Plasmonic bound states in the continuum to tailor light-matter coupling

Abstract

Plasmon resonances play a pivotal role in enhancing light-matter interactions in nanophotonics, but their low-quality factors have hindered applications demanding high spectral selectivity. Here, we demonstrate the design and 3D laser nanoprinting of plasmonic nanofin metasurfaces, which support symmetry-protected bound states in the continuum up to the fourth order. By breaking the nanofins’ out-of-plane symmetry in parameter space, we achieve high-quality factor (up to 180) modes under normal incidence. The out-of-plane symmetry breaking can be fine-tuned by the nanofins’ triangle angle, opening a pathway to precisely control the ratio of radiative to intrinsic losses. This enables access to the under-, critical, and over-coupled regimes, which we exploit for pixelated molecular sensing. We observe a strong dependence of the sensing performance on the coupling regime, demonstrating the importance of judicious tailoring of light-matter interactions. Our demonstration provides a metasurface platform for enhanced light-matter interaction with a wide range of applications.

Improved In Situ Characterization of Electrochemical Interfaces Using Metasurface‐Driven Surface‐Enhanced IR Absorption Spectroscopy

“…SEIRAS performance can be maximized by utilizing a system that is close to the critical coupling condition. [42,43] Here, the nano-slot metasurface is near the critical-coupling condition with γ e /γ i = 1.2. Thus, when the resonance overlaps with the vibrational mode of adsorbed CO at 2033 cm −1 the coupling between the two resonators leads to a small peak in the reflectance spectrum (Figure 1d), where t was set to 5 nm as an example to visualize the modulation of the resonance.…”

Two‐Photon Polymerization Lithography for Optics and Photonics: Fundamentals, Materials, Technologies, and Applications

“…[622][623][624] Combining the advantages of both plasmonic structures and dielectric BIC antennas, the plasmonic BIC phenomenon realized high Q-factor and strong field enhancement simultaneously, pave the way for next-generation optical sensing and spontaneous emission. [615,622,625,626] As shown in Figure 13b, the quasi-BIC mode gradually appears when nanostructures coated with gold are illuminated with oblique incidence. Similar as the plasmonic nanoantenna, the field enhancement is as high as 10, 000 times, meanwhile, the high Q-factor is remained.…”

Ultrasensitive Molecular Fingerprint Retrieval Using Strongly Detuned Overcoupled Plasmonic Nanoantennas

“…[6] In particular, the emergence of PNAs solves the limitation of the low sensitivity of infrared spectroscopy when detecting a small number of molecules or ultra-thin film systems [7][8][9][10] and injects new vitality into traditional infrared spectroscopy techniques. Consequently, PNAs have been widely used in sensing fields involving molecular vibrations, including dynamic reaction monitoring, [11][12][13] hyperspectral infrared imaging, [14][15][16] and biochemical molecular detection. [17][18][19] However, the bandwidth of PNAs with enhancement effects is limited because the spectral resonances (𝜔 0 ) produced by PNAs are sharp and high-Q (quality factor).…”

“…Similarly, pixelated arrays can also ob- tain bandwidth, in which each PNAs array only detects a limited band, and the discrete bands are spliced into broadband by pixelation. [14,16] Another way is to obtain bandwidth by modulation, including angle-multiplexing metasurfaces [22] and tunable graphene. [17,23] These methods employ single-pixel PNAs to collect broadband spectral data by modulating resonance peaks.…”