic Substrates for High-Throughput Living Cell SERS Measurements and Artificial Neural Network Classification of Cellular Drug Responses

“…Figure shows the three major steps to achieve in situ label-free SERS analysis of living cancer cells in response to different drug dosages, and we compare the performance among six different ML methods for multiclass classification of measured SERS data sets from living cells. First, to induce a tight physical coupling between hotspots and cells, we employed top-down fabricated scalable nanolaminate SERS substrates consisting of dense, uniform, and intense hotspot arrays on polymer nanopillar arrays (Figure A). , Nanolaminate metal–insulator–metal (MIM) nanostructures can support multiple plasmonic modes to produce dense nanoplasmonic hotspot arrays with high SERS EF (>10 7 ). ,, 3D protruding nanopillar structures can induce cell engulfment behaviors, resulting in tight hotspot–cell coupling. Second, we performed in situ 2D SERS measurements of living cancer cells directly cultured on nanolaminate SERS substrates with different drug dosages, providing 10,000 spectra (10 ms per spectrum) in less than 3 min (Figure B).…”

Microporous Multiresonant Plasmonic Meshes by Hierarchical Micro–Nanoimprinting for Bio‐Interfaced SERS Imaging and Nonlinear Nano‐Optics

“…The metal and dielectric thicknesses were selected to achieve multiresonant plasmonic responses across a broad visible to near-infrared (Vis-NIR) range. [26,27] The cross-sectional scanning electron microscope (SEM) image in Figure 1B depicts NLPCs within the PMMA nanowell arrays. The optical image of NLPCs shows a vivid diffraction pattern, revealing a uniform distribution of periodic nanostructures over a large sample area.…”

“…The modes at 700, 760, and 1070 nm (Figure 2C,D,F) originate from optical hybridization between the delocalized plasmonic modes in the MIM nanolaminated nanohole array and localized plasmonic modes in the MIM nanolaminated nanodisk arrays, enabling the enhancement of linear and nonlinear optical processes over a broad wavelength range. [ 26 ] Figure 2H shows the nonlinear upconversion light emission spectra between 400 and 800 nm under fs pulses at different excitation wavelengths between 1000 and 1500 nm. The spectra exhibit three main components: THG peaks, SHG peaks, and a broadband UCPL feature.…”

“…Nevertheless, for emerging nanophotonics applications involving multiphoton processes, it is crucial to use multiresonant plasmonic nanostructures to simultaneously enhance light–matter interactions in several resonant spectral bands. [ 15–17 ] For example, multiresonant plasmonic enhancement of multiphoton excitation and emission transitions can boost second harmonic generation (SHG) or upconversion photoluminescence (UCPL) signals for deep‐tissue optical sensing and imaging. [ 8,15,18,19 ] Moreover, multiresonant plasmonic nanostructures enable wavelength‐multiplexed multimodal optical operations at the nano‐bio interface.…”

“…[ 15 ] Recently, several multiresonant plasmonic devices have been generated using top‐down fabrication methods such as electron‐beam lithography, [ 22 ] focused ion beam, [ 23 ] deep‐ultraviolet lithography, [ 24 ] laser‐direct‐writing, [ 25 ] and nanoimprint lithography (NIL). [ 17 ] Despite significant research efforts, to date, the existing multiresonant plasmonic devices face challenging issues, such as relatively low hotspot density, weak excitability of multipolar modes, and lack of scalable nanofabrication methods compatible with flexible microporous substrates.…”