Infrared (IR) bandpass filters are used as an optical element for multispectral imaging that is increasingly beneficial for a range of applications as diverse as space-based imaging, remote sensing, military target tracking, land mine detection, diagnostic medicine, and environmental monitoring. IR bandpass filters for spectral selectivity are mostly manufactured by using the underlying mechanism of a Fabry-Perot optical cavity formed by IR transparent dielectric stacks. The dielectric stack is composed of a large number of alternating layers of low- and high-indices dielectric materials which are relatively expensive, fragile, and uncommon materials, as compared to the visible spectrum materials with high variability in optical, thermal, and mechanical properties.Recently, various two-dimensional (2D) nanoarchitectures that can control the optical properties through metal deposition-based patterning have been reported such as metallic hole, metallic disk, metallic coaxial aperture, and split-ring resonator. More interestingly, quasi-three-dimensional (quasi-3D) plasmonic nanoantenna, consisting of a dielectric separation layer and a nanoscale gap between metal disk array and metal hole array, offers promising advantages for extending device functionality via structural tuning of device dimensions. The present fabrication techniques to define the nanoarchitectures include electron-beam lithography, focused ion-beam lithography, nanoimprint lithography, and interference lithography. Despite great success over the past decades, these approaches are limited by the laborious, complex, and time-consuming nature of the fabrication techniques, thereby impeding their pragmatic application. To resolve these issues, we introduced a proof-of-concept methodology that enables the physical transfer of metal-dielectric hybrid nanoantennas from their donor Si mold to a foreign receiver substrate in a time- and cost-effective manner. However, the choice of this IR transparent dielectric spacer, such as SU-8 (fracture limit = 2-3 %), remains mechanically limited, yielding a high risk of cracks and defects during debonding process.Herein, we unlock this material limitation and therefore establish a mechanically and optically reliable nanoassembly of quasi-3D metal-dielectric hybrid nanoantennas with a SU-8 dielectric spacer. Computational study based on a finite element analysis provides a route to understand underlying transfer-mechanism of quasi-3D metal-dielectric hybrid nanoantennas and fracture mechanism of the IR transparent brittle material depending on the presence or absence of the stress-absorbing layer, such as polymethyl methacrylate (PMMA), thereby demonstrating manufacturability of mechanically reliable nanoassembly method. Following the complete removal of the stress-absorbing layer, the resulting nanoantennas exhibited a capability of spectral filtering in the IR spectral region with the desired peak transmission and full width at half maximum (FWHM). We also investigated the effect of the structural design of these nanoantennas on IR bandpass filtering, and also validated the experimental results with computational analysis.

Multiple Replication of Quasi-Three-Dimensional Plasmonic Nanoantennas With Tailored Optical Properties

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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