EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Plasmonic metasurfaces based on the extraordinary optical transmission effect (EOT) can be deliberately designed to efficiently transmit specific spectral bands from the visible to the long-infrared regimes, but can also provide high electric field confinement in regions much smaller than the operation wavelength. Such nano/microphotonic devices (which consist of subwavelength periodically or randomly arranged apertures on ultrathin metallic films) could therefore find applications in important technological fields such as compact biosensing, transmissive colour displays, non-linear optics or enhancement of the Raman signal. However, due to their subwavelength nature, fabrication of EOT metasurfaces operating in the visible and infrared spectral regimes is typically conducted through expensive, micro- and nanofabrication techniques carried out in strict cleanroom environments. Therefore, patterning of large areas required for applications currently dominated by conventional optical elements are translated into several fabrication steps and long lithography writing times: procedures that significantly increase the operation cost and energy consumption to a non-acceptable level for most industrial entities.
In this work, we propose and experimentally demonstrate “on-the-fly” fabrication of EOT plasmonic metasurfaces based on pulsed direct laser writing techniques, exploiting laser-induced ablation of gold. Via carefully adjusting the experimental parameters (namely laser power, spot size, repetition rate and scanning velocity), we have successfully achieved dimensions (aperture sizes and spacing) close to nominal design specifications for a wide variety of devices operating in different spectral bands such as the mid and the long-wave infrared.
In summary, our novel approach to nano/microfabrication of EOT metasurfaces allows for single step ultrafast processing of large areas, which can be scaled up further, offering high reproducibility and versatility in terms of achievable dimensions and hole shapes. Our results open up a new technological direction that puts EOT metasurfaces in a realistic position to compete with classical bulky optical components, while overcoming them in performance.