Abstract
The optical response of properly excited periodically arranged plasmonic nanostructures is known to demonstrate sharp resonance features associated with high-Q collective modes demanding for various applications in light–matter interaction, filtering and sensing. Meanwhile, practical realization and replication of plasmonic platforms supporting high-Q modes via scalable inexpensive lithography-free approach is still challenging. Here, we justify direct ablation-free irradiation of Si-supported thin Au film by nanojoule-energy femtosecond laser pulses as a single-step and scalable technology for realization of plasmonic metasurfaces supporting collective plasmonic response. Using an adjustable aperture to control and upscale the size of the fabricated nanostructures, nanobumps and nanojets, we demonstrated plasmonic metasurface supporting collective resonances with a moderately high Q-factor (up to 17) and amplitude (up to 45%) within expanded spectral range (1.4–4.5 µm). Vacuum deposition of thin films above the as-fabricated nanostructure arrays was demonstrated to provide fine tuning of the resonance position, also expanding the choice of available materials for realization of plasmonic designs with extended functionality.
Highlights
Received: 24 January 2022Coupling of the propagating electromagnetic waves into resonant oscillations of free electron plasma (surface plasmons (SPs)) propagating at the interface of the noble metal and dielectric is widely used to enhance light–matter interaction in novel optoelectronic devices, metasurfaces and chemo- and biosensors [1–6]
On-demand tunability of the nanobump geometry provides the way for single-step direct laser fabrication of the nanostructure arrays supporting collective plasmonic resonances (CPRs) with a high Q-factor and resonance amplitude within expanded spectral range (1.4–4.5 μm)
A typical view of the nanostructure arrays is given by the scanning electron microscope (SEM) images on the inset of Figure 1a
Summary
Coupling of the propagating electromagnetic waves into resonant oscillations of free electron plasma (surface plasmons (SPs)) propagating at the interface of the noble metal and dielectric is widely used to enhance light–matter interaction in novel optoelectronic devices, metasurfaces and chemo- and biosensors [1–6]. The mentioned features reduce the tuning range of the CPR supported by the nanobump array, limiting the performance and practical applicability of such a plasmonic platform We addressed these issues, showing that the geometry of the laser-fabricated nanobumps (nanojets) can be upscaled by expanding the lateral size of the laser beam through the effective numerical aperture of the focusing lens. On-demand tunability of the nanobump geometry provides the way for single-step direct laser fabrication of the nanostructure arrays supporting CPRs with a high Q-factor (up to 17) and resonance amplitude (up to 45%) within expanded spectral range (1.4–4.5 μm). Vacuum deposition of thin films above the fabricated nanobump arrays provides an additional way for fine tuning the CPR position, allowing the creation of advanced plasmonic designs with extended functionality
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