Large‐Area Resonance‐Tuned Metasurfaces for On‐Demand Enhanced Spectroscopy

Abstract

We show an effective procedure for lateral structure tuning in nanoimprint lithography (NIL) that has been developed as a vertical top-down method fabricating large-area nanopatterns. The procedure was applied to optical resonance tuning in stacked complementary (SC) metasurfaces based on silicon-on-insulator (SOI) substrates and was found to realize structure tuning at nm precision using only one mold in the NIL process. The structure tuning enabled us to obtain fine tuning of the optical resonances, offering cost-effective, high-throughput, and high-precision nanofabrication. We also demonstrate that the tuned optical resonances selectively and significantly enhance fluorescence (FL) of dye molecules in a near-infrared range. FL intensity on a SC metasurface was found to be more than 450-fold larger than the FL intensity on flat Au film on base SOI substrate.

Overcoming metal-induced fluorescence quenching on plasmo-photonic metasurfaces coated by a self-assembled monolayer

“…17,18,20,21 Since the 1980s, attempts were made to suppress metal-induced FL quenching through the introduction of nm-thick spacers between the metallic surface and FL molecules. 1-3 To meet the practical requirements of future applications, it is necessary to establish highly reliable (or reproducible), efficient, feasible (or positioning-free), and cost-effective platforms for FL sensing.…”

“…[1][2][3] To meet the practical requirements of future applications, it is necessary to establish highly reliable (or reproducible), efficient, feasible (or positioning-free), and cost-effective platforms for FL sensing. [14][15][16][17][18][19][20][21] Further requirements for the feasibility and the uniform enhancing response limit the potential candidates. Photobleaching is intrinsic to the molecules and can reduce FL signals in the time spans within several tens of seconds to minutes.…”

“…When considering highly efficient FL sensing, one faces fundamental issues that possibly reduce the FL yield of molecules, including photobleaching of the FL molecules, 4-7 FL reduction by contacting surfaces 8 and metal-induced FL quenching on the plasmonic structures 9-13 that comprise the metallic nanostructures. 17,18,20,21 Since the 1980s, attempts were made to suppress metal-induced FL quenching through the introduction of nm-thick spacers between the metallic surface and FL molecules. Metal-induced FL quenching is an obstacle to significant FL enhancement employing plasmonic resonances.…”

Optical-signal-enhancing metasurface platforms for fluorescent molecules at water-transparent near-infrared wavelengths

“…The PlasPh metasurfaces have been reported to have tunable resonances in a wide wavelength range from the visible to the near-infrared telecom ranges. 20,21 The PlasPh metasurfaces have been found to be highly suitable for enhanced spectroscopy of uorescent molecules around the visible range. [20][21][22][23] For other metallic nanostructures, it is usually quite demanding to ensure tunability of the operating wavelength and, at the same time, capability for high-efficient enhancement.…”

“…20,21 The PlasPh metasurfaces have been found to be highly suitable for enhanced spectroscopy of uorescent molecules around the visible range. [20][21][22][23] For other metallic nanostructures, it is usually quite demanding to ensure tunability of the operating wavelength and, at the same time, capability for high-efficient enhancement. In this respect, photonic-crystal-based platforms 24 are different, because they allow to scale the operating wavelengths, though photonic crystals tend to show weaker enhancement than plasmonic platforms.…”